前面有文章曾經地介紹過MediaPlayer的基本用法，這里就更加深入地講解MediaPlayer的在線播放功能。本文主要實現MediaPlayer在線播放音頻的功能，由于在線視頻播放比在線音頻播放復雜，因此先介紹在線音頻播放的實現，這樣可以幫助大家逐步深入了解MediaPlayer的在線播放功能。
先來看看本文程序運行的結果如下圖所示：
main.xml的源碼如下：
<?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="播放網絡音頻"></Button> <Button android:layout_height="wrap_content" android:id="@+id/btnPause" android:text="暫停" 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實現了“進度條更新”、“數據緩沖”等功能，雖然不是很復雜的功能，但卻是非常有用的功能。
Player.java源碼如下：
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); } /******************************************************* * 通過定時器和Handler來更新進度條 ******************************************************/ 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之后自動播放 //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 /** * 通過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，負責調用Player類，其中關鍵部分是SeekBarChangeEvent這個SeekBar拖動的事件：SeekBar的Progress是0~SeekBar.getMax()之內的數，而MediaPlayer.seekTo()的參數是0~MediaPlayer.getDuration()之內數，所以MediaPlayer.seekTo()的參數是(progress/seekBar.getMax())*player.mediaPlayer.getDuration()。
test_musicplayer.java源碼如下：
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("在線音樂播放---hellogv編寫"); 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里隨便搜索到的,大家可以試試別的鏈接 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()的參數是相對與影片時間的數字，而不是與seekBar.getMax()相對的數字 player.mediaPlayer.seekTo(progress); } }}感興趣的讀者可以親自動手調試一下本文實例代碼，相信會對大家理解Android程序設計起到一定的促進作用。
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