Android SurfaceView plays video source code

SurfaceView

Let's first introduce how most software parses a video stream. First, it needs to determine the format of the video, which is related to decoding. Different formats of video are encoded differently, which is not the focus here. After knowing the encoding format of the video, it is decoded according to the encoding format, and finally a frame of images is obtained, and these images are quickly displayed on the interface, which is to play a video. SurfaceView in Android completes this function.

Since SurfaceView is used in conjunction with MediaPlayer, MediaPlayer also provides corresponding methods to set SurfaceView to display images. You only need to specify SurfaceView to display images for MediaPlayer. Its complete signature is as follows:

void setDisplay(SurfaceHolder sh)

It needs to pass a SurfaceHolder object. SurfaceHolder can be understood as a container for SurfaceView to load the frames of images that need to be displayed. It can be obtained through the SurfaceHolder.getHolder() method.

The steps for using MediaPlayer with SurfaceView to play videos are basically the same as using MediaPlayer to play MP3. You only need to set up the display SurfaceView.

SurfaceView double buffering

As mentioned above, SurfaceView, like most video applications, parses the video stream into frames for display. However, if this parsing process is completed in one thread, the next frame may not be parsed in time after the previous frame has been displayed, which will cause problems such as unsmooth images or asynchrony between sound and video. Therefore, SurfaceView, like most video applications, displays frames through a double buffering mechanism. So what is double buffering? Double buffering can be understood as two threads taking turns to parse the frame images of the video stream. When one thread finishes parsing the frame image, it renders the image into the interface, and at the same time, the other thread starts parsing the next frame image, so that the two threads take turns to parse the video stream to achieve a smooth playback effect.

SurfaceHolder

SurfaceView implements a double buffering mechanism internally, but this function consumes a lot of system memory. Due to the limitations of mobile devices, Android stipulates in its design that when SurfaceView is visible to the user, SurfaceHolder of SurfaceView is created to display the frame images parsed by the video stream. If SurfaceView becomes invisible to the user, SurfaceHolder of SurfaceView is destroyed immediately to save system resources.

If the developer does not maintain SurfaceHolder, after minimizing the program, when you open the application again, the sound of the video continues to play, but the picture is not displayed. This is because when the SurfaceView is not visible to the user, the previous SurfaceHolder has been destroyed. When you enter again, the SurfaceHolder on the interface is already a new SurfaceHolder. Therefore, SurfaceHolder requires our developers to code and maintain it. To maintain SurfaceHolder, you need to use its callback, SurfaceHolder.Callback(), which needs to implement the following three methods:

• void surfaceDestroyed(SurfaceHolder holder): callback when SurfaceHolder is destroyed.
• void surfaceCreated(SurfaceHolder holder): callback when SurfaceHolder is created.
• void surfaceChange(SurfaceHolder holder): Called back when the size of SurfaceHolder changes.

The following is the calling process of these three methods. These three methods are implemented for SurfaceHolder in the application. First enter the application, SurfaceHolder is created, and the size of SurfaceHolder is changed after creation. Then press the Home button to return to the desktop and destroy SurfaceHolder. Finally, enter the application again, recreate SurfaceHolder and change its size.

SurfaceView Demo Example

So much about SurfaceView has been talked about above. The following is a demo to demonstrate how SurfaceView plays videos. A scroll bar is added to show the progress. You can also drag the scroll bar to select the playback position. The comments of the Demo are relatively complete, so I will not repeat them here. The video is found randomly on the Internet. When running, make sure that there is this file in the directory /sdcard/ykzzldx.mp4.

