一:在AndroidManifest.xml添加

<meta-data
            android:name="flutterEmbedding"
            android:value="2" />

截屏2021-08-11 上午8.35.07.png

二.在MainActivity.kt中

(1)替换引用

//1.删除引用
import io.flutter.app.FlutterActivity
import io.flutter.plugin.common.MethodChannel.MethodCallHandler
import io.flutter.plugin.common.MethodChannel.Result

//2.添加引用
import androidx.annotation.NonNull
import io.flutter.embedding.android.FlutterActivity
import io.flutter.embedding.engine.FlutterEngine
import io.flutter.plugin.common.MethodChannel
import io.flutter.plugins.GeneratedPluginRegistrant

(2)替换入口

//1.删除方法onCreate
class MainActivity : FlutterActivity() {
//入口
 override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
       //以前写代码的地方...
    }
}

//2.添加方法configureFlutterEngine
class MainActivity : FlutterActivity() { 
//入口
override fun configureFlutterEngine(flutterEngine: FlutterEngine)  {
      // super.configureFlutterEngine(flutterEngine)
       //现在写代码的地方...
    }
}

//3.注意 
//如果MainActivity继承的不是FlutterActivity,需要添加下面的代码
//如果MainActivity继承的是FlutterActivity,不需要添加下面的代码
//super.configureFlutterEngine(flutterEngine)

(3)替换信道

//定义的信道的名
  private static final String CHANNEL = "samples.flutter.channel.name";

//1.删除
      new MethodChannel(getFlutterView(), CHANNEL).setMethodCallHandler(
              new MethodCallHandler() {
                   @Override
                   public void onMethodCall(MethodCall call, Result result) {
                       // 以前的接收flutter端信息的代码...
               }
           });

//2添加
new MethodChannel(flutterEngine.getDartExecutor().getBinaryMessenger(), CHANNEL)
               .setMethodCallHandler(
                   (call, result) -> {
                     // 现在的接收flutter端信息的代码...
              }
       );

(4)替换GeneratedPluginRegistrant类的引用

//1.删除引用
package io.flutter.plugins;
import io.flutter.plugin.common.PluginRegistry;
import io.flutter.plugins.connectivity.ConnectivityPlugin;
import com.flutter_webview_plugin.FlutterWebviewPlugin;
import com.foxconn.imes_base_plugins.ImesBasePluginsPlugin;
import com.github.sososdk.orientation.OrientationPlugin;
import io.flutter.plugins.pathprovider.PathProviderPlugin;
import io.flutter.plugins.sharedpreferences.SharedPreferencesPlugin;

//2.添加引用
package io.flutter.plugins;
import androidx.annotation.Keep;
import androidx.annotation.NonNull;
import io.flutter.embedding.engine.FlutterEngine;
import io.flutter.embedding.engine.plugins.shim.ShimPluginRegistry;

//3清理残存
flutter clean

//4.重装插件
flutter pub get

(5)重启项目

三:参考

(1)flutter官网参考:
https://github.com/flutter/flutter/wiki/Upgrading-pre-1.12-Android-projects

(2)flutter代码参考:
https://www.jianshu.com/p/9c1e14fc16ec
https://blog.csdn.net/csdnnews/article/details/114715014