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Android SurfaceView的生命周期
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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" > <EditText
android: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" /> <LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" > <Button
android:id="@+id/bt_play"
android:layout_width="0dip"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="播放" /> <Button
android:id="@+id/bt_pause"
android:layout_width="0dip"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="暂停" /> <Button
android:id="@+id/bt_replay"
android:layout_width="0dip"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="重播" /> <Button
android: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;
@Override
protected 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);
}
@Override
public 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() {
@Override
public 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() {
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
System.out.println("holder被销毁了");
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
System.out.println("holder被创建了");
}
@Override
public 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;
@Override
protected 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() {
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
System.out.println("holder被销毁了");
if (mediaPlayer != null && mediaPlayer.isPlaying()) {
currentPosition = mediaPlayer.getCurrentPosition();
stop();
}
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
System.out.println("holder被创建了");
if (currentPosition > 0) {
play(currentPosition);
}
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format,
int width, int height) {
System.out.println("holder的大小变化了");
}
});
}
@Override
public 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() {
@Override
public void onPrepared(MediaPlayer mp) {
mediaPlayer.seekTo(currentPosition);
}
});
mediaPlayer.setOnCompletionListener(new OnCompletionListener() {
@Override
public 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();
}
}
}
