<https://lh3.googleusercontent.com/-yKMQ9N8KA7k/VthdtfJpcVI/AAAAAAAACF0/bef0oFEcb4E/s1600/device-2016-03-03-105200.png>
This would actually draw a black color for your canvas. See screenshot.
On Sunday, November 25, 2012 at 7:25:15 PM UTC-5, Romain Guy 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 <johan.w...@gmail.com <javascript:>
> > 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)
>>
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>
>
>
>
> --
> Romain Guy
> Android framework engineer
> roma...@android.com <javascript:>
>
>
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