Android :: SurfaceHolder.unlockCanvasAndPost() Does Not Cause Redraw
Sep 29, 2010
I'm implementing a fairly standard app with the Android sdk that involves drawing using the SurfaceView, SurfaceHolder, Callback setup.
In my main thread (UI thread) I have no drawing or handling of the SurfaceHolder (or the canvas you retrieve with it).
In a separate thread I have the following:
CODE:...............
This code is being executed, throws no exceptions, and has no negative side effects that I can find; however, the unlockCanvasAndPost() call never causes onDraw() to be called.
In other words, unlockCanvasAndPost() does not cause a redraw of the SurfaceView.
Any ideas what could cause this symptom? I have plenty of java experience, a fair amount of android experience, and a lot of debugging experience and cannot track this one down.
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Apr 14, 2009
I am working on a game for Android. I'm following the general program layout of Lunar Lander, where a SurfaceView has a worker thread that runs the main game loop. That loop updates the physics and redraws the screen by creating and drawing to a canvas.
From the thread class:
CODE:.........
I believe surfaceHolder.unlockCanvasAndPost(canvas); is supposed to release the canvas and force the screen to redraw correct? That's not what I'm seeing. I'm getting strange behavior where the final draw works, but each previous draw only shows a black screen.
For a better example: I draw a small character sprite at the left side of the screen. Then, for each successive frame of 100 frames I translate the image one to the right. So I expect to see the sprite slide to the right as the program runs. Instead, the screen is black the whole time until the end, when the sprite appears already on the right side of the screen. It's as if the very last call to unlockCanvasAndPost() is applied to the screen, but the others are hidden or not drawn. I've verified that they are, in deed, being executed.
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Jul 19, 2010
I have an app which uses the Camera, sending the preview to a SurfaceHolder. Everything works fine on the HTC Desire that I have been developing on, but when I run it on a Samsung Galaxy S the image from the preview is rotated 90 degrees.
The code attempts to match the best Size returned from the parameters.getSupportedPreviewSizes(), with the width and height of the Surface (as passed into SurfaceChanged as width and height).
(the image is also rotated on the Galaxy when an image is taken from the app). Has anyone else had problems with the preview on the Galaxy? Or better yet got around the problems?
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Sep 17, 2010
I am developing the application which displays Video on the SurfaceHolder. When i run my video it plays well. But if i switch my application using "Home key", & go to some other application. Now if i come back by long Home key press to my application, my video does not get displayed but audio continues.
This happens because, onPause() is called for Activity when Application is switched. Thus the "SurfaceHolder" is destroyed, & next time no video is displayed.
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Jul 29, 2009
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Jun 1, 2010
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Currently the view is very simple, but I plan to add a bit more nice graphics. Since the whole keyboard is dynamically rendered this would make redrawing the entire keyboard more expensive.
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Am I wrong in expecting that calling invalidate(Rect dirty) would "cache" the current canvas, and only "allows" drawing in the dirty region?
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CODE:.................
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CODE:............
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