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);

}