前面有文章曾经地介绍过MediaPlayer的基本用法，这里就更加深入地讲解MediaPlayer的在线播放功能。本文主要实现MediaPlayer在线播放音频的功能，由于在线视频播放比在线音频播放复杂，因此先介绍在线音频播放的实现，这样可以帮助大家逐步深入了解MediaPlayer的在线播放功能。
先来看看本文程序运行的结果如下图所示：
main.xml的源码如下：
<?xml version="1.0" encoding="utf-8"?> <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_height="fill_parent" android:layout_width="fill_parent"> <LinearLayout android:layout_height="wrap_content" android:layout_width="fill_parent" android:orientation="vertical" android:layout_gravity="top"> <LinearLayout android:orientation="horizontal" android:layout_gravity="center_horizontal" android:layout_marginTop="4.0dip" android:layout_height="wrap_content" android:layout_width="wrap_content"> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/btnPlayUrl" android:text="播放网络音频"></Button> <Button android:layout_height="wrap_content" android:id="@+id/btnPause" android:text="暂停" android:layout_width="80dip"></Button> <Button android:layout_height="wrap_content" android:layout_width="80dip" android:text="停止" android:id="@+id/btnStop"></Button> </LinearLayout> <LinearLayout android:orientation="horizontal" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_marginBottom="20dip"> <SeekBar android:paddingRight="10dip" android:layout_gravity="center_vertical" android:paddingLeft="10dip" android:layout_weight="1.0" android:layout_height="wrap_content" android:layout_width="wrap_content" android:id="@+id/skbProgress" android:max="100"></SeekBar> </LinearLayout> </LinearLayout> </FrameLayout>
Player.java是本文的核心，Player.java实现了“进度条更新”、“数据缓冲”等功能，虽然不是很复杂的功能，但却是非常有用的功能。
Player.java源码如下：
package com.musicplayer;
import java.io.IOException;
import java.util.Timer;
import java.util.TimerTask;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.media.MediaPlayer.OnBufferingUpdateListener;
import android.media.MediaPlayer.OnCompletionListener;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.widget.SeekBar;
public class Player implements OnBufferingUpdateListener,
OnCompletionListener, MediaPlayer.OnPreparedListener{
public MediaPlayer mediaPlayer;
private SeekBar skbProgress;
private Timer mTimer=new Timer();
public Player(SeekBar skbProgress)
{
this.skbProgress=skbProgress;
try {
mediaPlayer = new MediaPlayer();
mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
mediaPlayer.setOnBufferingUpdateListener(this);
mediaPlayer.setOnPreparedListener(this);
} catch (Exception e) {
Log.e("mediaPlayer", "error", e);
}
mTimer.schedule(mTimerTask, 0, 1000);
}
/*******************************************************
* 通过定时器和Handler来更新进度条
******************************************************/
TimerTask mTimerTask = new TimerTask() {
@Override
public void run() {
if(mediaPlayer==null)
return;
if (mediaPlayer.isPlaying() && skbProgress.isPressed() == false) {
handleProgress.sendEmptyMessage(0);
}
}
};
Handler handleProgress = new Handler() {
public void handleMessage(Message msg) {
int position = mediaPlayer.getCurrentPosition();
int duration = mediaPlayer.getDuration();
if (duration > 0) {
long pos = skbProgress.getMax() * position / duration;
skbProgress.setProgress((int) pos);
}
};
};
//*****************************************************
public void play()
{
mediaPlayer.start();
}
public void playUrl(String videoUrl)
{
try {
mediaPlayer.reset();
mediaPlayer.setDataSource(videoUrl);
mediaPlayer.prepare();//prepare之后自动播放
//mediaPlayer.start();
} catch (IllegalArgumentException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalStateException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public void pause()
{
mediaPlayer.pause();
}
public void stop()
{
if (mediaPlayer != null) {
mediaPlayer.stop();
mediaPlayer.release();
mediaPlayer = null;
}
}
@Override
/**
* 通过onPrepared播放
*/
public void onPrepared(MediaPlayer arg0) {
arg0.start();
Log.e("mediaPlayer", "onPrepared");
}
@Override
public void onCompletion(MediaPlayer arg0) {
Log.e("mediaPlayer", "onCompletion");
}
@Override
public void onBufferingUpdate(MediaPlayer arg0, int bufferingProgress) {
skbProgress.setSecondaryProgress(bufferingProgress);
int currentProgress=skbProgress.getMax()*mediaPlayer.getCurrentPosition()/mediaPlayer.getDuration();
Log.e(currentProgress+"% play", bufferingProgress + "% buffer");
}
}
test_musicplayer.java是主程序，负责调用Player类，其中关键部分是SeekBarChangeEvent这个SeekBar拖动的事件：SeekBar的Progress是0~SeekBar.getMax()之内的数，而MediaPlayer.seekTo()的参数是0~MediaPlayer.getDuration()之内数，所以MediaPlayer.seekTo()的参数是(progress/seekBar.getMax())*player.mediaPlayer.getDuration()。
test_musicplayer.java源码如下：
package com.musicplayer;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.SeekBar;
public class test_musicplayer extends Activity {
private Button btnPause, btnPlayUrl, btnStop;
private SeekBar skbProgress;
private Player player;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
this.setTitle("在线音乐播放---hellogv编写");
btnPlayUrl = (Button) this.findViewById(R.id.btnPlayUrl);
btnPlayUrl.setOnClickListener(new ClickEvent());
btnPause = (Button) this.findViewById(R.id.btnPause);
btnPause.setOnClickListener(new ClickEvent());
btnStop = (Button) this.findViewById(R.id.btnStop);
btnStop.setOnClickListener(new ClickEvent());
skbProgress = (SeekBar) this.findViewById(R.id.skbProgress);
skbProgress.setOnSeekBarChangeListener(new SeekBarChangeEvent());
player = new Player(skbProgress);
}
class ClickEvent implements OnClickListener {
@Override
public void onClick(View arg0) {
if (arg0 == btnPause) {
player.pause();
} else if (arg0 == btnPlayUrl) {
//在百度MP3里随便搜索到的,大家可以试试别的链接
String url="http://219.138.125.22/myweb/mp3/CMP3/JH19.MP3";
player.playUrl(url);
} else if (arg0 == btnStop) {
player.stop();
}
}
}
class SeekBarChangeEvent implements SeekBar.OnSeekBarChangeListener {
int progress;
@Override
public void onProgressChanged(SeekBar seekBar, int progress,
boolean fromUser) {
// 原本是(progress/seekBar.getMax())*player.mediaPlayer.getDuration()
this.progress = progress * player.mediaPlayer.getDuration()
/ seekBar.getMax();
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
// seekTo()的参数是相对与影片时间的数字，而不是与seekBar.getMax()相对的数字
player.mediaPlayer.seekTo(progress);
}
}
}
感兴趣的读者可以亲自动手调试一下本文实例代码，相信会对大家理解Android程序设计起到一定的促进作用。
