How do I pass an Activity via MethodChannel in Flutter? - flutter

Question

I'm making a Flutter app that needs to call a third party library (jar file provided).
The Java documentation for the third-party API object is created by calling something
public class MainActivity extends Activity {
private ThirdPartyAPI mAPI;
private ThirdPartyAPICallbacks mCallbacks = new ThirdPartyAPICallbacks(){
#Override
public void Connected() {
}
};
protected void onCreate(Bundle savedInstanceState) {
mAPI = new ThirdPartyAPI(this, mCallbacks); // how do we do the equivalent in Flutter?
}
}
How do I do this in Flutter?
I tried MethodChannel, but I don't know what to pass as the Activity instance to the ThirdPartyAPI constructor.

Answer 1

MethodChannel doesn't and will never allow to send something like an Activity.
The only types allowed are the following from the official DOCS:
If you really need to send something to Flutter, you'd need to create a method on Flutter which will call Java/Kotlin side, then get anything important you need from that 3rd party API/Library/Etc and send that info back to Flutter using a MethodChannel.

Answer 2

You don't transfer to Activity across the method channel. It only ever exists at the Java end. Instead it gets 'attached' to the Java end of the channel.
When creating a plugin (this is probably preferred as you can re-use it in different projects), make sure the plugin class also implements ActivityAware. Create stub implementation for the four methods required, in particular onAttachedToActivity.
For example:
public class ThirdPartyApiPlugin implements FlutterPlugin, ActivityAware {
#Override
public void onAttachedToActivity(ActivityPluginBinding binding) {
Activity activity = binding.getActivity();
mAPI = new ThirdPartyAPI(activity, mCallbacks);
}
If not using a plugin, modify the MainActivity class as described here.
public class MainActivity extends FlutterActivity {
private static final String CHANNEL = "someChannelName";
#Override
public void configureFlutterEngine(#NonNull FlutterEngine flutterEngine) {
GeneratedPluginRegistrant.registerWith(flutterEngine);
mAPI = new ThirdPartyAPI(this, mCallbacks);
new MethodChannel(flutterEngine.getDartExecutor().getBinaryMessenger(), CHANNEL)
.setMethodCallHandler(
(call, result) -> {
// Note: this method is invoked on the main thread.
// TODO
}
);
}
}