android 使用 service 实现音乐

今天的球员趁service。播放音乐service结束，进度条activity结束，因此，基础工作activity和service互动，本文将使用IBinder互动。主要activity能够调用service的函数。能够參考我的这篇博客。

本文关键点：利用利用IBinder实现activity 控制service

实现功能：

1 控制播放进度：

activity调用service的函数，对MediaPlayer进行控制。

包含启动时的播放和滑动seekbar时。对MediaPlayer进行设置，达到控制播放进度的控制。

2 播放进度更新：

在activity开启多线程。后台每隔100ms就发送一次message，在UI线程中利用handler对message进行判定，之后activity调用service的函数。得到播放的进度（百分比），及时更新seekbar的进度条。

效果图例如以下：

布局非常easy，例如以下所看到的：

<?xml version="1.0" encoding="utf-8"?

>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

	<TextView
	    android:layout_width="wrap_content"
    	android:layout_height="wrap_content"
	    android:text="play"/>    

	<Button
	    android:id="@+id/playButton"
	    android:layout_width="wrap_content"
	    android:layout_height="wrap_content"
	    android:text="play"
	 />

	<Button
	    android:id="@+id/pauseButton"
	    android:layout_width="wrap_content"
	    android:layout_height="wrap_content"
	    android:text="pause"
	 />

	 <SeekBar
        android:id="@+id/seekbar"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_marginLeft="20dp"
        android:layout_marginRight="20dp"
        android:max="100"
        android:progress="10"
        />

</LinearLayout>

activity的代码例如以下：

<pre name="code" class="java">public class MainActivity extends Activity {

	Boolean mBound = false;

	MusicService mService;

	SeekBar seekBar;

	//多线程，后台更新UI
	Thread myThread;

	//控制后台线程退出
	boolean playStatus = true;

	//处理进度条更新
	Handler mHandler = new Handler(){
		@Override
        public void handleMessage(Message msg){
			switch (msg.what){
				case 0:
					//从bundle中获取进度。是double类型，播放的百分比
					double progress = msg.getData().getDouble("progress");

					//依据播放百分比，计算seekbar的实际位置
		            int max = seekBar.getMax();
		            int position = (int) (max*progress);

		            //设置seekbar的实际位置
		            seekBar.setProgress(position);
		            break;
		        default:
		        	break;
			}

        }
	};

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

		//定义一个新线程。用来发送消息。通知更新UI
		myThread = new Thread(new MyThread());

		//绑定service;
		Intent serviceIntent = new Intent(this , MusicService.class);

		//假设未绑定，则进行绑定
		if(!mBound){
			bindService(serviceIntent, mConnection, Context.BIND_AUTO_CREATE);
		}

		//初始化播放button
		Button playButton = (Button)findViewById(R.id.playButton);
		playButton.setOnClickListener(new OnClickListener(){

			@Override
			public void onClick(View arg0) {
				// TODO Auto-generated method stub
				if(mBound){
					mService.play();
				}
			}

		});

		//初始化暂停button
		Button pauseButton = (Button)findViewById(R.id.pauseButton);
		pauseButton.setOnClickListener(new OnClickListener(){
			@Override
			public void onClick(View arg0) {
				// TODO Auto-generated method stub
				//首先须要判定绑定情况
				if(mBound){
					mService.pause();
				}
			}
		});

	    seekBar = (SeekBar)findViewById(R.id.seekbar);
		seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {

			@Override
			public void onStopTrackingTouch(SeekBar seekBar) {
			//手动调节进度
				// TODO Auto-generated method stub
				//seekbar的拖动位置
				int dest = seekBar.getProgress();
				//seekbar的最大值
				int max = seekBar.getMax();
				//调用service调节播放进度
				mService.setProgress(max, dest);
			}

			@Override
			public void onProgressChanged(SeekBar arg0, int arg1, boolean arg2) {
				// TODO Auto-generated method stub

			}

			@Override
			public void onStartTrackingTouch(SeekBar arg0) {
				// TODO Auto-generated method stub

