基于Service的简易音乐播放器

第一步：在MainActivity中获取XML中的组件并初始化界面点击事件，在MainActivity建一个ActivityReceiver继承BroadcastReceiver用以监听歌曲状态的变化从而更新UI，代码如下：

public class MainActivity extends Activity implements View.OnClickListener{
    TextView title,author,situation;
    Button play,stop;
    //  播放控制开始结束控制ACTION
    public static final String CTL_ACTION = "com.example.service_musicplayer.ctl_action";
    //  歌曲播放状态ACTION
    public static final String UPDATE_ACTION = "com.example.service_musicplayer.update_action";
    ActivityReceiver activityReceiver;
    //定义播放状态  0x11代表没有播放  0x12 代表正在播放  0x13代表暂停
    int status = 0x11;
    //  存放歌曲名
    String titleStr[] = {"Music-1","Music-2","Music-3"};
    //  存放歌手名
    String authorStr[] = {"author-1","author-2","author-3"};
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        play = (Button) findViewById(R.id.play);
        stop = (Button) findViewById(R.id.stop);
        title = (TextView) findViewById(R.id.title);
        author = (TextView) findViewById(R.id.author);
        situation = (TextView) findViewById(R.id.situation);
        play.setOnClickListener(this);
        stop.setOnClickListener(this);
        //  使用代码方式为broadcastReceiver注册监听
         activityReceiver = new ActivityReceiver();
        IntentFilter intentFilter = new IntentFilter();
        intentFilter.addAction(UPDATE_ACTION);
        //  注册broadcastReceiver
        registerReceiver(activityReceiver,intentFilter);
        Intent intent = new Intent(this,MusicService.class);
        startService(intent);
    }

    @Override
    public void onClick(View v) {
        Intent intent = new Intent();
        intent.setAction(CTL_ACTION);
        switch (v.getId()){
            case R.id.play:
                intent.putExtra("control",1);
                break;
            case R.id.stop:
                intent.putExtra("control",2);
                break;
        }

     "white-space:pre">   sendBroadcast(intent);
    }
    //   自定义BroadcastReceiver 监听Servicec传来的广播
    public class ActivityReceiver extends BroadcastReceiver{

        @Override
        public void onReceive(Context context, Intent intent) {
            String str = "";
            int update  = intent.getIntExtra("update",-1);
            int current = intent.getIntExtra("current",-1);
            if(current >= 0){
                title.setText(titleStr[current]);
                author.setText(authorStr[current]);
            }
            switch (update){
                case 0x11:
               //     status = 0x11;
                    str = "未播放";
                    break;
                case 0x12:
              //      status = 0x12;
                    str = "正在播放";
                    break;
                case 0x13:
               //     status = 0x13;
                    str = "暂停";
                    break;
            }
            situation.setText(str);
        }
    }
}

第二步：新建MusicService继承Service,MusicService中建了一个MyReceiver类继承BroadcastReceiver类用以监听歌曲播放状态的变化，以广播的方式将歌曲播放状态发出，在MainActivity中的ActivityReceiver能监听到此状态变化来更新UI，代码如下：

"font-size:18px;">public class MusicService extends Service {
    String musics[] = new String[]{"Leo Kayyu - Nokia Tune(Remix).mp3", "canon.mp3", "Cvked - iphone(Caked Up Mashup).mp3"};
    int current = 0;
    int status = 0x11; // 0x11不在播放状态  0x12正在播放  0x13暂停播放
    MediaPlayer mediaPlayer;
    AssetManager am;
    MyReceiver serviceReceiver;
    @Override
    public IBinder onBind(Intent intent) {

        return null;
    }

    @Override
    public void onCreate() {
        am = getAssets();
        serviceReceiver = new MyReceiver();
        //  代码方式为MyReceiver注册
        IntentFilter intentFilter = new IntentFilter();
        intentFilter.addAction(MainActivity.CTL_ACTION);
        registerReceiver(serviceReceiver,intentFilter);
        mediaPlayer = new MediaPlayer();
        mediaPlayer.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
            @Override
            public void onCompletion(MediaPlayer mp) {
                current++;
                if(current>=3) {
                    current = 0;
                }
                    Intent sendIntent = new Intent(MainActivity.UPDATE_ACTION);
                    sendIntent.putExtra("current",current);
                    sendBroadcast(sendIntent);
                    prepareAndPlay(musics[current]);
            }
        });
    }
    //   监听歌曲的播放状态，在歌曲播放状态改变时触发
    public class MyReceiver extends BroadcastReceiver{

        @Override
        public void onReceive(Context context, Intent intent) {
            int control = intent.getIntExtra("control",-1);
            switch(control){
                case 1:
                        //原来是没播放的状态
                    if(status == 0x11){
                        prepareAndPlay(musics[current]);
                        status = 0x12;
                        //原来处于播放状态
                    }else if(status == 0x12){
                        mediaPlayer.pause();
                        status = 0x13;
                        //  原来处于暂停状态
                    }else if(status == 0x13){
                        mediaPlayer.start();
                        status = 0x12;
                    }
                    break;
                case 2:
                    //  原来在播放或暂停状态
                    if(status == 0x12 || status == 0x13){
                        mediaPlayer.stop();
                        status = 0x11;
                    }
                    break;
            }
            Intent sendIntent = new Intent(MainActivity.UPDATE_ACTION);
            sendIntent.putExtra("update",status);
            sendIntent.putExtra("current",current);
            sendBroadcast(sendIntent);
        }
    }
    public void prepareAndPlay(String music){
        try {

"font-size:18px;">"white-space:pre">        mediaPlayer.reset();
            AssetFileDescriptor afd = am.openFd(URLEncoder.encode(music,"utf-8"));
            mediaPlayer.setDataSource(afd.getFileDescriptor(),afd.getStartOffset(),afd.getLength());
            // 准备声音
            mediaPlayer.prepare();
            // 播放
            mediaPlayer.start();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

附:程序的布局文件

xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.service_musicplayer.MainActivity">

    <TextView
        android:id="@+id/title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="歌名"
        android:textSize="20dp"/>
    <Button
        android:id="@+id/play"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="play"
        android:layout_below="@+id/title"/>
    <Button
        android:id="@+id/stop"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="stop"
        android:layout_toRightOf="@+id/play"
        android:layout_alignBaseline="@+id/play"/>
    <TextView
        android:id="@+id/author"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/play"
        android:text="作者/歌手"
        android:textSize="20dp"/>
    <TextView
        android:id="@+id/situation"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/play"
        android:text="播放状态"
        android:textSize="20dp"
        android:layout_toRightOf="@+id/author"
        android:layout_marginLeft="20dp"/>
RelativeLayout>

运行界面如下：

注意事项 ：歌曲文件放在assets文件下，使用Android studio 时没有assets文件就要自己新建一个assets文件，歌曲名不能有中文，另在程序中为两个广播注册了再配置文件中无须再注册，但记得在AndroidManifest.xml中注册service,注册注册代码为：

<service android:name=".MusicService"/>

(以上代码参照了安卓疯狂讲义，但是书上没讲音频文件应该放在哪里，自己新添了播放状态TextView)