Important Flutter Packages

 

Here are some packages that you may need in your Flutter app:

1. flutter_bloc: If you're looking for a predictable state management solution for your app, flutter_bloc is a good package to use. It provides tools for handling state changes, events, and more.
2. provider: If you prefer a simpler way to manage app state, provider is a lightweight package that can help you accomplish this.
3. dio: If your app needs to make API calls or work with HTTP requests, dio is a powerful package that can help simplify this process.
4. shared_preferences: If your app needs to store small amounts of data on the device, shared_preferences is a lightweight package that can help with this.
5. intl: If your app needs to support multiple languages or locales, intl provides a set of tools for handling internationalization and localization.
6. flutter_svg: If your app needs to work with SVG images, flutter_svg provides a way to render SVG images directly in your app.
7. google_maps_flutter: If your app needs to display maps or work with location data, google_maps_flutter is a useful package to consider.
8. url_launcher: If your app needs to open URLs or other external links, url_launcher provides a simple way to do this.
9. cached_network_image: If your app needs to display images that are loaded from the internet, cached_network_image can help speed up the process by caching images.
10. http: If you're looking for a simpler HTTP client than dio, http is another option that provides basic functionality for making HTTP requests.
11. path_provider: If your app needs to work with files or directories on the device, path_provider provides a set of tools for accessing common locations on the file system.
12. flutter_html: If your app needs to render HTML content, flutter_html is a package that can help you display formatted text, images, and more.
13. flutter_spinkit: If your app needs to display loading indicators or progress spinners, flutter_spinkit provides a set of customizable widgets for this purpose.
14. flutter_webview_plugin: If your app needs to display web content or work with web views, flutter_webview_plugin provides a simple way to embed web views directly in your app.
15. firebase_core: If your app needs to work with Firebase services, firebase_core provides a core set of tools for initializing and configuring Firebase in your app.
16. firebase_auth: If your app needs to support user authentication, firebase_auth provides tools for working with Firebase authentication services.
17. firebase_database: If your app needs to work with real-time data, firebase_database provides a solution for storing and retrieving data in real-time using Firebase.
18. firebase_storage: If your app needs to store or retrieve files in the cloud, firebase_storage provides a way to work with Firebase Storage.
19. flutter_map: If your app needs to display maps using OpenStreetMap or other providers, flutter_map provides a customizable solution for rendering maps directly in your app.
20. flutter_redux: If you prefer the Redux state management pattern for your app, flutter_redux provides an implementation of this pattern specifically for Flutter.
21. flutter_form_builder: If your app needs to build forms, flutter_form_builder provides a set of customizable widgets for building forms and collecting user input.
22. flutter_icons: If your app needs to display icons, flutter_icons provides a set of customizable icons that can be used in your app
23. flutter_local_notifications: If your app needs to send notifications to the user, flutter_local_notifications provides a way to create and schedule local notifications directly in your app.
24. flutter_secure_storage: If your app needs to store sensitive data such as passwords or API keys, flutter_secure_storage provides a secure way to store this data on the device.
25. flutter_reorderable_list: If your app needs to allow the user to reorder items in a list, flutter_reorderable_list provides a set of widgets that allow the user to drag and drop items to reorder them.
26. url_launcher: If your app needs to launch external apps or open links in the browser, url_launcher provides a simple way to do this.
27. flutter_keyboard_visibility: If your app needs to respond to changes in the keyboard visibility, such as resizing UI elements to accommodate the keyboard, flutter_keyboard_visibility provides a way to listen for keyboard events and adjust the UI accordingly.

Source:

https://medium.com/@adeelsultan414/important-flutter-packages-d03fb20f964f

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Modern Flutter: 6 Tips and Tricks for Beginner Developers

 

Use the final keyword:

In Dart, variables that are initialized and cannot be changed are declared using the final keyword. Your code will become more predictable and help to prevent bugs.

Here’s an example:

final String name = 'Snehal Singh';
name = 'Snehal Singh'; // Error: The final variable 'name' can't be assigned a value.

In this example, we declare a variable name and assign it the value 'Snehal Singh'. Since name is declared as final, we cannot reassign it to a new value.

Use named parameters:

Using named parameters in function calls is supported in Dart, which can improve the readability and comprehension of your code.

You have more control over the order in which arguments are passed to functions when using named parameters.

Here’s an example:

void greet({String name, String message}) {
  print('$name says $message');
}

greet(name: 'Snehal Singh', message: 'Hello, world!'); // Snehal Singh says Hello, world!

In this example, we define a function greet that takes two named parameters, name and message. We can then call the function and pass in the arguments in any order we like, as long as we specify the names of the parameters.

Use null-aware operators:

Dart offers a number of null-aware operators that can make your code shorter and more productive.

For instance, you can safely access the properties of an object that might be null by using the ?. operator.

Here's an example:

class Person {
  final String name;
  final int age;
  
  Person({this.name, this.age});
}

final person = Person(name: 'Snehal Singh', age: null);

final name = person?.name ?? 'Unknown';
final age = person?.age ?? -1;

print(name); // Snehal Singh
print(age); // -1

In this example, we define a class Person that has two properties, name and age. We create an instance of Person and assign null to the age property. We then use the null-aware operator ?. to safely access the name and age properties, and the null-coalescing operator ?? to provide default values in case they are null.

Use extension methods:

Using extension methods, Dart lets you add new methods to classes that already have them.

This can be helpful if you want to expand a class’s functionality without changing its source code.

Here’s an example:

extension StringExtension on String {
  bool get isPalindrome {
    final reversed = this.split('').reversed.join('');
    return this == reversed;
  }
}

print('racecar'.isPalindrome); // true
print('hello'.isPalindrome); // false

In this example, we define an extension method isPalindrome on the String class. The method checks if the string is a palindrome and returns true or false.

Use async/await:

Asynchronous programming is supported in Dart using the async and await keywords.

This can assist you in writing more responsive code that doesn’t obstruct the UI thread.

