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POInvalidate-like method for WallpaperServices' draw method
 

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  1. POInvalidate-like method for WallpaperServices' draw method
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    <p>I was trying to make moving bitmap with accelerometer smoother and accidentally noticed that when I call <code>invalidate();</code> at the end of <code>onDraw()</code> method instead of calling it at the end of <code>onSensorChanged()</code> I get much smoother movement, even if I don't have any kind of low-pass filters. Then I tried to do the same with my LiveWallpaper, but as you know there is no <code>onDraw()</code> method in <code>Engine</code> of <code>WallpaperService</code>, but you have to create one yourself and call it for example with <code>Handler</code>. But doing it that way doesn't give any smoother result even if the rest of the code is same as in other programs.</p> <p>This is the code that I use in my non-Wallpaper programs and it works fine:</p> <pre><code>public void onDraw(Canvas c) { xPosition += xAcceleration; yPosition += yAcceleration; drawable = BitmapFactory.decodeResource(getResources(),R.drawable.ball); c.drawBitmap(drawable, xPosition,yPosition, paint); invalidate(); } </code></pre> <p>So I went and tried to create my own invalidate-like solution for <code>WallpaperService</code> and came up with this:</p> <pre><code>void drawFrame() { final SurfaceHolder holder = getSurfaceHolder(); Canvas c = null; try { c = holder.lockCanvas(); if (c != null) { xPosition += xAcceleration; yPosition += yAcceleration; background = BitmapFactory.decodeResource(getResources(),R.drawable.bg); drawable = BitmapFactory.decodeResource(getResources(),R.drawable.ball); c.drawBitmap(background, 0,0, null); c.drawBitmap(drawable, xPosition,yPosition, null); } } catch (Exception ex){ } holder.unlockCanvasAndPost(c); drawFrame(); } </code></pre> <p>So what I am doing is:</p> <ol> <li>Get <code>Canvas</code>.</li> <li>Draw on <code>Canvas</code>.</li> <li>Unlock <code>Canvas</code> and start over.</li> </ol> <p>As I have understood this should give me <code>invalidate();</code>-like behaviour, but instead it tries to show wallpaper and after while it gives me StackOverflowError.</p>
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