Set opacity to PictureDrawable

Question

I need a piece of advice with setting opacity to a PictureDrawable object since usual setAlpha() is not implemented in PictureDrawable. My case is pretty similar to this one (I also get my drawables from SVGs in raw resources using a library). But I cannot use the solution because I would like to change the opacity dynamically (not by applying color filter at creation).

The context is animating multiple drawables when drawing on a SurfaceView.

What could be a good workaround in this situation?

Thank you.

use Canvas.saveLayerAlpha, this method is used in pre v4 devices when drawing AlphaAnimations — pskink, Nov 21 '14 at 21:20

score 0 · Accepted Answer · edited May 23 '17 at 12:12

Credit goes to @pskink, I'll just elaborate it a little for further references. This is what I do in onDraw(Canvas canvas) method (in my case int opacity changes iteratively from 0 to 255):

int width = drawable.getIntrinsicWidth();
int height = drawable.getIntrinsicHeight();

canvas.saveLayerAlpha(x, y, x + width, y + height, opacity,
                                  Canvas.HAS_ALPHA_LAYER_SAVE_FLAG);

drawable.setBounds(x, y, x + width, y + height);
drawable.draw(canvas);
canvas.restore();

This answer also provides good guidance on saveLayerAlpha() usage.

Set opacity to PictureDrawable

1 Answers1