Android应用开发--MP3音乐播放器Service实现

让网友们久等啦，关于简、美音乐播放器的开发，最重要的Service类总算是要发博了。关于Android五大组件之一的Service在音乐播放器开发中得到了很好的应用，不仅是Service，广播（Broadcast）、Activity、Content Provider都会在此次开发中用到。所以说对于Android的一个很好的练手项目，音乐播放器是毋庸置疑的。上一篇，主要介绍的是播放界面的业务逻辑实现，不过这些业务逻辑都是以Service为中心的。





[java]
view plaincopyprint?

package com.wwj.sb.service;

import java.util.List;

import android.annotation.SuppressLint;
import android.app.Service;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.media.MediaPlayer;
import android.media.MediaPlayer.OnCompletionListener;
import android.media.MediaPlayer.OnPreparedListener;
import android.os.Handler;
import android.os.IBinder;
import android.util.Log;

import com.wwj.sb.activity.PlayerActivity;
import com.wwj.sb.domain.AppConstant;
import com.wwj.sb.domain.Mp3Info;
import com.wwj.sb.utils.MediaUtil;
/***
* 2013/5/25
* @author wwj
* 音乐播放服务
*/
@SuppressLint("NewApi")
public class PlayerService extends Service {
private MediaPlayer mediaPlayer; // 媒体播放器对象

private String path; // 音乐文件路径

private int msg;
private boolean isPause; // 暂停状态

private int current = 0; // 记录当前正在播放的音乐

private List<Mp3Info> mp3Infos; //存放Mp3Info对象的集合

private int status = 3; //播放状态，默认为顺序播放

private MyReceiver myReceiver; //自定义广播接收器

private int currentTime; //当前播放进度

private int duration; //播放长度

//服务要发送的一些Action
public static final String UPDATE_ACTION = "com.wwj.action.UPDATE_ACTION"; //更新动作

public static final String CTL_ACTION = "com.wwj.action.CTL_ACTION"; //控制动作

public static final String MUSIC_CURRENT = "com.wwj.action.MUSIC_CURRENT"; //当前音乐播放时间更新动作

public static final String MUSIC_DURATION = "com.wwj.action.MUSIC_DURATION";//新音乐长度更新动作

/**
* handler用来接收消息，来发送广播更新播放时间
*/
private Handler handler = new Handler() {
public void handleMessage(android.os.Message msg) {
if (msg.what == 1) {
if(mediaPlayer != null) {
currentTime = mediaPlayer.getCurrentPosition(); // 获取当前音乐播放的位置

Intent intent = new Intent();
intent.setAction(MUSIC_CURRENT);
intent.putExtra("currentTime", currentTime);
sendBroadcast(intent); // 给PlayerActivity发送广播

handler.sendEmptyMessageDelayed(1, 1000);
}

}
};
};

@Override
public void onCreate() {
super.onCreate();
Log.d("service", "service created");
mediaPlayer = new MediaPlayer();
mp3Infos = MediaUtil.getMp3Infos(PlayerService.this);

/**
* 设置音乐播放完成时的监听器
*/
mediaPlayer.setOnCompletionListener(new OnCompletionListener() {

@Override
public void onCompletion(MediaPlayer mp) {
if (status == 1) { // 单曲循环

mediaPlayer.start();
} else if (status == 2) { // 全部循环

current++;
if(current > mp3Infos.size() - 1) { //变为第一首的位置继续播放

current = 0;
}
Intent sendIntent = new Intent(UPDATE_ACTION);
sendIntent.putExtra("current", current);
// 发送广播，将被Activity组件中的BroadcastReceiver接收到

sendBroadcast(sendIntent);
path = mp3Infos.get(current).getUrl();
play(0);
} else if (status == 3) { // 顺序播放

current++; //下一首位置

if (current <= mp3Infos.size() - 1) {
Intent sendIntent = new Intent(UPDATE_ACTION);
sendIntent.putExtra("current", current);
// 发送广播，将被Activity组件中的BroadcastReceiver接收到

