使用 PixelCopy.request() 保存 SurfaceView 的屏幕截图返回黑色 bitmap

Question

I'm developing an app where I need to save the content drawn on a SurfaceView canvas to an image file. I read that the PixelCopy API can be used to do this after API level 24, but so far my code only returns an empty, black bitmap.

Here's what I tried:

private CustomView my_view; //CustomView extends SurfaceView implements SurfaceHolder.Callback

private void captureImage()
{
  Bitmap bitmap = Bitmap.createBitmap(my_view.getWidth(), my_view.getHeight(), Bitmap.Config.ARGB_8888);

  PixelCopy.request(my_view, bitmap, new PixelCopy.OnPixelCopyFinishedListener() {
      @Override
      public void onPixelCopyFinished(int copyResult) 
      {
        try {
           saveImageToFile(bitmap, "myfilename"); //This saved image is empty and black
        } 
        catch (IOException ignored) {
        }
      }
    }, new Handler(Looper.getMainLooper()));
}

If I try the old approach of using getDrawingCache() as shown below, then everything works as expected and I get an image with all the content rendered on the SurfaceView.

my_view.setDrawingCacheEnabled(true);
Bitmap bitmap = my_view.getDrawingCache(); //This works
try {
  saveImageToFile(bitmap, "myfilename");
} 
catch (IOException ignored) {
}
my_view.destroyDrawingCache();
my_view.setDrawingCacheEnabled(false);

However, I would like to use the PixelCopy API since the getDrawingCache() function has been deprecated. Does anyone know what the issue might be with my PixelCopy approach above?

Answer 1

Have you checked the copyResult if it is success? I recently used PixelCopy , and it worked very well. I will provide the code.

First we get the view coordinates on the window as a Rect :

fun getViewRect(screenshotView: View): Rect {
    val viewPadding = 8.toIntPixel(this)

    val viewLocation = IntArray(2)
    screenshotView.getLocationInWindow(viewLocation)

    return Rect(
        viewLocation[0] - viewPadding,
        viewLocation[1] - viewPadding,
        viewLocation[0] + screenshotView.width + viewPadding,
        viewLocation[1] + screenshotView.height + viewPadding
    )
}

then we write a function to take a screenshot:

fun takeScreenshot(
    activity: Activity,
    viewRect: Rect,
    onSuccess: (Bitmap) -> Unit
) {
    val bitmap = Bitmap.createBitmap(viewRect.width(), viewRect.height(), Bitmap.Config.ARGB_8888)
    PixelCopy.request(activity.window, viewRect, bitmap, 
        { copyResult ->
            if (copyResult == PixelCopy.SUCCESS) {
                onSuccess(bitmap)
            } else {
                error("problem with taking a screenshot")
            }
            bitmap.recycle()
        },
        Handler(Looper.getMainLooper())
    )
}

then you can call the function:

takeScreenshot(activity, activity.getViewRect()) { bitmap ->
    saveImageToFile(bitmap, "myfilename.png")
}