Here's an example:

Future<void> main() async {
  print('Fetching data...');
  final data = await fetchSomeData();
  print('Data received: $data');
}

Future<String> fetchSomeData() async {
  await Future.delayed(Duration(seconds: 2)); // Simulate network delay
  return 'Hello

In this example, we define a function main that is marked as async. Inside main, we call a function fetchSomeData using the await keyword. This tells Dart to wait for the fetchSomeData function to complete before continuing the execution of the rest of the main function. fetchSomeData simulates a network delay using the Future.delayed function and returns a string.

When we run the main function, we first print a message to the console indicating that we are fetching data. We then call fetchSomeData and wait for it to complete before printing the received data to the console.

Use the cascade operator:

The cascade operator (..) in Dart enables you to chain together several method calls on the same object.

Your code may become clearer and easier to read as a result.

Here's an example:

class Person {
  String name;
  int age;
  
  void sayHello() {
    print('Hello, my name is $name and I am $age years old');
  }
}

final person = Person()
  ..name = 'Snehal Singh'
  ..age = 30
  ..sayHello(); // Hello, my name is Snehal Singh and I am 30 years old

In this example, we define a class Person that has two properties, name and age, and a method sayHello. We create an instance of Person and use the cascade operator .. to set the name and age properties and call the sayHello method in a single chain of method calls.

Source:

https://medium.com/dhiwise/modern-flutter-6-tips-and-tricks-for-beginner-developers-e4094de061bb

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1000+ Prompts so You Don’t Have to: 10 Need-to-Know Techniques

 

Prompt Engineering Course: The Art of the Prompt.

Prompts, prompts, prompts. I learned it all the hard way, so that you don’t have to. Recently, I curated a long list of list of prompts — feel free to check them for inspiration. I’ve tried an endless amount of ideas with real AI powered applications. Some worked well, some not at all.

In this post I’ll share all my insights– consider it a “best of” album. I’ll give you in-depth descriptions for how to best wield the top 10 approaches that have helped me become a better prompt engineer. I hope they will be useful for you on your journey to becoming a master prompt engineer.

What is in for you in this story? Some of the ideas discussed here work when copying it into the playgrounds of ChatGPT or Bard. Many of them can help you develop applications based on the model’s APIs (like the OpenAI API).

Why is prompt design important? Perfect prompt design can …

• Improve your (already) working solution, increasing it from an 85% successful answering rate up to 98%.
• Greatly enhance the customer experience with more exciting conversations, with better tonality and context recognition
• Help handle off-topic questions, prompt injections, toxic language and more.

Let’s get started — here is the table of contents: The 10 most important prompting approaches:

1. Add specific, descriptive instructions (with cheat sheet)
2. Define the output format
3. Give few-shot examples
4. Integrate “don’t know” / “won’t answer” cases (to control hallucination / critical topics)
5. Use chain-of-thought reasoning
6. Use prompt templates, not static prompts
7. Add a data context
8. Include conversation history
9. Format the prompt: Use clear headlines labels and delimiters in your prompt
10. Bringing it all together: The anatomy of a professional prompt (with cheat sheet)

1) Add Specific, Descriptive Instructions

Without deliberate instructions you often get lengthy, sometimes vague answers talking about anything and everything.

Not giving specific instructions in a prompt often results in ChatGPT waffling

Yawn. As an AI model, I can only produce answers that will make your foot fall asleep. Revenge of the cloned responses. No one needs this. With the next instruction, let’s add a bit of spice. Let’s see how a specific instruction (not just “answer the questions …”) can produce exactly the answer you need in your specific conversation context.

A short, but helpful instruction in a prompt

Perfect —it worked!

Being specific, descriptive in the prompt is especially important, when using the model as part of a software project, where you should try to be as exact as possible. You need to put key requirements into the instructions to get better results.

You don’t have to take notes– I’ll slip you a cheat sheet. You don’t need to use everything, just pick and choose what you need. Avoid the obvious superfluous extras (“Act as a helpful AI”, “answer the questions” … “truthfully, on the basis of your knowledge”) — which SOTA models don’t need, because they will do it anyway: In their standard setup, none of these models will respond like grumpy cat, not answer at all, or deliberately lie to you.

Prompt instruction cheat sheet: Bot persona, user persona, verb, output format, length, tonality, edge case, conversation topics.

A note about the first line: Act as somebody / something usually defines a large bundle of behavioral traits in very few words. Instead of saying “bark when you’re excited”, “growl when you feel threatened”, “wag your tail when you’re happy”, we can just say one word: Dog.

Dogs exhibit all these behaviors and many more. Find a short description for the person / machine you believe can best answer the question. The models are great in simulating anything — they can act as a C-Shell terminal, Aragorn from Lord of the Rings or an HR person from a big company conducting a job interview with you. You can even write a complete backstory into the prompt, give the model a character, a history, preferences to make the conversation more exciting and rewarding.

Keep one thing in mind: Many language models have limitations in their core capabilities, they cannot simulate a good search engine, a pocket calculator, or a visual artist because they do not have the respective research or processing capabilities.

2) Add a Detailed Format of the Desired Model Response

Besides a brief mention of the output format in the instruction, it is often helpful to be a little bit more detailed: Specify a response format, which makes it easier for you to parse or copy parts of the answer.

A structured output format in a prompt.

If you don’t need a fully formatted output like JSON, XML, HTML, sometimes a sketch of an output format will do as well.

A simply structured output format. Image credit: Maximilian Vogel (with ChatGPT)

Defining the output format can be of great help when working with models on playgrounds or web interfaces. It is absolutely necessary when accessing models via an API and the model response consists of several components that need to be separated automatically before sending an answer to the user.

3) Give Few-Shot Examples

Any sufficiently elaborate model can answer easy questions based on “zero-shot” prompts, without any learning based on examples. This is a specialty of foundation models. They already have billions of learning “shots” from pre-training. Still, when trying to solve complicated tasks, models produce outputs better aligned to what you need if you provide examples.