sendBroadcast(sendIntent);
path = mp3Infos.get(current).getUrl();
play(0);
}else {
mediaPlayer.seekTo(0);
current = 0;
Intent sendIntent = new Intent(UPDATE_ACTION);
sendIntent.putExtra("current", current);
// 发送广播，将被Activity组件中的BroadcastReceiver接收到

sendBroadcast(sendIntent);
}
} else if(status == 4) { //随机播放

current = getRandomIndex(mp3Infos.size() - 1);
System.out.println("currentIndex ->" + current);
Intent sendIntent = new Intent(UPDATE_ACTION);
sendIntent.putExtra("current", current);
// 发送广播，将被Activity组件中的BroadcastReceiver接收到

sendBroadcast(sendIntent);
path = mp3Infos.get(current).getUrl();
play(0);
}
}
});

myReceiver = new MyReceiver();
IntentFilter filter = new IntentFilter();
filter.addAction(PlayerActivity.CTL_ACTION);
registerReceiver(myReceiver, filter);
}

/**
* 获取随机位置
* @param end
* @return
*/
protected int getRandomIndex(int end) {
int index = (int) (Math.random() * end);
return index;
}

@Override
public IBinder onBind(Intent arg0) {
return null;
}

@Override
public void onStart(Intent intent, int startId) {
path = intent.getStringExtra("url"); //歌曲路径

current = intent.getIntExtra("listPosition", -1); //当前播放歌曲的在mp3Infos的位置

msg = intent.getIntExtra("MSG", 0); //播放信息

if (msg == AppConstant.PlayerMsg.PLAY_MSG) { //直接播放音乐

play(0);
} else if (msg == AppConstant.PlayerMsg.PAUSE_MSG) { //暂停

pause();
} else if (msg == AppConstant.PlayerMsg.STOP_MSG) { //停止

stop();
} else if (msg == AppConstant.PlayerMsg.CONTINUE_MSG) { //继续播放

resume();
} else if (msg == AppConstant.PlayerMsg.PRIVIOUS_MSG) { //上一首

previous();
} else if (msg == AppConstant.PlayerMsg.NEXT_MSG) { //下一首

next();
} else if (msg == AppConstant.PlayerMsg.PROGRESS_CHANGE) { //进度更新

currentTime = intent.getIntExtra("progress", -1);
play(currentTime);
} else if (msg == AppConstant.PlayerMsg.PLAYING_MSG) {
handler.sendEmptyMessage(1);
}
super.onStart(intent, startId);
}

/**
* 播放音乐
*
* @param position
*/
private void play(int currentTime) {
try {
mediaPlayer.reset();// 把各项参数恢复到初始状态

mediaPlayer.setDataSource(path);
mediaPlayer.prepare(); // 进行缓冲

mediaPlayer.setOnPreparedListener(new PreparedListener(currentTime));// 注册一个监听器

handler.sendEmptyMessage(1);
} catch (Exception e) {
e.printStackTrace();
}
}

/**
* 暂停音乐
*/
private void pause() {
if (mediaPlayer != null && mediaPlayer.isPlaying()) {
mediaPlayer.pause();
isPause = true;
}
}

private void resume() {
if (isPause) {
mediaPlayer.start();
isPause = false;
}
}

/**
* 上一首
*/
private void previous() {
Intent sendIntent = new Intent(UPDATE_ACTION);
sendIntent.putExtra("current", current);
// 发送广播，将被Activity组件中的BroadcastReceiver接收到

sendBroadcast(sendIntent);
play(0);
}

/**
* 下一首
*/
private void next() {
Intent sendIntent = new Intent(UPDATE_ACTION);
sendIntent.putExtra("current", current);
// 发送广播，将被Activity组件中的BroadcastReceiver接收到

sendBroadcast(sendIntent);
play(0);
}

/**
* 停止音乐
*/
private void stop() {
if (mediaPlayer != null) {
mediaPlayer.stop();
try {
mediaPlayer.prepare(); // 在调用stop后如果需要再次通过start进行播放,需要之前调用prepare函数

