Android应用开发--MP3音乐播放器代码实现（一）

需求1：将内存卡中的MP3音乐读取出来并显示到列表当中

1.   从数据库中查询所有音乐数据，保存到List集合当中，List当中存放的是Mp3Info对象
2.   迭代List集合，把每一个Mp3Info对象的所有属性，保存到Map对象当中
3.   定义一个List集合，把Map对象添加到List集合当中
4.   通过定义一个SimpleAdpter,调用setAdpter方法，将数据显示到列表当中

[java]
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/**
* 用于从数据库中查询歌曲的信息，保存在List当中
*
* @return
*/
public List<Mp3Info> getMp3Infos() {
Cursor cursor = getContentResolver().query(
MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, null, null, null,
MediaStore.Audio.Media.DEFAULT_SORT_ORDER);
List<Mp3Info> mp3Infos = new ArrayList<Mp3Info>();
for (int i = 0; i < cursor.getCount(); i++) {
Mp3Info mp3Info = new Mp3Info();
cursor.moveToNext();
long id = cursor.getLong(cursor
.getColumnIndex(MediaStore.Audio.Media._ID)); //音乐id

String title = cursor.getString((cursor
.getColumnIndex(MediaStore.Audio.Media.TITLE)));//音乐标题

String artist = cursor.getString(cursor
.getColumnIndex(MediaStore.Audio.Media.ARTIST));//艺术家

long duration = cursor.getLong(cursor
.getColumnIndex(MediaStore.Audio.Media.DURATION));//时长

long size = cursor.getLong(cursor
.getColumnIndex(MediaStore.Audio.Media.SIZE)); //文件大小

String url = cursor.getString(cursor
.getColumnIndex(MediaStore.Audio.Media.DATA)); //文件路径

int isMusic = cursor.getInt(cursor
.getColumnIndex(MediaStore.Audio.Media.IS_MUSIC));//是否为音乐

if (isMusic != 0) { //只把音乐添加到集合当中

mp3Info.setId(id);
mp3Info.setTitle(title);
mp3Info.setArtist(artist);
mp3Info.setDuration(duration);
mp3Info.setSize(size);
mp3Info.setUrl(url);
mp3Infos.add(mp3Info);
}
}
return mp3Infos;
}

/**
* 用于从数据库中查询歌曲的信息，保存在List当中
*
* @return
*/
public List<Mp3Info> getMp3Infos() {
Cursor cursor = getContentResolver().query(
MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, null, null, null,
MediaStore.Audio.Media.DEFAULT_SORT_ORDER);
List<Mp3Info> mp3Infos = new ArrayList<Mp3Info>();
for (int i = 0; i < cursor.getCount(); i++) {
Mp3Info mp3Info = new Mp3Info();
cursor.moveToNext();
long id = cursor.getLong(cursor
.getColumnIndex(MediaStore.Audio.Media._ID));	//音乐id
String title = cursor.getString((cursor
.getColumnIndex(MediaStore.Audio.Media.TITLE)));//音乐标题
String artist = cursor.getString(cursor
.getColumnIndex(MediaStore.Audio.Media.ARTIST));//艺术家
long duration = cursor.getLong(cursor
.getColumnIndex(MediaStore.Audio.Media.DURATION));//时长
long size = cursor.getLong(cursor
.getColumnIndex(MediaStore.Audio.Media.SIZE));	//文件大小
String url = cursor.getString(cursor
.getColumnIndex(MediaStore.Audio.Media.DATA));				//文件路径
int isMusic = cursor.getInt(cursor
.getColumnIndex(MediaStore.Audio.Media.IS_MUSIC));//是否为音乐
if (isMusic != 0) {		//只把音乐添加到集合当中
mp3Info.setId(id);
mp3Info.setTitle(title);
mp3Info.setArtist(artist);
mp3Info.setDuration(duration);
mp3Info.setSize(size);
mp3Info.setUrl(url);
mp3Infos.add(mp3Info);
}
}
return mp3Infos;
}

[java]
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/** * 填充列表 * @param mp3Infos */ public void setListAdpter(List<Mp3Info> mp3Infos) { List<HashMap<String, String>> mp3list = new ArrayList<HashMap<String, String>>(); for (Iterator iterator = mp3Infos.iterator(); iterator.hasNext();) { Mp3Info mp3Info = (Mp3Info) iterator.next(); HashMap<String, String> map = new HashMap<String, String>(); map.put("title", mp3Info.getTitle()); map.put("Artist", mp3Info.getArtist()); map.put("duration", String.valueOf(mp3Info.getDuration())); map.put("size", String.valueOf(mp3Info.getSize())); map.put("url", mp3Info.getUrl()); mp3list.add(map); } mAdapter = new SimpleAdapter(this, mp3list, R.layout.music_list_item_layout, new String[] { "title", "Artist", "duration" }, new int[] { R.id.music_title, R.id.music_Artist, R.id.music_duration }); mMusiclist.setAdapter(mAdapter); }

/**
* 填充列表
* @param mp3Infos
*/
public void setListAdpter(List<Mp3Info> mp3Infos) {
List<HashMap<String, String>> mp3list = new ArrayList<HashMap<String, String>>();
for (Iterator iterator = mp3Infos.iterator(); iterator.hasNext();) {
Mp3Info mp3Info = (Mp3Info) iterator.next();
HashMap<String, String> map = new HashMap<String, String>();
map.put("title", mp3Info.getTitle());
map.put("Artist", mp3Info.getArtist());
map.put("duration", String.valueOf(mp3Info.getDuration()));
map.put("size", String.valueOf(mp3Info.getSize()));
map.put("url", mp3Info.getUrl());
mp3list.add(map);
}
mAdapter = new SimpleAdapter(this, mp3list,
R.layout.music_list_item_layout, new String[] { "title", "Artist", "duration" },
new int[] { R.id.music_title, R.id.music_Artist, R.id.music_duration });
mMusiclist.setAdapter(mAdapter);
}