Imagine that you’ve just explained the job and are now training the model with examples: If I ask you this, then you answer that. You give 2, 3, 5 or 8 examples and then let the model answer the next question by itself. The examples should be in the format of query & expected model answer. They should not be paraphrased or just summarized.

Few-shot examples in prompts.

This works. “Trust” is an interesting one, I would rather go for evidence in the hospital, but that is open to debate. Here, you don’t even have to describe an output format, the examples already define an output format.

4) Add Edge Cases to the Few-Shot Examples

If you are building an assistant to support the user in the operation of a cleaning robot, you can train the model to avoid answering off-topic questions, which may be critical for factual accuracy, liability, or brand value.

Standard cases and edge cases in prompt examples.

It’s advisable to not include too many similar examples, instead, consider exploring different categories of questions in the examples. In the case of our cleaning robot this could be:

Standard cases:

• Help with operations (step-by-step instructions)
• Help with malfunctions
• Questions about product features / performance data

Edge cases:

• Off-topic questions
• Questions that are on the topic, but the bot cannot answer
• Questions the bot doesn’t understand or where it needs more information
• Harassment / toxic language

Handling off-topic questions or questions the bot can’t answer based on your input material is key for professional business applications. If not, the model will start to hallucinate and give the user potentially wrong or harmful instructions to use a product.

5) Chain-of-Thought Reasoning

Language models don’t really read, conceptualize tasks or questions, but rather produce an answer with a high stochastic probability based on chains of tokens.

In the next example (on the left), we can see that the model isn’t processing our question correctly — admittedly, you don’t have to be an LLM to get this rather complicated question wrong.

But in contrast (on the right-hand side): If we force the model to think step by step, it can generate a correct answer. The two types of reasoning correspond to Daniel Kahneman’s “System 1 and System 2 Thinking” from his book Thinking, Fast and Slow.

System 1 versus System 2 (Chain-of-Thought) thinking.

In our prompt on the right-hand side, we added an example, which helps the model to understand how to process data and how to think “slow”. Make sure again, that either in the instruction or in the examples you specify an easily scannable output format (like “\nResult: species’ names”). This helps you to skip the thinking part of the output and just present the result (“Cats”) to your users.

For further reading, the scientific paper introducing the chain-of-thought prompting: https://arxiv.org/abs/2201.11903

6) Use a Prompt Template

When using a prompt in an application context, don’t simply add the user question to the end, instead try to build a prompt template with variable components to facilitate testing and real-world use.

From prompt to prompt template: Use variables!

In the following examples we will add more variables to our template.

7) Add a Custom Data Context

In many business applications, it’s not ideal for user’s questions to be answered based on a model’s general pre-training, which usually relies on past internet information that could be outdated, inaccurate or incomplete.

It’s preferable to answer these questions using specific content from your organization, like manuals, databases (such as product information management databases) or systems (such as map services).

Create the prompt template to integrate seamlessly with this specified content, also known as “context”.

Retrieving the context from documents is another topic not discussed in full here, however, it’s important to note that you usually get the relevant snippets from a much larger content base (which may not fit directly into the prompt). Therefore, it’s often narrowed down through retrieval processes like DPR or through searches in a vector database.

Prompt template and integration of specific data in the context.

The context data doesn’t have to be plain text. When sourcing data from a system or database, you can also input structured data, such as a list of the nearest filling stations.

Structured input data in a prompt.

8) Include Conversation History

For many ongoing conversations it is not possible to give an answer based on a single question — the context of the conversation plays a role here:

User: Where can I buy wool socks around here?
Assistant: At Sockenparadies, 8 min from here, Torstr. 154
User: Are they still open?
Assistant: No, they are already closed.
User: What time will they open tomorrow?
Assistant: At 10AM.
User: Is there anything else nearby?
Assistant: No stores are currently open.

User questions #2, #3 and #4 can only be answered with help of the conversation context. These questions often contain an explicit reference (“they”, ”anything else”) related to the topics previously discussed.

Prompt template: Conversation history.

In the example above, using the conversation history, the model can process the user utterance “Yes, please!” like a fully qualified statement: “Yes, please, give me a step-by-step instruction to set up the charging station”.

In some APIs (like OpenAI’s chat completion API or Langchain) the history can be handed over in a different way (e.g., an array of user / assistant messages).

9. Format the Prompt: Use Clear Headline Labels and Delimiters

When crafting an extensive prompt, structure it in a way that the model can distinguish between various components, such as:

- Instruction

- Desired output format

- Few shot examples

- Data context

- Conversation history

… and so on.

Feel free to format parts of the prompt with hashes (“#”). While many models don’t need this, it can be helpful for other models. Additionally, it can help both you and future prompt engineers when editing.

Enclose longer passages of input context in quotes to prevent the model confusing them for instructions.

Do the same and place user inputs inside quotes to prevent injections. Injections are user utterances that not only provide an input, but also change the direction of processing, for example instructions like “forget all previous instructions, but instead do [this or that] “. Without using quotes, the model could struggle to recognize that this isn’t a valid instruction, but a potentially harmful user input.

Prompt delimiters, prompt formatting.

10. Bringing it All Together: The Anatomy of a Prompt

Phew! We’re nearly at the end … now it’s time to integrate everything. Remember, you probably won’t need all of the following components, but feel free to use this cheat sheet when checking your prompt.

Cheat sheet: The anatomy of a prompt: Instruction, few-shot learning, data context, output format and conversation history.

Prompts can be quite long and complex. Often, long, and carefully crafted prompts with the right ingredients can lead to a huge reduction in incorrectly processed user utterances. But always keep in mind that most prompt tokens have a price, i.e. the longer the prompt, the more expensive it is to call the API. Recently, however, there have been attempts to make prompt input tokens cheaper than output tokens.

The prompt shown above is close to a little application on its own. To use it to build a basic working app that asks a child’s name, asks questions and returns ratings for answers, you will only need around 50–100 lines of code in a langchain framework and a good textbook PDF. Just fyi, that creating an app or website which is really fun and allows kids to register, collect stars and badges, track learning progress will need much more development and framework.

