AndroidStudio实现音乐播放器

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package com.example.myapplication;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;

import android.Manifest;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

 private Button btnStop;
 private boolean isCast; //是否为广播激活

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  if (ContextCompat.checkSelfPermission(this, Manifest.permission.RECEIVE_SMS) != PackageManager.PERMISSION_GRANTED){
   ActivityCompat.requestPermissions(this,new String[]{"android.permission.RECEIVE_SMS"},1);
  }
  btnStop=findViewById(R.id.btnStop);
  Intent intent = getIntent(); //获取广播意图对象
  isCast = intent.getBooleanExtra("iscast", false); //默认值为false
  btnStop.setEnabled(isCast); //设置停止按钮可用和单击监听
  if(isCast) Toast.makeText(this, "正在播放音乐...", Toast.LENGTH_SHORT).show();
  btnStop.setOnClickListener(new View.OnClickListener() {
   @Override
   public void onClick(View v){
    //显式服务调用意图（非绑定式）
    Intent intent=new Intent(MainActivity.this, MyAudioService.class);
    //在Activity组件里，停止音乐播放服务
    stopService(intent);
    isCast=false;
    btnStop.setEnabled(isCast);
//    finish(); //销毁本活动
   }
  });
 }
 @Override
 public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
  super.onRequestPermissionsResult(requestCode, permissions, grantResults);
  switch (requestCode){
   case 1:
    if(grantResults[0]!=PackageManager.PERMISSION_GRANTED){
     Toast.makeText(this, "未授权，无法实现预定的功能！", Toast.LENGTH_SHORT).show();
     finish();
    }else{
     Toast.makeText(this, "请发一条短信验证...", Toast.LENGTH_SHORT).show();
    }
  }
 }
}

package com.example.myapplication;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;

/*
 本广播接收者程序分别调用了应用的主Activity程序和播放音乐的服务程序
*/
public class SmsReceiver extends BroadcastReceiver {
 @Override
 public void onReceive(Context context, Intent intent) {

  Intent serviceIntent = new Intent(context, MyAudioService.class);
  //在广播组件里，通过上下文对象启动音乐播放服务组件
  context.startService(serviceIntent);

  //新建调用Activity组件的意图
  Intent activityIntent = new Intent(context, MainActivity.class);
  activityIntent.putExtra("iscast", true); //携带数据
  //新建栈用来存放被启动的Activity（当已经存在时，只做移动处理）
  activityIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
  //在广播组件里，通过上下文对象启动Activity组件
  context.startActivity(activityIntent);
 }
}

package com.example.myapplication;

import android.app.Service;
import android.content.Intent;
import android.media.MediaPlayer;
import android.os.IBinder;


public class MyAudioService extends Service {
 MediaPlayer mediaPlayer;

 @Override
 public IBinder onBind(Intent intent) {
  return null;
 }
 @Override
 public void onCreate() {
  mediaPlayer = MediaPlayer.create(this, R.raw.liyue);//创建音乐服务。播放R.raw中的音乐liyue
  mediaPlayer.start();//开始服务
 }
 @Override
 public void onDestroy() {
  mediaPlayer.stop();
 }
}