Flutter Module in Android App

Today I’m going to import a Flutter module into an existing Android app. Moreover, I’ll call native methods from that Flutter screen. Because I solved the issue which I mentioned in the last paragraph of my previous story, thanks to Muhannad Fakhouri.

I created a basic Android app and imported a Flutter module. By the FloatingActionButton, I’m starting the FlutterActivity with a route and put a parameter for the title to handle on the Dart side.

FloatingActionButton fab = findViewById(R.id.fab);

fab.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        startActivity(
              new FlutterActivity
                    .NewEngineIntentBuilder(MyFlutterActivity.class)
                    .initialRoute("/second")
                    .build(getApplicationContext())
                    .putExtra("title", "Title")

        );
    }
});

I located MyFlutterActivity.java on the same folder as other java classes and defined the activity in Manifest.xml.

<activity android:name=".MyFlutterActivity"
    android:theme="@style/AppTheme"
    android:configChanges="orientation|keyboardHidden|keyboard|screenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"
    android:hardwareAccelerated="true"
    android:windowSoftInputMode="adjustResize"
    />

Then, I override the onCreate method of MyFlutterActivity to get the title parameter and set it to a global variable:

String title = "";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    Bundle extras = getIntent().getExtras();
    title = extras.getString("title");
}

And override the configureFlutterEngine to handle the method calls from the Dart side of the app.

@Override
public void configureFlutterEngine(@NonNull FlutterEngine flutterEngine) {
    GeneratedPluginRegistrant.registerWith(flutterEngine);

    new MethodChannel(flutterEngine.getDartExecutor().getBinaryMessenger(), CHANNEL).setMethodCallHandler(((methodCall, result) -> {
        if (methodCall.method.equals("getBatteryLevel")) {
            result.success("batteryLevel"); 
        } else if (methodCall.method.equals("getTitle")) {
            result.success(title); // It returns "Title".
        } else {
            result.notImplemented();
        }
    }));
}

Now, I can easily call the related invokeMethod in the initState of SecondScreen.dart to get the title that passed as an argument from the native side.

@override
void initState() {
  super.initState();

  getTitle();
}

getTitle() async {
    String res = await platformMethodChannel.invokeMethod('getTitle');

    setState(() {
      title = res;
    });
}

Voila! The parameter “Title” is on the screen.

And I can invoke the other methods like getBatteryLevel in this Flutter screen.

void _incrementCounter() async {
  try {
    String response =
        await platformMethodChannel.invokeMethod('getBatteryLevel');

    print(response);
    setState(() {
      title = response;
    });
  } on PlatformException catch (e) {
    print("e.message");
    print(e.message);
  }

  setState(() {
    _counter++;
  });
}

The parameter has changed as demonstrated below.

You can access the GitHub repo about this story from here:

deremakif/FlutterModuleSample