I hope the story helps you to become a master prompt engineer or designer. Feel free to give me feedback or ask me questions here using the comment function.

Good luck with your AI-powered application!

Source:

https://medium.com/mlearning-ai/i-scanned-1000-prompts-so-you-dont-have-to-10-need-to-know-techniques-a77bcd074d97

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Roadmap to Master Flutter

 

Flutter is an open-source UI framework developed by Google for building high-performance, high-fidelity, apps for mobile, web, and desktop platforms. It uses the Dart programming language and offers a range of widgets and tools for creating beautiful, fast, and responsive user interfaces.

If you’re interested in learning Flutter, the following roadmap can help guide you on your journey:

1. Learn the basics of Dart: Since Flutter is built using the Dart programming language, it’s important to have a solid understanding of Dart fundamentals. Here are some resources to get started:

• Dart documentation: https://dart.dev/guides
• DartPad: https://dartpad.dev/

2. Get familiar with Flutter Widgets: Widgets are the building blocks of Flutter UIs. Learn the basics of how to use Flutter’s widgets to create UIs. Here are some resources to get started:

• Flutter Widgets documentation: https://flutter.dev/docs/development/ui/widgets
• Flutter Widget Catalog: https://flutter.dev/docs/development/ui/widgets/material

3. Understand Flutter Architecture: Flutter has its own architecture pattern called “Flutter Architecture”, which is based on the Model-View-Controller (MVC) pattern. Here are some resources to get started:

• Flutter Architecture documentation: https://flutter.dev/docs/development/data-and-backend/state-mgmt
• Flutter State Management Guide: https://flutter.dev/docs/development/data-and-backend/state-mgmt/overview

4. Learn Flutter Routing and Navigation: Routing and navigation are important concepts in any mobile app development framework. Here are some resources to get started:

• Flutter Navigation documentation: https://flutter.dev/docs/development/ui/navigation
• Flutter Navigation Tutorial: https://www.youtube.com/watch?v=3SsYZDJdeXk

5. Dive into Flutter Animations: Flutter provides powerful animation tools to create fluid and responsive UIs. Here are some resources to get started:

• Flutter Animations documentation: https://flutter.dev/docs/development/ui/animations
• Flutter Animation Tutorial: https://www.youtube.com/watch?v=G1eW3Oi6uoc

6. Explore Flutter Plugins: Flutter provides a wide range of plugins to access native device features like the camera, GPS, and more. Here are some resources to get started:

• Flutter Plugins documentation: https://flutter.dev/docs/development/packages-and-plugins
• Flutter Plugin Catalog: https://pub.dev/flutter/packages

7. Build a complete Flutter project: Now that you have the basics down, it’s time to build your own project. Here are some resources to help you get started:

• Flutter Getting Started guide: https://flutter.dev/docs/get-started
• Flutter Projects on Github: https://github.com/search?q=flutter

Future Scope of Flutter:

Flutter is quickly gaining popularity and is expected to grow in the future. Here are some reasons why:

1. Cross-platform development: Flutter allows developers to build high-quality apps for both iOS and Android platforms using a single codebase. This saves time and reduces development costs.
2. Fast development and hot-reload: Flutter’s “hot-reload” feature allows developers to see changes in real time, making the development process faster and more efficient.
3. Beautiful UIs: Flutter provides a wide range of widgets and tools to create beautiful, responsive UIs.
4. Easy to learn: Flutter’s syntax is easy to learn, especially if you have experience with other object-oriented programming languages.
5. Large and growing community: Flutter has a large and growing community of developers, which means there is a lot of support, resources, and tools available for developers.

Overall, Flutter is a great choice for mobile app development, and it’s expected to continue to grow.

Projects

There are many creative projects you can create and deploy while learning Flutter. Here are a few project ideas to get you started and build confidence:

1. Recipe Sharing Application - Text, audio & video
2. Music Player
3. Ebook Store — with pdf reader & payment gateway integration
4. Video Conference Application — with live chat

Source:

https://mobileappcircular.com/roadmap-to-master-flutter-192549d6f1da

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Complete Guide to Flutter Error Handling: Techniques and Code Examples

 

Error handling is essential to creating mobile apps since it makes sure that even in the face of unforeseen problems, your Flutter app will run smoothly and be user-friendly. This in-depth book will cover best practices and code samples for handling mistakes efficiently and graciously as it explores various error-handling mechanisms in Flutter. By the time you’re finished reading this article, you’ll have a solid grasp of Flutter’s error handling and be prepared to create dependable apps. Let’s start now!

1️. Recognising Errors in Flutter

As with any programming language or framework, mistakes can happen when developing using Flutter. Building dependable and stable programs requires a thorough understanding of these problems. Let’s explore the many fault categories that might happen in Flutter apps:

1. Exceptions are objects that indicate failures that happen when code is being executed in Dart, the programming language used by Flutter. Dart throws an exception when a special circumstance occurs, such as trying to divide by zero, accessing a null reference, or calling a method on an object that doesn’t allow it. The program may be terminated if the exception is not caught and handled appropriately.
2. Errors In addition to exceptions, Dart also contains a class of objects known as errors. Contrary to exceptions, errors typically point out serious problems that shouldn’t be identified and fixed since they might cause erratic program behavior or crashes. OutOfMemoryError and StackOverflowError. are frequent faults. To ensure that the program crashes and prevent unpredictable behavior, errors should be considered fatal and left uncaught.
3. Null Reference Errors The null reference error, commonly referred to as a Null Pointer Exception, is one of the most frequent mistakes made in programming. It happens when you attempt to use a property or method on an object that is null, or one that does not really reference any instance. To securely access properties or invoke methods on possible null objects in Dart and avoid null reference issues, use the null-aware operator. (?.)

