Canvas.DrawBitmap holds reference to bitmap

Asked Oct 30 '16 at 10:48

Active Oct 30 '16 at 14:35

Viewed 90 times

In the following function:

protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    canvas.drawBitmap( bmp ,0,0,null);
    ViewCompat.postOnAnimationDelayed( this, new Runnable() {
        @Override
        public void run() {
            Canvas c = new Canvas(bmp);
            c.drawColor(Color.BLUE);
        }
    },1000);
}

bmp is a regular image.

I am drawing the bitmap on the canvas.
On the next animation frame + 1 sec, I'm changing the content of the bitmap to blue.
I'm NOT drawing the bitmap again.

The result is a blue screen.

Does this mean that the canvas is storing a reference to the bitmap?

edited Oct 30 '16 at 14:35

Carlos Vázquez Losada

asked Oct 30 '16 at 10:48

user7091237

turn off hardware acceleration – pskink Oct 30 '16 at 11:04
Hi pskink, 10x for your reply. I need the hardware acceleration but i will try and update. – user7091237 Oct 30 '16 at 11:42
Ok its working. disable hardware acceleration indeed solve the problem. However, as i said, i need the hardware acceleration so will have to find another solution. Thanks. – user7091237 Oct 30 '16 at 14:00
what actually do you want to achieve by your code? – pskink Oct 30 '16 at 14:13
i thought that on the next frame the bitmap already drawn so i can now use it for other purposes. for example, to prepare and draw it on other cells on grid. – user7091237 Nov 01 '16 at 14:10
so you need another Bitmap for that – pskink Nov 01 '16 at 14:12
that what i wanted to avoid, the creation of another bitmap. – user7091237 Nov 01 '16 at 14:21
so just call `Canvas#drawColor(Color.BLUE);` you dont need a `Bitmap` for that – pskink Nov 01 '16 at 14:24
it was just an example to show that changes in the bitmap affect the view even after the draw bitmap. assume that the same bitmap is being used to resize an image and draw it on another view. still, the first view will be affected also. – user7091237 Nov 01 '16 at 14:47

Canvas.DrawBitmap holds reference to bitmap

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