Android SurfaceView的生命周期

本文利用SurfaceView来实现视频的播放

本文地址：http://www.cnblogs.com/wuyudong/p/5851156.html，转载请注明源地址。

在main.xml布局文件添加用于视频画面绘制的SurfaceView 控件：

<SurfaceView android:layout_width="fill_parent" android:layout_height="240dip" android:id="@+id/surfaceView" />

项目布局设计：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"tools:context=".MainActivity" ><EditTextandroid:id="@+id/et_path"android:layout_width="fill_parent"android:layout_height="wrap_content"android:hint="请输入视频文件的路径" /><LinearLayoutandroid:layout_width="fill_parent"android:layout_height="wrap_content"android:orientation="horizontal" ><Buttonandroid:id="@+id/bt_play"android:layout_width="0dip"android:layout_height="wrap_content"android:layout_weight="1"android:text="播放" /><Buttonandroid:id="@+id/bt_pause"android:layout_width="0dip"android:layout_height="wrap_content"android:layout_weight="1"android:text="暂停" /><Buttonandroid:id="@+id/bt_replay"android:layout_width="0dip"android:layout_height="wrap_content"android:layout_weight="1"android:text="重播" /><Buttonandroid:id="@+id/bt_stop"android:layout_width="0dip"android:layout_height="wrap_content"android:layout_weight="1"android:text="停止" /></LinearLayout><SurfaceView android:id="@+id/sv"android:layout_width="fill_parent"android:layout_height="fill_parent"/></LinearLayout>

大部分代码和《Android 多媒体播放API简介》中的完全一样，修改一点点代码即可：

public class MainActivity extends Activity implements OnClickListener {private EditText et_path;private Button bt_play, bt_replay, bt_pause, bt_stop;private SurfaceView sv;private MediaPlayer mediaPlayer;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);sv = (SurfaceView)findViewById(R.id.sv);et_path = (EditText) findViewById(R.id.et_path);bt_play = (Button) findViewById(R.id.bt_play);bt_replay = (Button) findViewById(R.id.bt_replay);bt_pause = (Button) findViewById(R.id.bt_pause);bt_stop = (Button) findViewById(R.id.bt_stop);bt_pause.setOnClickListener(this);bt_play.setOnClickListener(this);bt_replay.setOnClickListener(this);bt_stop.setOnClickListener(this);}@Overridepublic void onClick(View v) {switch (v.getId()) {case R.id.bt_play:play();break;case R.id.bt_replay:replay();break;case R.id.bt_stop:stop();break;case R.id.bt_pause:pause();break;default:break;}}/*** 暂停音乐*/private void pause() {if ("继续".equals(bt_pause.getText().toString().trim())) {mediaPlayer.start();bt_pause.setText("暂停");return;}if (mediaPlayer != null && mediaPlayer.isPlaying()) {mediaPlayer.pause();bt_pause.setText("继续");return;}}/*** 重新播放*/private void replay() {if (mediaPlayer != null && mediaPlayer.isPlaying()) {mediaPlayer.seekTo(0);return;}play();}/*** 停止播放音乐*/private void stop() {if (mediaPlayer != null && mediaPlayer.isPlaying()) {mediaPlayer.stop();mediaPlayer.release(); // 记得释放资源mediaPlayer = null;bt_play.setEnabled(true);}}/*** 播放音乐*/private void play() {String path = et_path.getText().toString().trim();File file = new File(path);if (file.exists() && file.length() > 0) {try {mediaPlayer = new MediaPlayer();mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);/* 设置Video影片以SurfaceHolder播放 */mediaPlayer.setDisplay(sv.getHolder());mediaPlayer.setDataSource(path);mediaPlayer.prepare(); // might take long! (for buffering, etc) mediaPlayer.start();mediaPlayer.setOnCompletionListener(new OnCompletionListener() {@Overridepublic void onCompletion(MediaPlayer mp) {bt_play.setEnabled(true);}} );bt_play.setEnabled(false);} catch (Exception e) {Toast.makeText(this, "播放失败", 0).show();e.printStackTrace();}} else {Toast.makeText(this, "文件不存在", 0).show();}}}

