Android: Drawing a bitmap on a hardware-accelerated canvas yields corrupted display, odd behavior

Question

I've been stuck for several days on drawing to a hardware-accelerated canvas from a live wallpaper.

When the wallpaper launches, it's in portrait mode and everything initially looks OK: HW canvas: upright

When I rotate the phone, the left half of the screen contains the image and the right half of the screen is black: HW canvas: rotated

Then, when I rotate back to the original orientation, it gets weirder. HW canvas: back to upright

Drawing on a non-accelerated canvas works fine. Just change lockHardwareCanvas in the code below to lockCanvas. Software canvas: upright - Software canvas: rotated

Sample code:

package reproduceproblem

import android.graphics.Bitmap
import android.graphics.BitmapFactory
import android.graphics.Canvas
import android.graphics.Rect
import android.service.wallpaper.WallpaperService
import android.util.DisplayMetrics
import android.view.SurfaceHolder
import android.view.WindowManager

class MyWallpaperService: WallpaperService() {
   override fun onCreateEngine(): Engine = WallpaperEngine()

   inner class WallpaperEngine : WallpaperService.Engine() {
      override fun onSurfaceChanged(
         holder: SurfaceHolder,
         format: Int,
         width: Int,
         height: Int
      ) {
         super.onSurfaceChanged(holder, format, width, height)

         val bmp: Bitmap = BitmapFactory.decodeResource(applicationContext.resources, R.drawable.webb)
         val rect = Rect( 0, 0, width, height )
         val canvas: Canvas = holder.lockHardwareCanvas()

         canvas.drawBitmap(bmp, null, rect, null)
         holder.unlockCanvasAndPost(canvas)
      }
   }
}

Try to draw on the method onSurfaceRedrawNeeded – Style-7 Oct 21 '22 at 06:45 — Style-7, Oct 21 '22 at 06:45

score 0 · Answer 1 · answered Apr 16 '22 at 21:18

0

I never figured out why this was happening, but I solved it very quickly by using libgdx. Make sure to create a new SpriteBatch on device rotation, because SpriteBatch internally sets its own width and height, and it doesn't update once created.

answered Apr 16 '22 at 21:18

protochicken

1
2

As it’s currently written, your answer is unclear. Please [edit] to add additional details that will help others understand how this addresses the question asked. You can find more information on how to write good answers [in the help center](/help/how-to-answer). – Community Apr 17 '22 at 00:28

Android: Drawing a bitmap on a hardware-accelerated canvas yields corrupted display, odd behavior

1 Answers1