} catch (Exception e) {
e.printStackTrace();
}
}
}

@Override
public void onDestroy() {
if (mediaPlayer != null) {
mediaPlayer.stop();
mediaPlayer.release();
mediaPlayer = null;
}

}

/**
*
* 实现一个OnPrepareLister接口,当音乐准备好的时候开始播放
*
*/
private final class PreparedListener implements OnPreparedListener {
private int currentTime;

public PreparedListener(int currentTime) {
this.currentTime = currentTime;
}

@Override
public void onPrepared(MediaPlayer mp) {
mediaPlayer.start(); // 开始播放

if (currentTime > 0) { // 如果音乐不是从头播放

mediaPlayer.seekTo(currentTime);
}
Intent intent = new Intent();
intent.setAction(MUSIC_DURATION);
duration = mediaPlayer.getDuration();
intent.putExtra("duration", duration); //通过Intent来传递歌曲的总长度

sendBroadcast(intent);
}
}

public class MyReceiver extends BroadcastReceiver {

@Override
public void onReceive(Context context, Intent intent) {
int control = intent.getIntExtra("control", -1);
switch (control) {
case 1:
status = 1; // 将播放状态置为1表示：单曲循环

break;
case 2:
status = 2; //将播放状态置为2表示：全部循环

break;
case 3:
status = 3; //将播放状态置为3表示：顺序播放

break;
case 4:
status = 4; //将播放状态置为4表示：随机播放

break;
}
}
}

}

package com.wwj.sb.service;

import java.util.List;

import android.annotation.SuppressLint;
import android.app.Service;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.media.MediaPlayer;
import android.media.MediaPlayer.OnCompletionListener;
import android.media.MediaPlayer.OnPreparedListener;
import android.os.Handler;
import android.os.IBinder;
import android.util.Log;

import com.wwj.sb.activity.PlayerActivity;
import com.wwj.sb.domain.AppConstant;
import com.wwj.sb.domain.Mp3Info;
import com.wwj.sb.utils.MediaUtil;
/***
* 2013/5/25
* @author wwj
* 音乐播放服务
*/
@SuppressLint("NewApi")
public class PlayerService extends Service {
private MediaPlayer mediaPlayer; // 媒体播放器对象
private String path; 			// 音乐文件路径
private int msg;
private boolean isPause; 		// 暂停状态
private int current = 0; 		// 记录当前正在播放的音乐
private List<Mp3Info> mp3Infos;	//存放Mp3Info对象的集合
private int status = 3;			//播放状态，默认为顺序播放
private MyReceiver myReceiver;	//自定义广播接收器
private int currentTime;		//当前播放进度
private int duration;			//播放长度

//服务要发送的一些Action
public static final String UPDATE_ACTION = "com.wwj.action.UPDATE_ACTION";	//更新动作
public static final String CTL_ACTION = "com.wwj.action.CTL_ACTION";		//控制动作
public static final String MUSIC_CURRENT = "com.wwj.action.MUSIC_CURRENT";	//当前音乐播放时间更新动作
public static final String MUSIC_DURATION = "com.wwj.action.MUSIC_DURATION";//新音乐长度更新动作

/**
* handler用来接收消息，来发送广播更新播放时间
*/
private Handler handler = new Handler() {
public void handleMessage(android.os.Message msg) {
if (msg.what == 1) {
if(mediaPlayer != null) {
currentTime = mediaPlayer.getCurrentPosition(); // 获取当前音乐播放的位置
Intent intent = new Intent();
intent.setAction(MUSIC_CURRENT);
intent.putExtra("currentTime", currentTime);
sendBroadcast(intent); // 给PlayerActivity发送广播
handler.sendEmptyMessageDelayed(1, 1000);
}

