Having trouble figuring out how to place code into kotlin and use a method channel to send functions from flutter - flutter

Question

My MainActivity.kt:
class MainActivity : FlutterActivity() {
private val CHANNEL = "flutter.native/helper"
private var mapId: Int? = null
override fun onCreate(savedInstanceState: Bundle?, PersistentState: PersistableBundle?) {
super.onCreate(savedInstanceState, PersistentState)
GeneratedPluginRegistrant.registerWith(FlutterEngine(this));
}
override fun configureFlutterEngine(#NonNull flutterEngine: FlutterEngine) {
GeneratedPluginRegistrant.registerWith(flutterEngine);
MethodChannel(flutterEngine.dartExecutor, CHANNEL).setMethodCallHandler { call, result ->
if (call.method == "KML") {
result.success(getKMLResource());
} else {
result.notImplemented();
}
}
}
private fun getKMLResource(): Int {
return R.raw.borders;
}
}
I'm trying to insert the below call, but I get a errors every time.
override fun onMethodCall(call: MethodCall, result: Result) {
when (call.method) {
"showToast" -> {
val text = call.argument<String>("text") // hello world
showToast(text)
}
}
}
Errors:
'onMethodCall' overrides nothing
One type argument expected for class Result<out T>
Unresolved reference: showToast
Here's my flutter portion:
Future<void> printSomething(GoogleMapController mapController) async {
const MethodChannel channel = MethodChannel('flutter.native/helper');
channel.invokeMethod('showToast', {'text': 'hello world'});
}
I have no idea how to incorporate this into my kotlin code properly, and there aren't many examples out there. At least none that I could find. My ultimate goal is to be able to manipulate private fun getKMLResource() and set return as a directory I select from my flutter app.
Anybody know how to do this? Please help. Thank you.
Here's my add kml flutter function:
Here's how I select my .kml:
Future<void> addKml(GoogleMapController mapController) async {
const MethodChannel channel = MethodChannel('flutter.native/helper');
try {
int kmlResourceId = await channel.invokeMethod('KML');
return mapController.channel.invokeMethod("map#addKML", <String, dynamic>{
'resourceId': kmlResourceId,
});
} on PlatformException catch (e) {
throw 'Unable to plot map: ${e.message}';
}
}

Answer 1

First of all, you gotta follow these documentations:
Writing custom platform-specific code
Supporting the new Android plugins APIs
Error:
'onMethodCall' overrides nothing
Means that you are trying override something that does not exist
In this situation, you have to implement missing classes that are found in the docs tutorial:
ActivityAware, FlutterPlugin, MethodChannel.MethodCallHandler
On:
MethodChannel.MethodCallHandler
You can override (Kotlin snippet):
override fun onMethodCall(call: MethodCall, result: MethodChannel.Result)
That should fix your problem.
ActivityAware and FlutterPlugin are essentials for the new flutter upgrades and you can efficiently fix memory leaks with them.
class BubbleOverlayPlugin : ActivityAware, FlutterPlugin, MethodChannel.MethodCallHandler {
private var activity: Activity? = null
private var channel: MethodChannel? = null
override fun onMethodCall(call: MethodCall, result: MethodChannel.Result) {
when (call.method) {
//here lies the platform methods calls
}
}
override fun onDetachedFromEngine(binding: FlutterPlugin.FlutterPluginBinding) {
channel?.setMethodCallHandler(null)
//release resources
}
override fun onAttachedToEngine(#NonNull flutterPluginBinding: FlutterPlugin.FlutterPluginBinding) {
channel = MethodChannel(flutterPluginBinding.binaryMessenger, channelName)
channel?.setMethodCallHandler(this)
}
override fun onAttachedToActivity(binding: ActivityPluginBinding) {
activity = binding.activity
}
override fun onDetachedFromActivity() {
//release resources
}
override fun onReattachedToActivityForConfigChanges(binding: ActivityPluginBinding) {
activity = binding.activity
}
override fun onDetachedFromActivityForConfigChanges() {
//release resources
}
}
You can check my source code from the plugin bubble_overlay, It is using the last docs recommendations.
Repo: bubble_overlay repo