CODEWITHSUNDEEP
androidsurfaceview
roiberg
roiberg

Reputation: 13747

Resume to SurfaceView shows black screen

All is ok, when I have started my application. But when I go to the next activity and come back the SurfaceView it looks like black. When I debug, I can see the lines that need to draw on the canvas running but nothing shows up.
Here is my code:

public class DrawView extends SurfaceView implements Runnable
{

    Thread thread = null;
    SurfaceHolder holder;
    Bitmap background;
    Canvas canvas;
    Matrix matrixUP = new Matrix();
    Matrix matrixDOWN = new Matrix();
    boolean ok = false;

    public DrawView(Context context) 
    {
        super(context);
        holder = getHolder();
    }

    public void run() 
    {
        while(ok)
        {
            if(!holder.getSurface().isValid())
            {
                continue;
            }
            watch_hand = Bitmap.createScaledBitmap(watch_hand, width/4, height/6, false);
            watch_hand_down = Bitmap.createScaledBitmap(watch_hand_down, width/4, height/6, false);
            background = BitmapFactory.decodeResource(getResources(), R.drawable.needles);
            background = Bitmap.createScaledBitmap(background, width, height/2+20, false);
            canvas = holder.lockCanvas();
            matrixUP.setTranslate(CENTER_X - watch_hand.getWidth()/2, height/4 - watch_hand.getHeight() - 40);
            matrixUP.preRotate((float) degreUP , watch_hand.getWidth()/2 , watch_hand.getHeight()-10);

            matrixDOWN.setTranslate(CENTER_X - watch_hand_down.getWidth()/2, height/2 - watch_hand_down.getHeight() - 20);
            matrixDOWN.preRotate((float) degreDOWN , watch_hand_down.getWidth()/2 , 10);

            canvas.drawARGB(255, 255, 255, 255);
            canvas.drawBitmap(background, 0, 0, null);
            canvas.drawBitmap(watch_hand, matrixUP, null);
            canvas.drawBitmap(watch_hand_down, matrixDOWN, null);
            holder.unlockCanvasAndPost(canvas);
        }           
    }

    public void pause()
    {
        ok = false;
        while(true)
        {
            try
            {
                thread.join();
            }catch (InterruptedException e)
            {
                e.printStackTrace();
            }
            break;
        }
        thread = null;
    }

    public void resume()
    {
        ok = true;
        thread = new Thread(this);
        thread.start();
    }           
}

as you see I'm using a resume and pause function. They are called from the onCreate. Why is it happening and how can I fix this?

Thanks!

Upvotes: 3

Views: 8215

Answers (2)

Chaitanya
Chaitanya

Reputation: 3469

Call resume() and pause() methods of the surface view(in your case DrawView) from onResume() and onPause() methods of the activity in which the surface view is present. U mentioned that your were calling from onCreate().

This should solve the issue.

Upvotes: 0

onur güngör
onur güngör

Reputation: 715

The answer depends on how you change to the other activity.

Basically, you have to think about how to store the current state of the surface when the activity pauses, stops or destroys.

for example you can overload onSaveInstanceState in your activity to save degreUP and degreDOWN (by the way they are not defined in the current code snippet). and restore them in onRestoreInstanceState. see Saving Android Activity state using Save Instance State

Upvotes: 1

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