}
};
};

@Override
public void onCreate() {
super.onCreate();
Log.d("service", "service created");
mediaPlayer = new MediaPlayer();
mp3Infos = MediaUtil.getMp3Infos(PlayerService.this);

/**
* 设置音乐播放完成时的监听器
*/
mediaPlayer.setOnCompletionListener(new OnCompletionListener() {

@Override
public void onCompletion(MediaPlayer mp) {
if (status == 1) { // 单曲循环
mediaPlayer.start();
} else if (status == 2) { // 全部循环
current++;
if(current > mp3Infos.size() - 1) {	//变为第一首的位置继续播放
current = 0;
}
Intent sendIntent = new Intent(UPDATE_ACTION);
sendIntent.putExtra("current", current);
// 发送广播，将被Activity组件中的BroadcastReceiver接收到
sendBroadcast(sendIntent);
path = mp3Infos.get(current).getUrl();
play(0);
} else if (status == 3) { // 顺序播放
current++;	//下一首位置
if (current <= mp3Infos.size() - 1) {
Intent sendIntent = new Intent(UPDATE_ACTION);
sendIntent.putExtra("current", current);
// 发送广播，将被Activity组件中的BroadcastReceiver接收到
sendBroadcast(sendIntent);
path = mp3Infos.get(current).getUrl();
play(0);
}else {
mediaPlayer.seekTo(0);
current = 0;
Intent sendIntent = new Intent(UPDATE_ACTION);
sendIntent.putExtra("current", current);
// 发送广播，将被Activity组件中的BroadcastReceiver接收到
sendBroadcast(sendIntent);
}
} else if(status == 4) {	//随机播放
current = getRandomIndex(mp3Infos.size() - 1);
System.out.println("currentIndex ->" + current);
Intent sendIntent = new Intent(UPDATE_ACTION);
sendIntent.putExtra("current", current);
// 发送广播，将被Activity组件中的BroadcastReceiver接收到
sendBroadcast(sendIntent);
path = mp3Infos.get(current).getUrl();
play(0);
}
}
});

myReceiver = new MyReceiver();
IntentFilter filter = new IntentFilter();
filter.addAction(PlayerActivity.CTL_ACTION);
registerReceiver(myReceiver, filter);
}

/**
* 获取随机位置
* @param end
* @return
*/
protected int getRandomIndex(int end) {
int index = (int) (Math.random() * end);
return index;
}

@Override
public IBinder onBind(Intent arg0) {
return null;
}

@Override
public void onStart(Intent intent, int startId) {
path = intent.getStringExtra("url");		//歌曲路径
current = intent.getIntExtra("listPosition", -1);	//当前播放歌曲的在mp3Infos的位置
msg = intent.getIntExtra("MSG", 0);			//播放信息
if (msg == AppConstant.PlayerMsg.PLAY_MSG) {	//直接播放音乐
play(0);
} else if (msg == AppConstant.PlayerMsg.PAUSE_MSG) {	//暂停
pause();
} else if (msg == AppConstant.PlayerMsg.STOP_MSG) {		//停止
stop();
} else if (msg == AppConstant.PlayerMsg.CONTINUE_MSG) {	//继续播放
resume();
} else if (msg == AppConstant.PlayerMsg.PRIVIOUS_MSG) {	//上一首
previous();
} else if (msg == AppConstant.PlayerMsg.NEXT_MSG) {		//下一首
next();
} else if (msg == AppConstant.PlayerMsg.PROGRESS_CHANGE) {	//进度更新
currentTime = intent.getIntExtra("progress", -1);
play(currentTime);
} else if (msg == AppConstant.PlayerMsg.PLAYING_MSG) {
handler.sendEmptyMessage(1);
}
super.onStart(intent, startId);
}

