You should avoid creating a new paint every time though, which is why I mentioned the drawColor() alternative.
On Sun, Nov 25, 2012 at 4:57 PM, Johan <[email protected]> wrote: > Thanks for the hint! Work's perfectly. > > paint.setXfermode(new PorterDuffXfermode(Mode.CLEAR)); > canvas.drawPaint(paint); > > > On Monday, November 26, 2012 11:31:12 AM UTC+11, Romain Guy (Google) wrote: >> >> Surfaces are double (or even triple) buffered. You are indeed not getting >> in your canvas what's currently on screen but what was on screen a frame >> ago. The easiest way to clear the surface is to call canvas.drawColor(0, >> PorterDuff.Mode.CLEAR) (you can also use 0xff000000, PorterDuff.Mode.SRC). >> >> >> On Sun, Nov 25, 2012 at 3:42 PM, Johan <[email protected]> wrote: >> >>> I have some strange behaviour when repainting the screen with my live >>> wallpaper. I'm scaling an image and drawing it to the screen, but on each >>> draw (as the image is scaled smaller than the previous draw), I can still >>> see the previous image below the new image. >>> How do I clear the previous image out so that only the new scaled image >>> is displayed? >>> >>> This is my code: >>> >>> private final Runnable mDraw = new Runnable() { >>> public void run() { >>> draw(); >>> } >>> }; >>> >>> void draw() { >>> SurfaceHolder holder = getSurfaceHolder(); >>> Canvas canvas = null; >>> try { >>> canvas = holder.lockCanvas(); >>> if(canvas != null) { >>> this.paintScreen(canvas); >>> } >>> }finally { >>> if(canvas != null) { >>> holder.unlockCanvasAndPost(**canvas); >>> } >>> } >>> mHandler.removeCallbacks(**mDraw); >>> if (mVisible) { >>> mHandler.postDelayed(mDraw, 60000); >>> } >>> } >>> >>> Every minute my paintSurface function scales a bitmap (image loaded from >>> resources), then uses canvas.drawBitmap to put the image on the screen. As >>> I understand from the documentation, holde.lockCanvas()is not supposed to >>> contain the image currently on the screen and every pixel has to be >>> drawn... this doesn't seem to be the case since the previous pixels are >>> obviously under the new pixels. >>> >>> Thanks, >>> J >>> (26 Sept '12 - 10:45 AM) >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "Android Developers" group. >>> To post to this group, send email to android-d...@**googlegroups.com >>> To unsubscribe from this group, send email to >>> android-developers+**[email protected] >>> For more options, visit this group at >>> http://groups.google.com/**group/android-developers?hl=en<http://groups.google.com/group/android-developers?hl=en> >> >> >> >> >> -- >> Romain Guy >> Android framework engineer >> [email protected] >> >> -- > You received this message because you are subscribed to the Google > Groups "Android Developers" group. > To post to this group, send email to [email protected] > To unsubscribe from this group, send email to > [email protected] > For more options, visit this group at > http://groups.google.com/group/android-developers?hl=en -- Romain Guy Android framework engineer [email protected] -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
