Android同意我们使用Service组件来完毕后台任务。这些任务的同意不会影响到用户其它的交互。

 

1、Activity类

 package demo.camera;
 import android.app.Activity;
 import android.content.ComponentName;
 import android.content.Context;
 import android.content.Intent;
 import android.content.ServiceConnection;
 import android.os.Bundle;
 import android.os.IBinder;
 import android.view.View;
 /**
  * 演示Activity怎样利用Service来完毕后台Audio的播放功能
  * 同一时候怎样将Service和Activity进行绑定
  * @author Administrator
  *
  */
 public class BackgroundAudioDemo extends Activity {

     private AudioService audioService;

     //使用ServiceConnection来监听Service状态的变化
     private ServiceConnection conn = new ServiceConnection() {

         @Override
         public void onServiceDisconnected(ComponentName name) {
             // TODO Auto-generated method stub
             audioService = null;
         }

         @Override
         public void onServiceConnected(ComponentName name, IBinder binder) {
             //这里我们实例化audioService,通过binder来实现
             audioService = ((AudioService.AudioBinder)binder).getService();

         }
     };

     public void onCreate(Bundle savedInstanceState){
         super.onCreate(savedInstanceState);
         setContentView(R.layout.back_audio);
     }


     public void onClick(View v){
         int id = v.getId();
         Intent intent = new Intent();
         intent.setClass(this, AudioService.class);
         if(id == R.id.btn_start){
             //启动Service。然后绑定该Service，这样我们能够在同一时候销毁该Activity，看看歌曲是否还在播放
             startService(intent);
             bindService(intent, conn, Context.BIND_AUTO_CREATE);
             finish();
         }else if(id == R.id.btn_end){
             //结束Service
             unbindService(conn);
             stopService(intent);
             finish();
         }else if(id == R.id.btn_fun){
             audioService.haveFun();
         }
     }
 }

2、Service类

 package demo.camera;
 import android.app.Service;
 import android.content.Intent;
 import android.media.MediaPlayer;
 import android.os.Binder;
 import android.os.IBinder;
 import android.widget.MediaController.MediaPlayerControl;
 /**
  * 为了能够使得在后台播放音乐，我们须要Service
  * Service就是用来在后台完毕一些不须要和用户交互的动作
  * @author Administrator
  *
  */
 public class AudioService extends Service implements MediaPlayer.OnCompletionListener{

     MediaPlayer player;

     private final IBinder binder = new AudioBinder();
     @Override
     public IBinder onBind(Intent arg0) {
         // TODO Auto-generated method stub
         return binder;
     }
     /**
      * 当Audio播放完的时候触发该动作
      */
     @Override
     public void onCompletion(MediaPlayer player) {
         // TODO Auto-generated method stub
         stopSelf();//结束了。则结束Service
     }

     //在这里我们须要实例化MediaPlayer对象
     public void onCreate(){
         super.onCreate();
         //我们从raw目录中获取一个应用自带的mp3文件
         player = MediaPlayer.create(this, R.raw.tt);
         player.setOnCompletionListener(this);
     }

     /**
      * 该方法在SDK2.0才開始有的。替代原来的onStart方法
      */
     public int onStartCommand(Intent intent, int flags, int startId){
         if(!player.isPlaying()){
             player.start();
         }
         return START_STICKY;
     }

     public void onDestroy(){
         //super.onDestroy();
         if(player.isPlaying()){
             player.stop();
         }
         player.release();
     }

     //为了和Activity交互，我们须要定义一个Binder对象
     class AudioBinder extends Binder{

         //返回Service对象
         AudioService getService(){
             return AudioService.this;
         }
     }

     //后退播放进度
     public void haveFun(){
         if(player.isPlaying() && player.getCurrentPosition()>2500){
             player.seekTo(player.getCurrentPosition()-2500);
         }
     }
 }

3、在清单文件AndroidManifest.xml中配置Service

 

        <service 

            android:name=".AudioService" />