/**
* 播放音乐
*
* @param position
*/
private void play(int currentTime) {
try {
mediaPlayer.reset();// 把各项参数恢复到初始状态
mediaPlayer.setDataSource(path);
mediaPlayer.prepare(); // 进行缓冲
mediaPlayer.setOnPreparedListener(new PreparedListener(currentTime));// 注册一个监听器
handler.sendEmptyMessage(1);
} catch (Exception e) {
e.printStackTrace();
}
}

/**
* 暂停音乐
*/
private void pause() {
if (mediaPlayer != null && mediaPlayer.isPlaying()) {
mediaPlayer.pause();
isPause = true;
}
}

private void resume() {
if (isPause) {
mediaPlayer.start();
isPause = false;
}
}

/**
* 上一首
*/
private void previous() {
Intent sendIntent = new Intent(UPDATE_ACTION);
sendIntent.putExtra("current", current);
// 发送广播，将被Activity组件中的BroadcastReceiver接收到
sendBroadcast(sendIntent);
play(0);
}

/**
* 下一首
*/
private void next() {
Intent sendIntent = new Intent(UPDATE_ACTION);
sendIntent.putExtra("current", current);
// 发送广播，将被Activity组件中的BroadcastReceiver接收到
sendBroadcast(sendIntent);
play(0);
}

/**
* 停止音乐
*/
private void stop() {
if (mediaPlayer != null) {
mediaPlayer.stop();
try {
mediaPlayer.prepare(); // 在调用stop后如果需要再次通过start进行播放,需要之前调用prepare函数
} catch (Exception e) {
e.printStackTrace();
}
}
}

@Override
public void onDestroy() {
if (mediaPlayer != null) {
mediaPlayer.stop();
mediaPlayer.release();
mediaPlayer = null;
}

}

/**
*
* 实现一个OnPrepareLister接口,当音乐准备好的时候开始播放
*
*/
private final class PreparedListener implements OnPreparedListener {
private int currentTime;

public PreparedListener(int currentTime) {
this.currentTime = currentTime;
}

@Override
public void onPrepared(MediaPlayer mp) {
mediaPlayer.start(); // 开始播放
if (currentTime > 0) { // 如果音乐不是从头播放
mediaPlayer.seekTo(currentTime);
}
Intent intent = new Intent();
intent.setAction(MUSIC_DURATION);
duration = mediaPlayer.getDuration();
intent.putExtra("duration", duration);	//通过Intent来传递歌曲的总长度
sendBroadcast(intent);
}
}

public class MyReceiver extends BroadcastReceiver {

@Override
public void onReceive(Context context, Intent intent) {
int control = intent.getIntExtra("control", -1);
switch (control) {
case 1:
status = 1; // 将播放状态置为1表示：单曲循环
break;
case 2:
status = 2;	//将播放状态置为2表示：全部循环
break;
case 3:
status = 3;	//将播放状态置为3表示：顺序播放
break;
case 4:
status = 4;	//将播放状态置为4表示：随机播放
break;
}
}
}

}

以上的代码要注意的是在Service在被调用startService()方法会在回调onStart(),服务是不会被多次创建的，但会多次调用onStart方法，然而通过Intent传过来的数据，也只能在onStart方法内来接收。
似乎关于Service类没什么可说的，简单来说服务是我们看不见的东西，只是在后台不断运行的程序，音乐播放通过服务来实现，才不会在界面不可见的时候停掉，这是音乐播放器使用Service的原因。
第一阶段的音乐播放器开发已经到现在全部介绍完，第二阶段会实现歌词的显示和网络相关的下载和搜索，在这一阶段也会对UI进行一些细微的美化，尽量去尝试实现更炫的效果，比如提供主题的切换，界面切换的动画等等。小巫需要继续去学习，然后把所有东西分享给学习Android的朋友们，感谢你们的关注，让我们一起共同学习进步。
第二阶段具体会什么时候启动，还没有明确的时间，因为最近开始忙起来了，所以尽情等待吧。哇咔咔