学习broadcast和service结合练习做了一个小型播放器，本周出正式版

<pre name="code" class="java">package org.crazyit.broadcast;import android.app.Activity;import android.content.BroadcastReceiver;import android.content.Context;import android.content.Intent;import android.content.IntentFilter;import android.os.Bundle;import android.view.View;import android.view.View.OnClickListener;import android.widget.ImageButton;import android.widget.TextView;public class MusicBox extends Activity implements OnClickListener{// 获取界面中显示歌曲标题、作者文本框TextView title, author;// 播放/暂停、停止按钮ImageButton play, stop;ActivityReceiver activityReceiver;public static final String CTL_ACTION = "org.crazyit.action.CTL_ACTION";public static final String UPDATE_ACTION ="org.crazyit.action.UPDATE_ACTION";// 定义音乐的播放状态，0x11代表没有播放；0x12代表正在播放；0x13代表暂停int status = 0x11;String[] titleStrs = new String[] { "心愿", "约定", "美丽新世界" };String[] authorStrs = new String[] { "未知艺术家", "周蕙", "伍佰" };@Overridepublic void onCreate(Bundle savedInstanceState){super.onCreate(savedInstanceState);setContentView(R.layout.main);// 获取程序界面界面中的两个按钮play = (ImageButton) this.findViewById(R.id.play);stop = (ImageButton) this.findViewById(R.id.stop);title = (TextView) findViewById(R.id.title);author = (TextView) findViewById(R.id.author);// 为两个按钮的单击事件添加监听器play.setOnClickListener(this);stop.setOnClickListener(this);activityReceiver = new ActivityReceiver();// 创建IntentFilterIntentFilter filter = new IntentFilter();// 指定BroadcastReceiver监听的Actionfilter.addAction(UPDATE_ACTION);// 注册BroadcastReceiverregisterReceiver(activityReceiver, filter);Intent intent = new Intent(this, MusicService.class);// 启动后台ServicestartService(intent);}// 自定义的BroadcastReceiver，负责监听从Service传回来的广播public class ActivityReceiver extends BroadcastReceiver{@Overridepublic void onReceive(Context context, Intent intent){// 获取Intent中的update消息，update代表播放状态int update = intent.getIntExtra("update", -1);// 获取Intent中的current消息，current代表当前正在播放的歌曲int current = intent.getIntExtra("current", -1);if (current >= 0){title.setText(titleStrs[current]);author.setText(authorStrs[current]);}switch (update){case 0x11:play.setImageResource(R.drawable.play);status = 0x11;break;// 控制系统进入播放状态scase 0x12:// 播放状态下设置使用暂停图标play.setImageResource(R.drawable.pause);// 设置当前状态status = 0x12;break;// 控制系统进入暂停状态case 0x13:// 暂停状态下设置使用播放图标play.setImageResource(R.drawable.play);// 设置当前状态status = 0x13;break;}}}@Overridepublic void onClick(View source){// 创建IntentIntent intent = new Intent("org.crazyit.action.CTL_ACTION");switch (source.getId()){// 按下播放/暂停按钮case R.id.play:intent.putExtra("control", 1);break;// 按下停止按钮case R.id.stop:intent.putExtra("control", 2);break;}// 发送广播，将被Service组件中的BroadcastReceiver接收到sendBroadcast(intent);}}

//另外一个类

/** * */package org.crazyit.broadcast;import java.io.IOException;import android.app.Service;import android.content.BroadcastReceiver;import android.content.Context;import android.content.Intent;import android.content.IntentFilter;import android.content.res.AssetFileDescriptor;import android.content.res.AssetManager;import android.media.MediaPlayer;import android.media.MediaPlayer.OnCompletionListener;import android.os.IBinder;/** * Description: * <br/>网站: <a href="http://www.crazyit.org">疯狂Java联盟</a> * <br/>Copyright (C), 2001-2014, Yeeku.H.Lee * <br/>This program is protected by copyright laws. * <br/>Program Name: * <br/>Date: * @author Yeeku.H.Lee [e-mail] * @version 1.0 */public class MusicService extends Service{MyReceiver serviceReceiver;AssetManager am;String[] musics = new String[] { "wish.mp3", "promise.mp3","beautiful.mp3" };MediaPlayer mPlayer;// 当前的状态,0x11 代表没有播放 ；0x12代表 正在播放；0x13代表暂停int status = 0x11;// 记录当前正在播放的音乐int current = 0;@Overridepublic IBinder onBind(Intent intent){return null;}@Overridepublic void onCreate(){am = getAssets();// 创建BroadcastReceiverserviceReceiver = new MyReceiver();// 创建IntentFilterIntentFilter filter = new IntentFilter();filter.addAction(MusicBox.CTL_ACTION);registerReceiver(serviceReceiver, filter);// 创建MediaPlayermPlayer = new MediaPlayer();// 为MediaPlayer播放完成事件绑定监听器mPlayer.setOnCompletionListener(new OnCompletionListener() //①{@Overridepublic void onCompletion(MediaPlayer mp){current++;if (current >= 3){current = 0;}// 发送广播通知Activity更改文本框Intent sendIntent = new Intent(MusicBox.UPDATE_ACTION);sendIntent.putExtra("current", current);// 发送广播 ，将被Activity组件中的BroadcastReceiver接收到sendBroadcast(sendIntent);// 准备、并播放音乐prepareAndPlay(musics[current]);}});super.onCreate();}public class MyReceiver extends BroadcastReceiver{@Overridepublic void onReceive(final Context context, Intent intent){int control = intent.getIntExtra("control", -1);switch (control){// 播放或暂停case 1:// 原来处于没有播放状态if (status == 0x11){// 准备、并播放音乐prepareAndPlay(musics[current]);status = 0x12;}// 原来处于播放状态else if (status == 0x12){// 暂停mPlayer.pause();// 改变为暂停状态status = 0x13;}// 原来处于暂停状态else if (status == 0x13){// 播放mPlayer.start();// 改变状态status = 0x12;}break;// 停止声音case 2:// 如果原来正在播放或暂停if (status == 0x12 || status == 0x13){// 停止播放mPlayer.stop();status = 0x11;}}// 发送广播通知Activity更改图标、文本框Intent sendIntent = new Intent(MusicBox.UPDATE_ACTION);sendIntent.putExtra("update", status);sendIntent.putExtra("current", current);// 发送广播 ，将被Activity组件中的BroadcastReceiver接收到sendBroadcast(sendIntent);}}private void prepareAndPlay(String music){try{// 打开指定音乐文件AssetFileDescriptor afd = am.openFd(music);mPlayer.reset();// 使用MediaPlayer加载指定的声音文件。mPlayer.setDataSource(afd.getFileDescriptor(),afd.getStartOffset(), afd.getLength());// 准备声音mPlayer.prepare();// 播放mPlayer.start();}catch (IOException e){e.printStackTrace();}}}

最后即可实现简单的播放和停止功能

关键是两个broadcast之间信息的传输和获取