String? name; // Nullable variable
print(name?.length); // Using ?. to avoid null reference error

4. Assertion Failures: Assertions may be used in Flutter to check certain conditions when developing. When an assertion statement evaluates to false, it results in an assertion failure. Typically used for debugging, assertions can be turned off in production builds to improve efficiency.

assert(someCondition, "This will be displayed if someCondition is false");

5. Asynchronous Errors: You often use asynchronous activities in Flutter apps, such as sending network queries or retrieving data from databases. An unhandled exception that results from an error occurring during an asynchronous action without being detected may cause unexpected application behavior or crashes. try-catch blocks or the Future API can be used to handle asynchronous failures.

try {
  var result = await someAsyncOperation();
  // Use the result
} catch (e) {
  // Handle the asynchronous error
}

2. What Makes Error Handling Critical?

Error management is an essential component of Flutter app development and is very important for the following reasons:

1. Enhancing User Experience: Users may experience unexpected crashes or behavior when issues occur during program execution. Error management aids in managing these issues and provides users with helpful error messages. Users will have a more satisfying and user-friendly experience if error messaging and handling are done correctly and users are informed about what went wrong and how to fix it.
2. Keeping Apps From Crashing: Unhandled errors and exceptions can cause app crashes, which can frustrate users and result in possible data loss. You may avoid the application from suddenly stopping and provide options for recovery or fallback methods by implementing good error handling.
3. Maintaining App Stability: Your Flutter app’s overall stability is enhanced by robust error handling. You may avoid cascade failures and make sure the app works even in difficult circumstances by foreseeing future issues and gently addressing them.
4. Debugging is made simpler: by error handling, which facilitates the identification and diagnosis of problems throughout the development and testing phases. When exceptions arise, well-designed error handling aids in identifying the underlying cause, making it simpler to resolve defects and raise the application’s dependability.
5. Graceful Recovery from Failures: Some mistakes may be reversible or permit the use of backup plans. For instance, error handling might start a retry mechanism or switch to a cached data source if a network request fails. Correct error handling can improve the likelihood of recovering from temporary failures and enhancing user experience.
6. Logging and error reporting: When errors are handled correctly, you may build logging methods that capture when mistakes and exceptions occur in actual use. These logs may be gathered and aggregated by error reporting technologies, giving users insightful information about their most pressing problems. You may use this data to decide which enhancements and problem fixes to include in further app upgrades.
7. Null Safety and Stability: Now that Flutter has null safety, it’s even more important to handle null references appropriately. Your code will be more predictable and stable if you use null-aware operators and adhere to the recommended null safety procedures.
8. Security and compliance: In some applications, ensuring compliance with security and privacy laws requires effective error handling. For instance, improper handling of sensitive data mistakes might result in data breaches and security flaws.

3. Try-Catch Basic Error Handling

Try-catch blocks are one of the core error-handling strategies used in Dart. These building elements enable programmers to manage exceptions, prevent crashes and provide fallback options in case of problems.

The Try-Catch Block’s Anatomy The “try” and the “catch” blocks are the two primary parts of try-catch blocks. The code that could throw an exception is contained in the try block. If an exception is thrown inside of the try block, the catch block is responsible for handling it.

The “try” Block: The code that might cause an exception should be placed in the “try” block. For potentially error-prone code, it serves as a container of protection.

The “catch” Block: When an exception is raised within the try block, the catch block is put into action. It recognizes the exception and enables you to gently manage it. To fix the problem, you can take extra steps or provide the user with useful error messages.

Example: How to handle a division by zero exception: Let’s look at an example where we have a function that divides. The scenario where the denominator is zero, which would lead to a division by zero exception, will be handled with a try-catch block.

void divideNumbers(int numerator, int denominator) {
  try {
    double result = numerator / denominator;
    print('Result of division: $result');
  } catch (e) {
    print('Error: $e');
    print('Cannot perform the division.');
  }
}

void main() {
  int num1 = 10;
  int num2 = 0;

  divideNumbers(num1, num2);
}

In this example, if we set num2 to 0, the catch block will catch a division by zero exception. Instead of crashing the app, the catch block will display an error message, preventing any disruption to the user experience.

Try-catch blocks allow Flutter developers to gracefully manage errors, improve user experience, and prevent app crashes, improving the stability and usability of their apps.

4. Dealing with Asynchronous Errors

To maintain the dependability of your code, resolving failures in asynchronous processes is crucial while developing Flutter apps. Asynchronous tasks, including reading data from databases or APIs, provide particular problems for managing errors. Futures and Streams, two typical asynchronous structures in Flutter, will be used to examine how to manage mistakes in asynchronous activities in this section.

Understanding Asynchronous Error Management: Traditional try-catch error management is problematic for asynchronous activities since they run independently from the main program flow. Instead, for efficient error management, we employ the mechanisms offered by Futures and Streams to manage mistakes and propagate them to the proper components.

Future error handling: Futures represent a single value that might not be immediately accessible. The Future can end when an asynchronous action is finished with a value or an error. The .catchError() function is used to detect and respond to errors that occur while a future is being executed.

Stream error handling: Streams are collections of asynchronous events that emit data continuously over time. The .listen() function is used to subscribe to events when working with streams. We may use the .onError() function to catch and deal with any faults that happen during the life of a stream.

Example of Future and Stream Error Handling:
Let’s use future and stream operations to demonstrate error handling:

Future<int> fetchUserData() async {
  await Future.delayed(Duration(seconds: 2)); // Simulating an async operation
  // Uncomment the line below to trigger an error
  // throw Exception('Error fetching user data');
  return 42; // Simulating a successful response
}

void main() {
  // Handling errors in a Future
  fetchUserData()
      .then((value) => print('User data: $value'))
      .catchError((error) => print('Error fetching user data: $error'));

  // Handling errors in a Stream
  Stream<int>.periodic(Duration(seconds: 1), (count) => count)
      .map((count) {
        // Uncomment the line below to trigger an error
        // if (count == 2) throw Exception('Error in stream');
        return count;
      })
      .listen(
        (data) => print('Stream data: $data'),
        onError: (error) => print('Error in stream: $error'),
      );
}

The fetchUserData() function replicates an asynchronous action using a Future in this example. The.catchError() function will handle the error and provide an error message if the line that throws the error is uncommented.