			}

		});		

	}

	//实现runnable接口。多线程实时更新进度条
	public class MyThread implements Runnable{

		//通知UI更新的消息

		//用来向UI线程传递进度的值
		Bundle data = new Bundle();

		//更新UI间隔时间
		int milliseconds = 100;
		double progress;
		@Override
		public void run() {
			// TODO Auto-generated method stub

			//用来标识是否还在播放状态，用来控制线程退出
			while(playStatus){  

                try {
                	//绑定成功才干開始更新UI
                    if(mBound){

                    	//发送消息，要求更新UI

                    	Message msg = new Message();
                    	data.clear();

                    	progress = mService.getProgress();
            			msg.what = 0;

            			data.putDouble("progress", progress);
            			msg.setData(data);
            			mHandler.sendMessage(msg);
                    }
                    Thread.sleep(milliseconds);
        			//Thread.currentThread().sleep(milliseconds);
					//每隔100ms更新一次UI

                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }  

			}
		}

	}

	 /** Defines callbacks for service binding, passed to bindService() */
    private ServiceConnection mConnection = new ServiceConnection() {  

        @Override
        public void onServiceConnected(ComponentName className,
                IBinder binder) {
            // We've bound to LocalService, cast the IBinder and get LocalService instance
        	MyBinder myBinder = (MyBinder) binder;

        	//获取service
        	mService = (MusicService) myBinder.getService();  

            //绑定成功
            mBound = true;  

            //开启线程，更新UI
            myThread.start();
        }  

        @Override
        public void onServiceDisconnected(ComponentName arg0) {
            mBound = false;
        }
    };  

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}

	@Override
	public void onDestroy(){
		//销毁activity时。要记得销毁线程
		playStatus = false;
		super.onDestroy();
	}

}

service的代码例如以下：

public class MusicService extends Service {

	IBinder musicBinder  = new MyBinder();

	//获取到activity的Handler。用来通知更新进度条
	Handler mHandler; 

	//播放音乐的媒体类
	MediaPlayer mediaPlayer;

	//本地歌曲的路径
    String path = "/storage/sdcard1/Music/浪漫满屋.mp3";

    private String TAG = "MyService";

	@Override
    public void onCreate() {
        super.onCreate();
        Log.d(TAG, "onCreate() executed");  

        init();

    }  

	@Override
	public IBinder onBind(Intent arg0) {
		// TODO Auto-generated method stub
	    //当绑定后。返回一个musicBinder
		return musicBinder;
	}

	class MyBinder extends Binder{

		public Service getService(){
			return MusicService.this;
		}
	}

	//初始化音乐播放
	void init(){
		//进入Idle
		mediaPlayer = new MediaPlayer();
		try {
			//初始化
			mediaPlayer.setDataSource(path);

			mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);  

			// prepare 通过异步的方式装载媒体资源
			mediaPlayer.prepareAsync();

		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

	//返回当前的播放进度，是double类型，即播放的百分比
	public double getProgress(){
		int position = mediaPlayer.getCurrentPosition();  

        int time = mediaPlayer.getDuration();  

        double progress = (double)position / (double)time;

        return progress;
	}

	//通过activity调节播放进度
	public void setProgress(int max , int dest){
		int time = mediaPlayer.getDuration();
		mediaPlayer.seekTo(time*dest/max);
	}

	//測试播放音乐
	public void play(){
		if(mediaPlayer != null){
			mediaPlayer.start();
		}

	}
	//暂停音乐
    public void pause() {
        if (mediaPlayer != null && mediaPlayer.isPlaying()) {
            mediaPlayer.pause();
        }
    }  

  //service 销毁时。停止播放音乐，释放资源
  	@Override
  	public void onDestroy() {
	     // 在activity结束的时候回收资源
	     if (mediaPlayer != null && mediaPlayer.isPlaying()) {
	         mediaPlayer.stop();
	         mediaPlayer.release();
	         mediaPlayer = null;
	     }
	     super.onDestroy();
     }
}

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