Android开发之音乐播放器的实现

Android音乐播放器

使用到Android的Actiivity和Service组件

播放音频的代码应该运行在服务中，定义一个播放服务MusicService，服务里定义play、stop、pause、continuePlay等方法

把这几个方法抽取成一个接口MusicInterface

定义一个中间人类，继承Binder，实现MusicInterface

操作按钮等使用Activity与用户交互

同时为了把服务所在进程变成服务进程，防止Activity销毁时依旧执行Service，需要使用Service启动的混合调用，即先使用startService()，然后使用bindService()方法。

原理：使用bindService()方法，启动service。在ServiceConnection的onServiceConnected()方法中返回一个iBinder对象，通过该对象可以操作音乐service中的播放音乐的方法。

播放服务

代码：

MainActivity:

 import android.app.Activity;
 import android.content.ComponentName;
 import android.content.Intent;
 import android.content.ServiceConnection;
 import android.os.Bundle;
 import android.os.Handler;
 import android.os.IBinder;
 import android.view.View;
 import android.widget.SeekBar;
 import android.widget.SeekBar.OnSeekBarChangeListener;

 public class MainActivity extends Activity {

     private MusicInterface mi;

     static Handler handler = new Handler() {
         public void handleMessage(android.os.Message msg) {
             Bundle bundle = msg.getData();
             //取出消息携带的数据
             int duration = bundle.getInt("duration");
             int currentPosition = bundle.getInt("currentPosition");
             //刷新播放进度
             sb.setMax(duration);
             sb.setProgress(currentPosition);
         };
     };

     private static SeekBar sb;
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
         sb = (SeekBar) findViewById(R.id.sb);
         //给sb设置一个拖动侦听
         sb.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {
             //停止拖动时调用
             @Override
             public void onStopTrackingTouch(SeekBar seekBar) {
                 //根据拖动进度，改变音乐播放进度
                 mi.seekTo(seekBar.getProgress());
             }
             //开始拖动时调用
             @Override
             public void onStartTrackingTouch(SeekBar seekBar) {
                 // TODO Auto-generated method stub

             }
             //拖动的时候不断调用
             @Override
             public void onProgressChanged(SeekBar seekBar, int progress,
                     boolean fromUser) {
                 // TODO Auto-generated method stub

             }
         });
         Intent intent = new Intent(this, MusicService.class);
         //先start启动MusicService，再bind
         startService(intent);
         MyServiceConn conn = new MyServiceConn();
         bindService(intent, conn, BIND_AUTO_CREATE);
     }

     class MyServiceConn implements ServiceConnection {

         @Override
         public void onServiceConnected(ComponentName name, IBinder service) {
             mi = (MusicInterface) service;
         }

         @Override
         public void onServiceDisconnected(ComponentName name) {

         }

     }

     public void play(View v) {
         mi.play();
     }

     public void continuePlay(View v) {
         mi.continuePlay();
     }

     public void pause(View v) {
         mi.pause();
     }

     public void stop(View v) {
         mi.stop();
     }
 }

MusicService:

 import java.util.Timer;
 import java.util.TimerTask;

 import android.app.Service;
 import android.content.Intent;
 import android.media.MediaPlayer;
 import android.media.MediaPlayer.OnPreparedListener;
 import android.os.Binder;
 import android.os.Bundle;
 import android.os.IBinder;
 import android.os.Message;

 public class MusicService extends Service {
     private MediaPlayer player;
     private Timer timer;

     @Override
     public IBinder onBind(Intent intent) {
         // TODO Auto-generated method stub
         return new MusicMiddleMan();
     }

     class MusicMiddleMan extends Binder implements MusicInterface {
         public void play() {
             MusicService.this.play();
         }

         public void pause() {
             MusicService.this.pause();
         }

         public void continuePlay() {
             MusicService.this.continuePlay();
         }

         public void stop() {
             MusicService.this.stop();
         }

         @Override
         public void seekTo(int progress) {
             // TODO Auto-generated method stub
             MusicService.this.seekTo(progress);
         }

     }

     @Override
     public void onCreate() {
         // TODO Auto-generated method stub
         super.onCreate();
         player = new MediaPlayer();

     }

     public void play() {
         System.out.println("播放");
         if (player == null) {
             player = new MediaPlayer();
         }
         player.reset();
         try {
                //设置网络资源
             player.setDataSource("http://192.168.5.100:8080/HEYJUDE.mp3");
             // 异步获取网络资源
             player.prepareAsync();
             player.setOnPreparedListener(new OnPreparedListener() {

                 @Override
                 public void onPrepared(MediaPlayer mp) {
                     player.start();
                     addTimer();

                 }
             });
         } catch (Exception e) {
             e.printStackTrace();
         }

     }

     public void continuePlay() {
         System.out.println("继续播放");
         player.start();
     }

     public void pause() {
         System.out.println("暂停");
         player.pause();
     }

     public void stop() {
         System.out.println("停止");
         player.stop();
         player.release();
         player = null;
         if (timer!=null) {
             timer.cancel();
             timer=null;
         }
     }

     public void seekTo(int progress){
         player.seekTo(progress);
     }

     public void addTimer() {
         //播放进度需要不停的获取，不停的刷新进度条，使用计时器每1000毫秒获取一次播放进度
         //发消息至Handler，把播放进度放进Message对象中，在Handler中更新SeekBar的进度
         if (timer == null) {

             timer = new Timer();
             timer.schedule(new TimerTask() {

                 @Override
                 public void run() {
                     // 获取到歌曲总时长
                     int duration = player.getDuration();
                     // 获取歌曲当前进度
                     int currentPosition = player.getCurrentPosition();
                     Message msg = MainActivity.handler.obtainMessage();
                     Bundle bundle = new Bundle();
                     bundle.putInt("duration", duration);
                     bundle.putInt("currentPosition", currentPosition);
                     msg.setData(bundle);
                     MainActivity.handler.sendMessage(msg);

                 }
             }, 5, 1000);
         }

     }

 }

把MusicControl类抽取出来为接口，这样可以在MainActivity中只可以访问接口的方法，MusicControl类中的其他方法不被方法

MusicInterface:

 public interface MusicInterface {

     void play();
     void continuePlay();
     void stop();
     void pause();
     void seekTo(int progress);

 }