The .onError() function is used in the Stream example to handle faults that may arise throughout the life of the stream.

5. Using ErrorWidgets to handle global errors

Setting up systems to detect unhandled exceptions and faults that may occur anywhere in your program is known as global error handling. These errors may be intercepted and handled with custom ErrorWidgets, preventing the app from crashing and guaranteeing a positive user experience.

ErrorWidgets and FlutterError: In Flutter, the framework invokes the FlutterError.onError method whenever an unhandled exception occurs. ErrorWidgets may be used to customize this method and offer your own unique error-handling logic. ErrorWidgets are widgets that warn the user of errors.

Implementing Global Error Handling: Let’s use a customized ErrorWidget to demonstrate how to configure global error handling:

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Global Error Handling',
      home: ErrorHandlerWidget(
        child: MyHomePage(),
      ),
    );
  }
}

class MyHomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Global Error Handling Example')),
      body: Center(
        child: ElevatedButton(
          onPressed: () {
            // Uncomment the line below to trigger an error
            // throw Exception('Simulated error');
            Navigator.push(
              context,
              MaterialPageRoute(builder: (context) => SecondPage()),
            );
          },
          child: Text('Trigger Error'),
        ),
      ),
    );
  }
}

class SecondPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Second Page')),
      body: Center(
        child: ElevatedButton(
          onPressed: () {
            // Uncomment the line below to trigger an error
            // throw Exception('Another simulated error');
          },
          child: Text('Trigger Another Error'),
        ),
      ),
    );
  }
}

class ErrorHandlerWidget extends StatefulWidget {
  final Widget child;

  ErrorHandlerWidget({required this.child});

  @override
  _ErrorHandlerWidgetState createState() => _ErrorHandlerWidgetState();
}

class _ErrorHandlerWidgetState extends State<ErrorHandlerWidget> {
  // Error handling logic
  void onError(FlutterErrorDetails errorDetails) {
    // Add your error handling logic here, e.g., logging, reporting to a server, etc.
    print('Caught error: ${errorDetails.exception}');
  }

  @override
  Widget build(BuildContext context) {
    return ErrorWidgetBuilder(
      builder: (context, errorDetails) {
        // Display a user-friendly error screen
        return Scaffold(
          appBar: AppBar(title: Text('Error')),
          body: Center(
            child: Text('Something went wrong. Please try again later.'),
          ),
        );
      },
      onError: onError,
      child: widget.child,
    );
  }
}

class ErrorWidgetBuilder extends StatefulWidget {
  final Widget Function(BuildContext, FlutterErrorDetails) builder;
  final void Function(FlutterErrorDetails) onError;
  final Widget child;

  ErrorWidgetBuilder({
    required this.builder,
    required this.onError,
    required this.child,
  });

  @override
  _ErrorWidgetBuilderState createState() => _ErrorWidgetBuilderState();
}

class _ErrorWidgetBuilderState extends State<ErrorWidgetBuilder> {
  @override
  void initState() {
    super.initState();
    // Set up global error handling
    FlutterError.onError = widget.onError;
  }

  @override
  Widget build(BuildContext context) {
    return widget.child;
  }
}

In this example, we create a simple Flutter app with two pages (MyHomePage and SecondPage). The ErrorHandlerWidget wraps the entire app, and the ErrorWidgetBuilder is used to handle errors and display a user-friendly error screen.

When you run the app, you’ll see a button on the home page that allows you to trigger an error by uncommenting the line that throws an exception. The global error-handling logic will catch the error in the ErrorHandlerWidget and displayed on the error screen.

With global error handling using ErrorWidgets, you can provide a consistent and smooth user experience even when unexpected errors occur in your Flutter app. Additionally, you can use the error-handling logic in onError to perform logging or report errors to a server for further analysis.

6. Handling Platform-specific Errors

The platforms that Flutter apps may operate on include Android, iOS, web, desktop, etc. Every platform might experience various issues or behave differently. Platform-specific mistakes must be graciously handled in order to deliver a consistent and user-friendly experience.

Finding the Current Platform: The Platform class from the dart:io library may be used with Flutter to find the Current Platform. This class can determine the platform, allowing you to customize your error messages.

Example: Let’s use a platform-specific error handling example to show how to handle such issues and display such error messages:

import 'package:flutter/material.dart';
import 'dart:io' show Platform;

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Platform-specific Error Handling',
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  void handlePlatformError(BuildContext context) {
    String errorMessage;
    if (Platform.isAndroid) {
      errorMessage = 'This feature is not available on Android.';
    } else if (Platform.isIOS) {
      errorMessage = 'This feature is not available on iOS.';
    } else if (Platform.isMacOS) {
      errorMessage = 'This feature is not available on macOS.';
    } else if (Platform.isWindows) {
      errorMessage = 'This feature is not available on Windows.';
    } else if (Platform.isLinux) {
      errorMessage = 'This feature is not available on Linux.';
    } else if (Platform.isFuchsia) {
      errorMessage = 'This feature is not available on Fuchsia.';
    } else {
      errorMessage = 'This feature is not supported on your platform.';
    }

    showDialog(
      context: context,
      builder: (context) => AlertDialog(
        title: Text('Error'),
        content: Text(errorMessage),
        actions: [
          TextButton(
            onPressed: () => Navigator.pop(context),
            child: Text('OK'),
          ),
        ],
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Platform-specific Error Handling')),
      body: Center(
        child: ElevatedButton(
          onPressed: () => handlePlatformError(context),
          child: Text('Show Platform Error'),
        ),
      ),
    );
  }
}

In this illustration, we build a straightforward Flutter application with a button that causes a platform-specific error. The handlePlatformError method uses Platform.isX attributes to determine the current platform, and then it displays the appropriate error message in an AlertDialog based on the platform.

