Type mismatch: inferred type is MainActivity but FlutterEngine was expected

Question

I am new on flutter and I want change wallpaper of the device but that needs Method calls from platform channel https://developer.android.com/reference/android/Manifest.permission?hl=en#SET_WALLPAPER and native android wallpaperManager

under the android folder /MainActivity.kt Kotlin file throws an error.

I tried these below:

• A new fresh project with MainActivity.java file
• flutter clean
• flutter pub cache repair

I read about other type mismatch error questions from here but unfortunately not found anything.

Any help appriciated. My code is as below.

MainActivity.kt

    package com.combasis.wallpaper_son_app
import android.os.Bundle
import io.flutter.app.FlutterActivity
import io.flutter.plugin.common.MethodChannel
import io.flutter.plugins.GeneratedPluginRegistrant
import java.io.IOException
import android.app.WallpaperManager
import android.graphics.BitmapFactory
import java.io.File
import android.os.Build
import android.annotation.TargetApi
import android.content.Context
import io.flutter.Log
private const val CHANNEL = "com.combasis.wallpaper_son_app"
class MainActivity: FlutterActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        GeneratedPluginRegistrant.registerWith(this)
    MethodChannel(flutterView, CHANNEL).setMethodCallHandler { call, result ->
        if (call.method == "setWallpaper") {
            val arguments = call.arguments as ArrayList<*>
            val setWallpaper = setWallpaper(arguments[0] as String, applicationContext, arguments[1] as Int)
            if (setWallpaper == 0) {
                result.success(setWallpaper)
            } else {
                result.error("UNAVAILABLE", "", null)
            }
        } else {
            result.notImplemented()
        }
    }
}
@TargetApi(Build.VERSION_CODES.ECLAIR)
private fun setWallpaper(path: String, applicationContext: Context, wallpaperType: Int): Int {
    var setWallpaper = 1
    val bitmap = BitmapFactory.decodeFile(path)
    val wm: WallpaperManager? = WallpaperManager.getInstance(applicationContext)
    setWallpaper = try {
        wm?.setBitmap(bitmap, null, true, wallpaperType)
        0
    } catch (e: IOException) {
        1
    }
    return setWallpaper
}
}

main.dart:...

  static const platform = const MethodChannel('com.combasis.wallpaper_son_app');
  Future<void> _setWallpaper(int wallpaperType, String url) async {
    var file =
    await DefaultCacheManager().getSingleFile(url);
    try {
      final int result = await platform
          .invokeMethod('setWallpaper', [file.path, wallpaperType]);
      print('Wallpaper Updated.... $result');
    } on PlatformException catch (e) {
      print("Failed to Set Wallpaper: '${e.message}'.");
    }
  }

Run:

 Launching lib/main.dart on AOSP on IA Emulator in debug mode...
Running Gradle task 'assembleDebug'...
e: /Users/username/AndroidStudioProjects/walpaperz_app/wallpaper_son_app/android/app/src/main/kotlin/com/combasis/wallpaper_son_app/MainActivity.kt: (21, 48): Type mismatch: inferred type is MainActivity but FlutterEngine was expected
FAILURE: Build failed with an exception.
* What went wrong:
Execution failed for task ':app:compileDebugKotlin'.
> Compilation error. See log for more details
* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.
* Get more help at https://help.gradle.org
BUILD FAILED in 13s
Exception: Gradle task assembleDebug failed with exit code 1

-Android Studio version: 4.0.1

-Kotlin version: 1.3.72-release-Studio4.0-5 stable

-Flutter version: 1.17.2 stable

Solution 1

Please remove GeneratedPluginRegistrant.registerWith(flutterEngine); from MainActivity.kt and update as follows.

import io.flutter.embedding.android.FlutterActivity
class MainActivity: FlutterActivity() {
}

Solution 2

To pass flutter Engine value we can use provideFlutterEngine method. And for flutterView we can use flutterEngine.dartExecutor. Below is the code snippet.

class MainActivity: FlutterActivity() {
private val CHANNEL = "com.startActivity/testChannel"
override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    provideFlutterEngine(this)?.let { GeneratedPluginRegistrant.registerWith(it) }
    MethodChannel(flutterEngine?.dartExecutor,CHANNEL).setMethodCallHandler{ call, result ->
        if(call.method.equals("StartSecondActivity")){
            val intent= Intent(this,KotlinActivity::class.java)
            startActivity(intent)
            result.success("ActivityStarted")
        }
        else{
            result.notImplemented()
        }
    }
}}

Comments

[Ihsan ALGUL]

Thanks for your reply, I tried but result failed same as the mention above.