android-discuss, want to draw over a changing solid-color background

by **Rob Y.** » Fri, 23 Apr 2010 10:56:32 GMT

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 I'm trying to draw an animated picture over a background that I want
to shift gradually in color.

The picture is kept in a bitmap, and on each frame, I erase the
background to the new background color and then draw the bitmap on top
of it.  The bitmap was originally cleared to Color.TRANSPARENT, and
that works.  I can see the background color.  But as I animate my
image, each pixel in the bitmap that I 'erase' to Color.TRANSPARENT
seems to remain whatever color it originally was.  Eventually I just
end up with a big blob of color where the moving image should be.

Am I doing something wrong?  How come Color.TRANSPARENT results in
transparency when I use it to drawColor to my bitmap canvas, but not
when I draw with a Color.TRANSPARENT paint to the same canvas?

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