Camera preview is completely black after screen off, screen on

问题

I'm working with the CameraPreview in the API Demos that comes with the Android SDK. While the camera preview is running, if I turn off my screen and turn it on again, the camera preview is completely black. The device's camera application somehow manages to restore the camera preview, so there must be a way.

Not all devices I've tried exhibit this behavior. I can't confirm, but it seems like the OS version matters.

回答1:

You need to release and reacquire the camera in pause/resume. Here's some code from my CameraView widget:

public void onPause(){
    if(camera != null){
        camera.release();
        camera = null;
    }
}

public void onResume(){
    //Need to release if we already have one, or we won't get the camera
    if(camera != null){
        camera.release();
        camera = null;          
    }
    try {
        camera = Camera.open(); 
    }
    catch (Exception e){
    }

}

回答2:

What helped me was setContentView() in onResume().

It can be either

protected void onResume() {
    super.onResume();
    setContentView(R.layout.xxx);
    // ...
}

private View cachedContentView;
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    cachedContentView = doCreateContentView(getLayoutInflater());
    // ...
}
protected void onResume() {
    super.onResume();
    setContentView(cachedContentView);
    // ...
}

Both of them work.

回答3:

I had the same problem. Maybe, it isn't the best solution, but it works for me. In onPause() method restart your camera activity.

private boolean isBackPreesed = false;

@Override
public void onPause() {
    if (camera != null) {
        camera.release();
        camera = null;
    }

    if (!isBackPreesed) {
        finish();
        Intent restart = new Intent(this, this.getClass());
        startActivity(restart);
    }
}

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
    if (keyCode == KeyEvent.KEYCODE_BACK) {
        isBackPreesed = true;
    }       
    return super.onKeyDown(keyCode, event);
}

回答4:

My solution is release camera in surfaceDestroyed method not in onPause method and restart camera in surfaceCreated method .The result is fine.

来源：https://stackoverflow.com/questions/13385839/camera-preview-is-completely-black-after-screen-off-screen-on

标签

android

camera

surfaceview