Android提高之MediaPlayer播放網絡視頻的實現方法

前面講解了MediaPlayer播放網絡音頻，主要介紹了MediaPlayer關於網絡音頻的緩沖和進度條控制的方法，本文再來講解一下MediaPlayer播放網絡視頻的方法。播放網絡視頻比播放網絡音頻需要多一個SurfaceView而已，在已經熟悉了MediaPlayer播放網絡音頻之後，相信大家對本文所述的播放網絡視頻也能很快地掌握。

先來看看本文程序運行截圖，如下所示：

本文程序的視頻來自http://daily3gp.com，大家可以替換程序中的視頻鏈接，試試其他影片。

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">
 <SurfaceView android:id="@+id/surfaceView1"
 android:layout_height="fill_parent" android:layout_width="fill_parent"></SurfaceView>
 <LinearLayout android:layout_height="wrap_content"
 android:layout_width="fill_parent" android:layout_gravity="bottom"
 android:orientation="vertical">
 <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="播放網絡視頻"></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”、“SurfaceHolder生命周期”等功能，其中“SurfaceHolder生命周期”是視頻與音頻播放的最大區別，通過surfaceCreated()、surfaceDestroyed()、surfaceChanged()可以創建/釋放某些資源。下面這個地方需要注意一下：

videoWidth = mediaPlayer.getVideoWidth();
videoHeight = mediaPlayer.getVideoHeight();
if (videoHeight != 0 && videoWidth != 0) {
 arg0.start();
}

有些視頻是android播放器不能播放的，不能播放時videoHeight=0，videoWidth=0，以此來判斷是否播放視頻。

Player.java源碼如下：

package com.videoplayer;
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.view.SurfaceHolder;
import android.view.SurfaceView;
import android.widget.SeekBar;
public class Player implements OnBufferingUpdateListener,
 OnCompletionListener, MediaPlayer.OnPreparedListener,
 SurfaceHolder.Callback {
 private int videoWidth;
 private int videoHeight;
 public MediaPlayer mediaPlayer;
 private SurfaceHolder surfaceHolder;
 private SeekBar skbProgress;
 private Timer mTimer=new Timer();
 public Player(SurfaceView surfaceView,SeekBar skbProgress)
 {
 this.skbProgress=skbProgress;
 surfaceHolder=surfaceView.getHolder();
 surfaceHolder.addCallback(this);
 surfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
 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
 public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2, int arg3) {
 Log.e("mediaPlayer", "surface changed");
 }
 @Override
 public void surfaceCreated(SurfaceHolder arg0) {
 try {
  mediaPlayer = new MediaPlayer();
  mediaPlayer.setDisplay(surfaceHolder);
  mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
  mediaPlayer.setOnBufferingUpdateListener(this);
  mediaPlayer.setOnPreparedListener(this);
 } catch (Exception e) {
  Log.e("mediaPlayer", "error", e);
 }
 Log.e("mediaPlayer", "surface created");
 }
 @Override
 public void surfaceDestroyed(SurfaceHolder arg0) {
 Log.e("mediaPlayer", "surface destroyed");
 }
 @Override
 /**
 * 通過onPrepared播放
 */
 public void onPrepared(MediaPlayer arg0) {
 videoWidth = mediaPlayer.getVideoWidth();
 videoHeight = mediaPlayer.getVideoHeight();
 if (videoHeight != 0 && videoWidth != 0) {
  arg0.start();
 }
 Log.e("mediaPlayer", "onPrepared");
 }

 @Override
 public void onCompletion(MediaPlayer arg0) {
 // TODO Auto-generated method stub
 }
 @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_videoplayer.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())*MediaPlayer.getDuration()。

test_videoplayer.java源碼如下：

package com.videoplayer;
import android.app.Activity;
import android.content.pm.ActivityInfo;
import android.net.Uri;
import android.os.Bundle;
import android.util.Log;
import android.view.SurfaceView;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.SeekBar;
public class test_videoplayer extends Activity {
 private SurfaceView surfaceView;
 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);
 setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
 surfaceView = (SurfaceView) this.findViewById(R.id.surfaceView1);

 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(surfaceView, skbProgress);
 }
 class ClickEvent implements OnClickListener {
 @Override
 public void onClick(View arg0) {
  if (arg0 == btnPause) {
  player.pause();
  } else if (arg0 == btnPlayUrl) {
  String url="http://daily3gp.com/vids/family_guy_penis_car.3gp";
  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);
 }
 }
}

感興趣的讀者可以自己動手測試一下本文實例代碼，相信對大家進行Android程序開發有一定的借鑒作用。