运行项目效果如下：

但是上面的代码有点问题，那就是当点击home或返回屏幕主界面后，在回到播放页面，视频黑屏

原因：

SurfaceView内部维护双缓冲，消耗内存资源

如果发现当前SurfaceView 用户可见的时候，创建SurfaceView的holder

如果SurfaceView变成用户不可见的时候  销毁SurfaceView的holder

为了观察SurfaceView的生命周期，可以添加下面的代码进行打印追踪：

sv.getHolder().addCallback(new Callback() {@Overridepublic void surfaceDestroyed(SurfaceHolder holder) {System.out.println("holder被销毁了");}@Overridepublic void surfaceCreated(SurfaceHolder holder) {System.out.println("holder被创建了");}@Overridepublic void surfaceChanged(SurfaceHolder holder, int format, int width,int height) {System.out.println("holder的大小变化了");}});}

logcat中打印下面的信息：

09-07 11:36:34.613: I/System.out(28858): holder被创建了
09-07 11:36:34.623: I/System.out(28858): holder的大小变化了

返回主界面

09-07 11:39:08.245: I/System.out(28858): holder被销毁了

再次回到视频界面

09-07 11:39:39.405: I/System.out(28858): holder被创建了
09-07 11:39:39.405: I/System.out(28858): holder的大小变化了

可以看到，每次回到视频界面，holder都会被重新创建

修改后的代码如下：

public class MainActivity extends Activity implements OnClickListener {private EditText et_path;private Button bt_play, bt_replay, bt_pause, bt_stop;private SurfaceView sv;private MediaPlayer mediaPlayer;private int currentPosition;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);sv = (SurfaceView) findViewById(R.id.sv);et_path = (EditText) findViewById(R.id.et_path);bt_play = (Button) findViewById(R.id.bt_play);bt_replay = (Button) findViewById(R.id.bt_replay);bt_pause = (Button) findViewById(R.id.bt_pause);bt_stop = (Button) findViewById(R.id.bt_stop);bt_pause.setOnClickListener(this);bt_play.setOnClickListener(this);bt_replay.setOnClickListener(this);bt_stop.setOnClickListener(this);sv.getHolder().addCallback(new Callback() {@Overridepublic void surfaceDestroyed(SurfaceHolder holder) {System.out.println("holder被销毁了");if (mediaPlayer != null && mediaPlayer.isPlaying()) {currentPosition = mediaPlayer.getCurrentPosition();stop();}}@Overridepublic void surfaceCreated(SurfaceHolder holder) {System.out.println("holder被创建了");if (currentPosition > 0) {play(currentPosition);}}@Overridepublic void surfaceChanged(SurfaceHolder holder, int format,int width, int height) {System.out.println("holder的大小变化了");}});}@Overridepublic void onClick(View v) {switch (v.getId()) {case R.id.bt_play:play(0);break;case R.id.bt_replay:replay();break;case R.id.bt_stop:stop();break;case R.id.bt_pause:pause();break;default:break;}}/*** 暂停音乐*/private void pause() {if ("继续".equals(bt_pause.getText().toString().trim())) {mediaPlayer.start();bt_pause.setText("暂停");return;}if (mediaPlayer != null && mediaPlayer.isPlaying()) {mediaPlayer.pause();bt_pause.setText("继续");return;}}/*** 重新播放*/private void replay() {if (mediaPlayer != null && mediaPlayer.isPlaying()) {mediaPlayer.seekTo(0);return;}play(0);}/*** 停止播放音乐*/private void stop() {if (mediaPlayer != null && mediaPlayer.isPlaying()) {mediaPlayer.stop();mediaPlayer.release(); // 记得释放资源mediaPlayer = null;bt_play.setEnabled(true);}}/*** 播放音乐*/private void play(final int currentPosition) {String path = et_path.getText().toString().trim();File file = new File(path);if (file.exists() && file.length() > 0) {try {mediaPlayer = new MediaPlayer();mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);/* 设置Video影片以SurfaceHolder播放 */mediaPlayer.setDisplay(sv.getHolder());mediaPlayer.setDataSource(path);mediaPlayer.prepare(); // might take long! (for buffering, etc) mediaPlayer.start();mediaPlayer.setOnPreparedListener(new OnPreparedListener() {@Overridepublic void onPrepared(MediaPlayer mp) {mediaPlayer.seekTo(currentPosition);}});mediaPlayer.setOnCompletionListener(new OnCompletionListener() {@Overridepublic void onCompletion(MediaPlayer mp) {bt_play.setEnabled(true);}});bt_play.setEnabled(false);} catch (Exception e) {Toast.makeText(this, "播放失败", 0).show();e.printStackTrace();}} else {Toast.makeText(this, "文件不存在", 0).show();}}}

 

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