Android, canvas: How do I clear (delete contents of) a canvas (= bitmaps), living in a surfaceView?

Draw transparent color with PorterDuff clear mode does the trick for what I wanted.

Canvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR)

How do I clear (or redraw) the WHOLE canvas for a new layout (= try at the game) ?

Just call Canvas.drawColor(Color.BLACK), or whatever color you want to clear your Canvas with.

And: how can I update just a part of the screen ?

There is no such method that just update a "part of the screen" since Android OS is redrawing every pixel when updating the screen. But, when you're not clearing old drawings on your Canvas, the old drawings are still on the surface and that is probably one way to "update just a part" of the screen.

So, if you want to "update a part of the screen", just avoid calling Canvas.drawColor() method.

Found this in google groups and this worked for me..

Paint clearPaint = new Paint();
clearPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
canvas.drawRect(0, 0, width, height, clearPaint); 

This removes drawings rectangles etc. while keeping set bitmap..