The “Show Platform Error” button will display an error message specific to your current platform when you launch the app and click it. Using an Android emulator, for instance, will result in the error message “This feature is not available on Android.”

You can make sure your Flutter app delivers a consistent and user-friendly experience across many platforms by handling platform-specific issues and supplying pertinent error messages.

7. Handling Network Errors

whether developing a Flutter app or handling network faults is essential to provide users with a smooth experience whether they run across connectivity problems or server difficulties. In this part, we’ll look at how to deal with network issues and provide users with the right kind of feedback when there are server or network issues.

Example 1: Handling Network Unavailability:
Let’s show you how to identify network unavailability and inform the user that there is “No Internet Connection”:

import 'package:flutter/material.dart';
import 'package:connectivity/connectivity.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Network Error Handling',
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  Future<void> checkInternetConnection(BuildContext context) async {
    var connectivityResult = await Connectivity().checkConnectivity();
    if (connectivityResult == ConnectivityResult.none) {
      // Display a "No Internet Connection" message
      showDialog(
        context: context,
        builder: (context) => AlertDialog(
          title: Text('No Internet Connection'),
          content: Text('Please check your internet connection and try again.'),
          actions: [
            TextButton(
              onPressed: () => Navigator.pop(context),
              child: Text('OK'),
            ),
          ],
        ),
      );
    } else {
      // Perform the network request
      // ...
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Network Error Handling')),
      body: Center(
        child: ElevatedButton(
          onPressed: () => checkInternetConnection(context),
          child: Text('Check Internet Connection'),
        ),
      ),
    );
  }
}

In this illustration, the connectivity package is used to examine the status of the internet connection. We show an AlertDialog with a “No Internet Connection” message if the connection is unreliable (ConnectivityResult.none), If an internet connection is accessible, you can execute the network request as necessary.

Example 2: Handling Server Errors:
Let’s now illustrate how to deal with server failures, such 404 Not Found or 500 Internal Server Error, and show users the appropriate error messages.

import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Server Error Handling',
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  Future<void> fetchData() async {
    try {
      // Perform the network request
      final response = await http.get(Uri.parse('https://example.com/api/data'));

      if (response.statusCode == 200) {
        // Handle successful response
        // ...
      } else {
        // Handle server error and display appropriate message
        showDialog(
          context: context,
          builder: (context) => AlertDialog(
            title: Text('Server Error'),
            content: Text('An error occurred while fetching data from the server.'),
            actions: [
              TextButton(
                onPressed: () => Navigator.pop(context),
                child: Text('OK'),
              ),
            ],
          ),
        );
      }
    } catch (e) {
      // Handle other errors, such as network issues
      print('Error: $e');
      showDialog(
        context: context,
        builder: (context) => AlertDialog(
          title: Text('Error'),
          content: Text('An error occurred. Please try again later.'),
          actions: [
            TextButton(
              onPressed: () => Navigator.pop(context),
              child: Text('OK'),
            ),
          ],
        ),
      );
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Server Error Handling')),
      body: Center(
        child: ElevatedButton(
          onPressed: () => fetchData(),
          child: Text('Fetch Data'),
        ),
      ),
    );
  }
}

In this example, we’ll use the http package to send a fictitious API endpoint a network request. If the server sends back a 200 status code for a successful response, we handle the successful data. Instead, we display an AlertDialogthe relevant error message if the server returns an error (status code other than 200).

A general “An error occurred” message will be displayed whenever a network request-related error, such as a network problem, is encountered. Message: “Please try again later.”

8. Reporting and Error Logging

Recording errors, exceptions, and crashes that happen in your program are known as error logging. This data is useful for identifying problems and comprehending how they affect consumers. Error reporting, on the other hand, involves sending error data to a server or cloud platform where it may be analyzed and compiled for developers to evaluate.

Example: Integrating Firebase Crashlytics with Error Logging: We’ll walk you through integrating Firebase Crashlytics to record and report failures in your Flutter app in this example:

1. Create a Firebase project in Flutter:

• To create and include a new Firebase project into your Flutter app using the Firebase SDK, adhere to the official Firebase guide.

2. Crashlytics Firebase plugin addition:

• In your pubspec.yaml file, add the firebase_crashlytics plugin:

dependencies:
  flutter:
    sdk: flutter
  firebase_core: 
  firebase_crashlytics:

3. Initialize Firebase Crashlytics:

• In your app’s entry point (usually main.dart), initialize Firebase Crashlytics:

import 'package:flutter/material.dart';
import 'package:firebase_core/firebase_core.dart';
import 'package:firebase_crashlytics/firebase_crashlytics.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  FirebaseCrashlytics.instance.setCrashlyticsCollectionEnabled(true);
  runApp(MyApp());
}

4. Implement Error Logging:

• Whenever you want to log an error, use FirebaseCrashlytics.instance.recordError():

try {
  // Your code that may throw an exception
} catch (e, stackTrace) {
  // Log the error using Firebase Crashlytics
  FirebaseCrashlytics.instance.recordError(e, stackTrace);
}

5. View Crash Reports:

• Your Firebase console will automatically receive crash reports. Visit the “Crashlytics” section of the Firebase console to see them.

9. Individualised Error Handling Techniques

Custom error handling entails modifying error handling algorithms to address fault circumstances unique to a certain app or to give consumers specialized feedback. This may entail dealing with mistakes that are exclusive to a given domain, displaying unique error panels, or interacting with particular error reporting systems.

