Android Broadcast编写的音乐播放器

此播放器的播放操作交给后台执行，二者通过广播进行进行通信（双向通信），前台点击播放暂停停止按钮通过广播发送给后台，后台播放变换通过广播通知前台。

前台代码

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;

/**
 * Description:
 * <br/>site: <a href="http://www.crazyit.org">crazyit.org</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 kongyeeku@163.com
 * @version  1.0
 */
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" };

    @Override
    public 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IntentFilter
        IntentFilter filter = new IntentFilter();
        // 指定BroadcastReceiver监听的Action
        filter.addAction(UPDATE_ACTION);
        // 注册BroadcastReceiver
        registerReceiver(activityReceiver, filter);
        Intent intent = new Intent(this, MusicService.class);
        // 启动后台Service
        startService(intent);
    }

    // 自定义的BroadcastReceiver，负责监听从Service传回来的广播
    public class ActivityReceiver extends BroadcastReceiver
    {
        @Override
        public 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
                case 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;
            }
        }
    }

    @Override
    public void onClick(View source)
    {
        // 创建Intent
        Intent 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);
    }
}

后台服务

/**
 *
 */
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 kongyeeku@163.com
 * @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;

    @Override
    public IBinder onBind(Intent intent)
    {
        return null;
    }

    @Override
    public void onCreate()
    {
        am = getAssets();
        // 创建BroadcastReceiver
        serviceReceiver = new MyReceiver();
        // 创建IntentFilter
        IntentFilter filter = new IntentFilter();
        filter.addAction(MusicBox.CTL_ACTION);
        registerReceiver(serviceReceiver, filter);
        // 创建MediaPlayer
        mPlayer = new MediaPlayer();
        // 为MediaPlayer播放完成事件绑定监听器
        mPlayer.setOnCompletionListener(new OnCompletionListener() //①
        {
            @Override
            public 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
    {
        @Override
        public 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();
        }
    }
}

布局文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content">
<ImageButton
    android:id="@+id/play"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:src="@drawable/play"/>
<ImageButton 
    android:id="@+id/stop" 
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:src="@drawable/stop"/>
<LinearLayout
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">
<TextView
    android:id="@+id/title"
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content"
    android:textSize="25px"
    android:textColor="#ffffff"
    android:ellipsize="marquee"
    android:layout_weight="1"
    android:marqueeRepeatLimit="marquee_forever"/>
<TextView
    android:id="@+id/author"
    android:textSize="15px"
    android:gravity="center_vertical"
    android:layout_weight="1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"/>            
</LinearLayout>
</LinearLayout>

配置文件

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="org.crazyit.broadcast"
    android:versionCode="1"
    android:versionName="1.0">
    <uses-sdk
        android:minSdkVersion="10"
        android:targetSdkVersion="17" />
    <application android:icon="@drawable/ic_launcher" android:label="@string/app_name">
        <activity android:name=".MusicBox"
                android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <service android:name=".MusicService">
        </service>
    </application>
</manifest>