implementation project(path:':unityLibrary')
 implementation fileTree(dir: project(':unityLibrary').getProjectDir().toString()+('\\libs'), include: ['*.jar', '*.aar'])

     ndk {
            abiFilters 'armeabi-v7a', 'arm64-v8a'
        }

unityStreamingAssets=.unity3d, google-services-desktop.json, google-services.json, GoogleService-Info.plist

<string name="game_view_content_description">Game view</string>

Button myBtn=  findViewById(R.id.button);

myBtn.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        Intent intent = new Intent(MainActivity.this,UnityPlayerActivity.class);
        startActivity(intent);
    }
});

package com.xingame.unitycallandroid;

import android.os.Bundle;
import android.widget.Toast;

import com.unity3d.player.UnityPlayer;

public class MainActivity extends UnityPlayerActivity {


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //setContentView(R.layout.activity_main);
    }

    //unity調用Android
    public void UnityCallAndroid () {

        Toast.makeText(this,"unity調用android成功", Toast.LENGTH_LONG).show();

        AndroidCallUnity();
    }
    
    //android調用unity
    public void AndroidCallUnity () {

        //第1個參數為Unity場景中用于接收android消息的對象名稱
        //第2個參數為對象上的腳本的一個成員方法名稱（腳本名稱不限制）
        //第3個參數為unity方法的參數
        UnityPlayer.UnitySendMessage("receiveObj", "UnityMethod", "This is args.");
    }

}

  private void OnBtnClickHandler()
    {
        using (jc = new AndroidJavaClass("com.unity3d.player.UnityPlayer")){
            using (jo = jc.GetStatic<AndroidJavaObject>("currentActivity")){
                jo.Call("UnityCallAndroid");
            }
        }
    }