Android提高之MediaPlayer播放網絡音頻的實現方法

前面有文章曾經地介紹過MediaPlayer的基本用法，這裡就更加深入地講解MediaPlayer的在線播放功能。本文主要實現MediaPlayer在線播放音頻的功能，由於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之後自動播放
  //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裡隨便搜索到的,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。