将现有的 Flutter Kotlin 项目转换为 Flutter Java 项目

我也有同样的问题，对我来说，这个解决方案是有效的.

1. Move folder com.example.test_app (any name you have) from android/app/src/main/kotlin -> android/app/src/main/java

2. 替换主活动.kt的Java版本，或者复制到这里

   package com.example.test_app;
   
   import androidx.annotation.NonNull;
   import io.flutter.embedding.android.FlutterActivity;
   import io.flutter.embedding.engine.FlutterEngine;
   import io.flutter.plugins.GeneratedPluginRegistrant;
   
   public class MainActivity extends FlutterActivity {
    @Override
    public void configureFlutterEngine(@NonNull FlutterEngine flutterEngine) {
    GeneratedPluginRegistrant.registerWith(flutterEngine);
    }
   }
   

3. 删除以下代码android/app/build.grale

   ...
   apply plugin: 'kotlin-android'
   ...
   sourceSets {
       main.java.srcDirs += 'src/main/kotlin'
   }
   

4. 在相同位置替换以下内容:

   dependencies {
       implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
       testImplementation 'junit:junit:4.12'
       androidTestImplementation 'androidx.test:runner:1.1.0'
       androidTestImplementation 'androidx.test.espresso:espresso-core:3.1.0'
   }
   

   至

   dependencies {
       testImplementation 'junit:junit:4.12'
       androidTestImplementation 'com.android.support.test:runner:1.0.2'
       androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
   }