Layout file: activity_main.xml

Implementation code:

 package cn.bgxt.surfaceviewdemo; 
  
 import java.io.File; 
  
 import android.media.AudioManager;
 import android.media.MediaPlayer;
 import android.media.MediaPlayer.OnCompletionListener;
 import android.media.MediaPlayer.OnErrorListener;
 import android.media.MediaPlayer.OnPreparedListener;
 import android.os.Bundle;
 import android.app.Activity;
 import android.util.Log;
 import android.view.SurfaceHolder;
 import android.view.SurfaceHolder.Callback;
 import android.view.SurfaceView;
 import android.view.View;
 import android.widget.Button;
 import android.widget.EditText;
 import android.widget.SeekBar;
 import android.widget.SeekBar.OnSeekBarChangeListener;
 import android.widget.Toast; 
  
 public   class MainActivity extends Activity {
 private   final String TAG = "main" ;
 private EditText et_path;
 private SurfaceView sv;
 private Button btn_play, btn_pause, btn_replay, btn_stop;
 private MediaPlayer mediaPlayer;
 private SeekBar seekBar;
 private   int currentPosition = 0 ;
 private   boolean isPlaying; 
  
 @Override  
 protected   void onCreate(Bundle savedInstanceState) {
 super .onCreate(savedInstanceState);
 setContentView(R.layout.activity_main); 
  
 seekBar = (SeekBar) findViewById(R.id.seekBar);
 sv = (SurfaceView) findViewById(R.id.sv);
 et_path = (EditText) findViewById(R.id.et_path); 
  
 btn_play = (Button) findViewById(R.id.btn_play);
 btn_pause = (Button) findViewById(R.id.btn_pause);
 btn_replay = (Button) findViewById(R.id.btn_replay);
 btn_stop = (Button) findViewById(R.id.btn_stop); 
  
 btn_play.setOnClickListener(click);
 btn_pause.setOnClickListener(click);
 btn_replay.setOnClickListener(click);
 btn_stop.setOnClickListener(click); 
  
 // Add callback for SurfaceHolder  
 sv.getHolder().addCallback(callback);
 // Properties that need to be set under version 4.0  
 // Set Surface not to maintain its own buffer, but wait for the screen's rendering engine to push content to the interface  
 // sv.getHolder().setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);  
 // Add progress change event to the progress bar  
 seekBar.setOnSeekBarChangeListener(change);
 } 
  
 private Callback callback = new Callback() {
 // Callback when SurfaceHolder is modified  
 @Override  
 public   void surfaceDestroyed(SurfaceHolder holder) {
 Log.i(TAG, "SurfaceHolder is destroyed" );
 // When destroying SurfaceHolder, record the current playback position and stop playback  
 if (mediaPlayer != null && mediaPlayer.isPlaying()) {
 currentPosition = mediaPlayer.getCurrentPosition();
 mediaPlayer.stop();
 }
 } 
  
 @Override  
 public   void surfaceCreated(SurfaceHolder holder) {
 Log.i(TAG, "SurfaceHolder is created" );
 if (currentPosition > 0 ) {
 // When creating SurfaceHolder, if the last playback position exists, play according to the last playback position  
 play(currentPosition);
 currentPosition = 0 ;
 }
 } 
  
 @Override  
 public   void surfaceChanged(SurfaceHolder holder, int format, int width,
 int height) {
 Log.i(TAG, "SurfaceHolder size changed" );
 } 
  
 }; 
  
 private OnSeekBarChangeListener change = new OnSeekBarChangeListener() { 
  
 @Override  
 public   void onStopTrackingTouch(SeekBar seekBar) {
 // Triggered when the progress bar stops modifying  
 // Get the current progress bar scale  
 int progress = seekBar.getProgress();
 if (mediaPlayer != null && mediaPlayer.isPlaying()) {
 // Set the current playback position  
 mediaPlayer.seekTo(progress);
 }
 } 
  
 @Override  
 public   void onStartTrackingTouch(SeekBar seekBar) { 
  
 } 
  
 @Override  
 public   void onProgressChanged(SeekBar seekBar, int progress,
 boolean fromUser) { 
  