实现效果如图：



需求2：点击列表的每一项，启动一个服务来播放音乐

1. 注册条目点击监听器OnItemClickListener

2. 定义一个实现OnItemClickListener接口的内部类

3. 定义一个继承Service的服务类PlayerServie

1. 注册条目点击监听器OnItemClickListener

[java]
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mMusiclist = (ListView) findViewById(R.id.music_list); mMusiclist.setOnItemClickListener(new MusicListItemClickListener()); mp3Infos = getMp3Infos(); setListAdpter(getMp3Infos());

mMusiclist = (ListView) findViewById(R.id.music_list);
mMusiclist.setOnItemClickListener(new MusicListItemClickListener());
mp3Infos = getMp3Infos();
setListAdpter(getMp3Infos());

2. 定义一个实现OnItemClickListener接口的内部类

[java]
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private class MusicListItemClickListener implements OnItemClickListener {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
if(mp3Infos != null) {
Mp3Info mp3Info = mp3Infos.get(position);
Log.d("mp3Info-->", mp3Info.toString());
Intent intent = new Intent();
intent.putExtra("url", mp3Info.getUrl());
intent.putExtra("MSG", AppConstant.PlayerMsg.PLAY_MSG);
intent.setClass(MainActivity.this, PlayerService.class);
startService(intent); //启动服务

}
}
}

private class MusicListItemClickListener implements OnItemClickListener {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
if(mp3Infos != null) {
Mp3Info mp3Info = mp3Infos.get(position);
Log.d("mp3Info-->", mp3Info.toString());
Intent intent = new Intent();
intent.putExtra("url", mp3Info.getUrl());
intent.putExtra("MSG", AppConstant.PlayerMsg.PLAY_MSG);
intent.setClass(MainActivity.this, PlayerService.class);
startService(intent);		//启动服务
}
}
}

3. 定义一个继承Service的服务类PlayerServie（未完善的Service类）

[java]
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package com.wwj.sb.service;

import android.annotation.SuppressLint;
import android.app.Service;
import android.content.Intent;
import android.media.MediaPlayer;
import android.media.MediaPlayer.OnPreparedListener;
import android.os.IBinder;

import com.wwj.sb.domain.AppConstant;

@SuppressLint("NewApi")
public class PlayerService extends Service {
private MediaPlayer mediaPlayer = new MediaPlayer(); //媒体播放器对象

private String path; //音乐文件路径

private boolean isPause; //暂停状态

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

@Override
public int onStartCommand(Intent intent, int flags, int startId) {
if(mediaPlayer.isPlaying()) {
stop();
}
path = intent.getStringExtra("url");
int msg = intent.getIntExtra("MSG", 0);
if(msg == AppConstant.PlayerMsg.PLAY_MSG) {
play(0);
} else if(msg == AppConstant.PlayerMsg.PAUSE_MSG) {
pause();
} else if(msg == AppConstant.PlayerMsg.STOP_MSG) {
stop();
}
return super.onStartCommand(intent, flags, startId);
}

/**
* 播放音乐
* @param position
*/
private void play(int position) {
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(position));//注册一个监听器

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

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

/**
* 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();
}
}
/**
*
* 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 positon;

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

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

if(positon > 0) { //如果音乐不是从头播放

mediaPlayer.seekTo(positon);
}
}
}

}

package com.wwj.sb.service;

import android.annotation.SuppressLint;
import android.app.Service;
import android.content.Intent;
import android.media.MediaPlayer;
import android.media.MediaPlayer.OnPreparedListener;
import android.os.IBinder;

import com.wwj.sb.domain.AppConstant;

@SuppressLint("NewApi")
public class PlayerService extends Service {
private MediaPlayer mediaPlayer =  new MediaPlayer();		//媒体播放器对象
private String path;						//音乐文件路径
private boolean isPause;					//暂停状态

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

@Override
public int onStartCommand(Intent intent, int flags, int startId) {
if(mediaPlayer.isPlaying()) {
stop();
}
path = intent.getStringExtra("url");
int msg = intent.getIntExtra("MSG", 0);
if(msg == AppConstant.PlayerMsg.PLAY_MSG) {
play(0);
} else if(msg == AppConstant.PlayerMsg.PAUSE_MSG) {
pause();
} else if(msg == AppConstant.PlayerMsg.STOP_MSG) {
stop();
}
return super.onStartCommand(intent, flags, startId);
}

/**
* 播放音乐
* @param position
*/
private void play(int position) {
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(position));//注册一个监听器
}
catch (Exception e) {
e.printStackTrace();
}
}

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

/**
* 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();
}
}
/**
*
* 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 positon;

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

@Override
public void onPrepared(MediaPlayer mp) {
mediaPlayer.start();	//开始播放
if(positon > 0) {	//如果音乐不是从头播放
mediaPlayer.seekTo(positon);
}
}
}

}

以上代码实现了两个需求，显示音乐列表和实现列表点击事件启动Servic。下次会实现控制音乐播放的需求。