I’m Stuck! I am Unable to Use Native Code in My Flutter Application After the App Has Been Killed

Oh no! You’ve worked tirelessly to create a fantastic Flutter app, only to realize that your native code isn’t working as expected after the app has been killed. Don’t worry, friend, you’re not alone! This frustrating issue has puzzled many a Flutter developer, but fear not, for we’re about to dive into the solution together.

Understanding the Problem

Before we dive into the fix, let’s quickly understand what’s causing the issue. When your app is killed, the platform (Android or iOS) terminates the process, and all resources are released. When you restart the app, a new instance is created, and your native code, which relies on the previous instance, is no longer valid.

The Native Code Conundrum

In Flutter, native code is executed using platform channels, which allow your Dart code to communicate with native code on the underlying platform. When the app is killed, the platform channel is destroyed, and your native code is no longer accessible.

The Solution: Relaunching the Native Code

So, how do we overcome this hurdle? The answer lies in relaunching the native code after the app has been killed. Here’s a step-by-step guide to help you achieve this:

Step 1: Handle App Lifecycle Events

In Flutter, you can use the WidgetsBinding class to listen to app lifecycle events, such as when the app is paused or resumed. You’ll need to add the following code to your app:

import 'package:flutter/widgets.dart';

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> with WidgetsBindingObserver {
  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addObserver(this);
  }

  @override
  void dispose() {
    WidgetsBinding.instance.removeObserver(this);
    super.dispose();
  }

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    if (state == AppLifecycleState.paused) {
      // App is being killed, save native code state
      _saveNativeCodeState();
    } else if (state == AppLifecycleState.resumed) {
      // App is being relaunched, restore native code state
      _restoreNativeCodeState();
    }
  }
}

Step 2: Save Native Code State

In the didChangeAppLifecycleState method, when the app is paused (killed), you’ll need to save the native code state. This can be done using a platform channel to invoke a native method that saves the required data.

Future<void> _saveNativeCodeState() async {
  final platform = MethodChannel('com.example/native_code_channel');
  await platform.invokeMethod('saveNativeCodeState');
}

Step 3: Restore Native Code State

When the app is resumed (relaunched), you’ll need to restore the native code state. Again, use a platform channel to invoke a native method that restores the saved data.

Future<void> _restoreNativeCodeState() async {
  final platform = MethodChannel('com.example/native_code_channel');
  await platform.invokeMethod('restoreNativeCodeState');
}

Native Code Implementation

On the native side, you’ll need to implement the saveNativeCodeState and restoreNativeCodeState methods.

Android (Java)

public class NativeCodeChannel {
  public void saveNativeCodeState() {
    // Save native code state to SharedPreferences or a file
  }

  public void restoreNativeCodeState() {
    // Restore native code state from SharedPreferences or a file
  }
}

iOS (Swift)

@objc(NativeCodeChannel)
class NativeCodeChannel: NSObject {
  @objc func saveNativeCodeState() {
    // Save native code state to UserDefaults or a file
  }

  @objc func restoreNativeCodeState() {
    // Restore native code state from UserDefaults or a file
  }
}

Bonus: Additional Tips and Considerations

While the above solution should get your native code working again, here are some additional tips and considerations to keep in mind:

• Handle Native Code Errors**: Make sure to handle errors that occur when saving or restoring native code state. This can include errors while writing to or reading from storage.
• Optimize Native Code State**: Only save the necessary data to minimize storage usage and optimize performance.
• Use Secure Storage**: When saving sensitive data, use secure storage options like SharedPreferences on Android or Keychain on iOS.

Conclusion

And there you have it! By following these steps, you should be able to overcome the hurdle of using native code in your Flutter application after the app has been killed. Remember to handle app lifecycle events, save and restore native code state, and implement the necessary native code logic on both Android and iOS. With these tips and considerations in mind, you’ll be well on your way to creating a seamless and robust Flutter app.

Issue	Solution
I am unable to use native code in my Flutter application after the app has been killed	Handle app lifecycle events, save and restore native code state, and implement native code logic on Android and iOS

By following this comprehensive guide, you’ll be able to overcome this frustrating issue and provide a better user experience for your app users. Happy coding!

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