 }
 }; 
  
 private View.OnClickListener click = new View.OnClickListener() { 
  
 @Override  
 public   void onClick(View v) { 
  
 switch (v.getId()) {
 case R.id.btn_play:
 play( 0 );
 break ;
 case R.id.btn_pause:
 pause();
 break ;
 case R.id.btn_replay:
 replay();
 break ;
 case R.id.btn_stop:
 stop();
 break ;
 default :
 break ;
 }
 }
 }; 
  
  
 /*
 * Stop playback
 */  
 protected   void stop() {
 if (mediaPlayer != null && mediaPlayer.isPlaying()) {
 mediaPlayer.stop();
 mediaPlayer.release();
 mediaPlayer = null ;
 btn_play.setEnabled( true );
 isPlaying = false ;
 }
 } 
  
 /**
 * Start playing
 *
 * @param msec initial playback position
 */  
 protected   void play( final   int msec) {
 // Get the video file address  
 String path = et_path.getText().toString().trim();
 File file = new File(path);
 if (!file.exists()) {
 Toast.makeText( this , "Video file path error" , 0 ).show();
 return ;
 }
 try {
 mediaPlayer = new MediaPlayer();
 mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
 // Set the video source for playback  
 mediaPlayer.setDataSource(file.getAbsolutePath());
 // Set the SurfaceHolder to display the video  
 mediaPlayer.setDisplay(sv.getHolder());
 Log.i(TAG, "Start loading" );
 mediaPlayer.prepareAsync();
 mediaPlayer.setOnPreparedListener( new OnPreparedListener() { 
  
 @Override  
 public   void onPrepared(MediaPlayer mp) {
 Log.i(TAG, "Loading completed" );
 mediaPlayer.start();
 // Play according to the initial position  
 mediaPlayer.seekTo(msec);
 // Set the maximum progress of the progress bar to the maximum playback time of the video stream  
 seekBar.setMax(mediaPlayer.getDuration());
 // Start the thread and update the progress bar scale  
 new Thread() { 
  
 @Override  
 public   void run() {
 try {
 isPlaying = true ;
 while (isPlaying) {
 int current = mediaPlayer
 .getCurrentPosition();
 seekBar.setProgress(current);
 sleep( 500 );
 }
 } catch (Exception e) {
 e.printStackTrace();
 }
 }
 }.start(); 
  
 btn_play.setEnabled( false );
 }
 });
 mediaPlayer.setOnCompletionListener( new OnCompletionListener() { 
  
 @Override  
 public   void onCompletion(MediaPlayer mp) {
 // Called back when playback is complete  
 btn_play.setEnabled( true );
 }
 }); 
  
 mediaPlayer.setOnErrorListener( new OnErrorListener() { 
  
 @Override  
 public   boolean onError(MediaPlayer mp, int what, int extra) {
 // Replay if an error occurs  
 play( 0 );
 isPlaying = false ;
 return   false ;
 }
 });
 } catch (Exception e) {
 e.printStackTrace();
 } 
  
 } 
  
 /**
 * Restart playback
 */  
 protected   void replay() {
 if (mediaPlayer != null && mediaPlayer.isPlaying()) {
 mediaPlayer.seekTo( 0 );
 Toast.makeText( this , "Replay" , 0 ).show();
 btn_pause.setText( "Pause" );
 return ;
 }
 isPlaying = false ;
 play( 0 ); 
  
 } 
  
 /**
 * Pause or Continue
 */  
 protected   void pause() {
 if (btn_pause.getText().toString().trim().equals( "continue" )) {
 btn_pause.setText( "Pause" );
 mediaPlayer.start();
 Toast.makeText( this , "Continue playing" , 0 ).show();
 return ;
 }
 if (mediaPlayer != null && mediaPlayer.isPlaying()) {
 mediaPlayer.pause();
 btn_pause.setText( "Continue" );
 Toast.makeText( this , "Pause playback" , 0 ).show();
 } 
  
 } 
  
 }

Source code download address: http://pan.baidu.com/s/1lgKLS

Original address: Android, SurfaceView video playback source code