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" >

    <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();
        }

    }

}