CODEWITHSUNDEEP
androidandroid-animation
Aharon Manne
Aharon Manne

Reputation: 712

SurfaceView.onDraw not called

I have implemented a number of similar activities, but for some reason, the following class is not reaching the onDraw call. The (very simple) class:

import ...etc.


public class SVPlay extends SurfaceView implements Callback {
Context context;
Point screenSize;
    Bitmap backGroundImage
public SVPlay(Context _context) {
    super(_context);
    context = _context;
    this.getHolder().addCallback(this);
    setFocusable(true);
    screenSize = DrawUtil.getInstance(context).getScreenSize();
    backgroundImage =  BitmapFactory.decodeResource(context.getResources(), R.drawable.room);
    backgroundImage = Bitmap.createScaledBitmap(backgroundImage, screenSize.x, screenSize.y, false);


}


@Override    public boolean onTouchEvent(MotionEvent event) {
    ...
}


@Override
protected void onDraw(Canvas canvas) {
    canvas.drawColor(0xFFAAAAAA);
    canvas.drawBitmap(backgroundImage, 0, 0, paint);

}



public void surfaceChanged(SurfaceHolder holder, int format, int width,
        int height) {
    // TODO Auto-generated method stub

}
public void surfaceCreated(SurfaceHolder holder) {
    setWillNotDraw(false);

}
public void surfaceDestroyed(SurfaceHolder holder) {
    // TODO Auto-generated method stub

}

}

This class is instantiated and run by an activity: public class PlayActivity extends Activity {

SVPlay svPlay;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    requestWindowFeature(Window.FEATURE_NO_TITLE);
            getWindow().addFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN);
    getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
    svPlay = new SVPlay(this);
    setContentView(svPlay);
}
....
}

This is similar to any number of other activity/surfaceView implementations that work for me, but for some reason onDraw is not called. To simplify the code for the purpose of the question, I eliminated the actual drawing activity, and test by setting a breakpoint in onDraw(). Execution does not reach the onDraw call. Adding a postInvalidate() call does not help. The constructor is called, and executes without any problems or exceptions. What is going on? 19/5/13 - Further investigation. This activity/SurfaceView is displayed when run as a separate project, so the problem isn't in the code displayed here, it's in the code that calls the activity. More soon...

Upvotes: 1

Views: 1837

Answers (2)

Aharon Manne
Aharon Manne

Reputation: 712

Thanks to Rob K for a helpful comment. In the end, after carefully doing the process from scratch, the problem went away. I'm not sure what I was doing wrong, but it apparently had to do with setting up the intent or calling StartActivityForResult().

Upvotes: 0

Rob K
Rob K

Reputation: 294

Does the visible state of your app need to constantly refresh as fast as possible (like a rapidly-changing game)? If not, there isn't really any need for a SurfaceView, as you can just call invalidate() when required then implement the onDraw(Canvas) method.

If you DO need to render continually and quickly, then it makes sense to use the SurfaceView. I think you need to add a SurfaceHolder object in your SurfaceView class (see http://developer.android.com/reference/android/view/SurfaceHolder.html). Use SurfaceHolder.lockCanvas() to access the Canvas to draw to, then draw to it using the normal Canvas drawing functions, then call unlockCanvasAndPost(Canvas). You would need to spawn a separate thread to handle the rendering, and the thread would need an ongoing loop where you would call lockCanvas() and unlockCanvasAndPost(Canvas).

Upvotes: 1

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