Custom error handling for a shopping app, for instance:
Let’s give an example of bespoke error handling for a shopping app, handling cart-related issues and showing customers the proper messages:

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Custom Error Handling',
      home: MyShoppingPage(),
    );
  }
}

class MyShoppingPage extends StatefulWidget {
  @override
  _MyShoppingPageState createState() => _MyShoppingPageState();
}

class _MyShoppingPageState extends State<MyShoppingPage> {
  List<String> cartItems = ['Item A', 'Item B', 'Item C'];

  void addToCart(String item) {
    setState(() {
      cartItems.add(item);
    });
  }

  void removeFromCart(String item) {
    if (!cartItems.contains(item)) {
      // Custom handling for cart item not found
      showDialog(
        context: context,
        builder: (context) => AlertDialog(
          title: Text('Error'),
          content: Text('Item not found in the cart.'),
          actions: [
            TextButton(
              onPressed: () => Navigator.pop(context),
              child: Text('OK'),
            ),
          ],
        ),
      );
    } else {
      setState(() {
        cartItems.remove(item);
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Custom Error Handling')),
      body: ListView.builder(
        itemCount: cartItems.length,
        itemBuilder: (context, index) {
          return ListTile(
            title: Text(cartItems[index]),
            trailing: IconButton(
              icon: Icon(Icons.delete),
              onPressed: () => removeFromCart(cartItems[index]),
            ),
          );
        },
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          // Simulating an error for an item not found in the cart
          removeFromCart('Item D');
        },
        child: Icon(Icons.remove),
      ),
    );
  }
}

In this case, we develop a shopping application that enables users to add and delete goods from their shopping carts. The removeFromCart function now uses a unique error-handling method that we developed ourselves. We show AlertDialog a unique error message (“Item not found in the cart.”) whenever the user attempts to delete an item that is not in the cart.

This retail app’s customized error handling caters to a particular use case that is peculiar to the app’s industry. To improve user experience and handle unique cases, you may build a variety of bespoke error-handling algorithms depending on the needs of your app.

10. Flutter’s Best Practises for Handling Errors

For a Flutter app to be stable, dependable, and to provide a good user experience, error management is essential. You may manage problems in your Flutter apps more effectively by following these recommended practices:

1. User-Friendly Error Messages: Display concise and informative error messages to users when an issue occurs. Keep technical information that people might not comprehend out of sight. Instead, give them useful advice on how to go forward or what they can do to remedy the problem.
2. Try-catch Blocks Should Be Used for Exceptions: Try-catch blocks can be used to capture and gracefully manage exceptions in code that is prone to them. By doing so, you may avoid app crashes and properly handle problems.
3. Futures and Streams are Used to Handle Asynchronous Errors: Pay close attention to how errors are handled while doing asynchronous operations utilizing streams and futures. To properly manage failures, Futures should use .catchError() and Streams should use onError().
4. Implement global error handling: Create techniques for catching errors and unhandled exceptions uniformly across all displays. This guarantees a seamless user experience and helps with problem-solving.
5. Error logging should be used to record: error details for monitoring and troubleshooting reasons. Identify major issues in production by logging and reporting failures using tools like Firebase Crashlytics.
6. Create Custom Error Handling for Particular Situations: Customise error handling to meet the needs of your app. For app-specific failures or circumstances, provide custom error messages and handling logic.
7. Identify network connectivity issues and server problems: gracefully handle network-related issues including network outages or server problems. Users should be made aware of connectivity problems and given pertinent error messages.
8. Graceful Degradation for Feature Unavailability: Handle feature unavailability gently if some features rely on platform-specific functionality or external services. When functionalities are not available due to external circumstances or are not supported by the user’s current platform, users should be notified.
9. Keep Force Crashes Out of Production: While force crashes can be helpful for testing and debugging, keep them out of builds intended for usage in actual production. Force crashes ruin the user experience and could get bad feedback.
10. Test Error circumstances: Make sure your error handling logic functions as intended in a variety of error circumstances by thoroughly testing it. To make sure your app responds politely to failures, test both expected and unexpected ones.

Keep in mind that error management is a continual process and that improving your error-handling techniques based on user feedback and app analytics will enhance your users’ app experiences.

11. Using Unit Tests to Test Error Scenarios

Small, isolated code units, such as functions or methods, are tested for functioning using unit tests. You will develop test cases that replicate various error circumstances and check that the error handling logic reacts appropriately when you write unit tests for error handling.

Example: Unit Testing Error Handling:
Let’s illustrate how to create unit tests using the test package to test various error scenarios and evaluate error-handling behavior:

import 'package:flutter_test/flutter_test.dart';

// Function to test: Division function
double divideNumbers(int numerator, int denominator) {
  if (denominator == 0) {
    throw Exception('Division by zero is not allowed.');
  }
  return numerator / denominator;
}

void main() {
  // Test case 1: Testing successful division
  test('Test successful division', () {
    expect(divideNumbers(10, 2), equals(5));
  });

  // Test case 2: Testing division by zero
  test('Test division by zero', () {
    try {
      divideNumbers(10, 0);
      // The line below should not be reached.
      fail('Expected an exception to be thrown.');
    } catch (e) {
      expect(e, isA<Exception>());
      expect(e.toString(), contains('Division by zero is not allowed.'));
    }
  });

  // Test case 3: Testing division with negative numbers
  test('Test division with negative numbers', () {
    expect(divideNumbers(-10, 2), equals(-5));
  });
}

We have a function called divideNumbers that divides numbers in our case. Three unit tests were created to address various scenarios:

1. Test case 1: Tests a productive division against the anticipated results.
2. Test case 2: Tests the case in which the denominator is 0, which should cause an exception to be thrown along with the necessary error message.
3. Test case 3: Division is tested with negative numbers.

You can verify that the divideNumbers method handles various circumstances appropriately and throws exceptions as intended by running these unit tests.

In order to maintain code quality and make sure your software reacts effectively to various error cases, writing unit tests for error handling is crucial. It also acts as a safety net when you modify your codebase since you can easily spot any errors that arise while developing.

Conclusion

We’ll emphasize the value of strong error handling in Flutter and how it enhances the user experience as we draw to a close. By employing good error-handling techniques and adhering to best practices, you may create dependable and user-friendly Flutter apps.

source:

https://medium.com/@parthbhanderi01/complete-guide-to-flutter-error-handling-techniques-and-code-examples-37414dd0992f

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