view - Android drawing cache

Question

Please explain how does the drawing cache work in Android. I'm implementing a custom View subclass. I want my drawing to be cached by the system. In the View constructor, I call

setDrawingCacheEnabled(true);

Then in the draw(Canvas c), I do:

    Bitmap cac = getDrawingCache();
    if(cac != null)
    {
        c.drawBitmap(cac, 0, 0, new Paint());
        return;
    }

Yet the getDrawingCache() returns null to me. My draw() is not called neither from setDrawingCacheEnabled(), nor from getDrawingCache(). Please, what am I doing wrong?

Answer 1

There's a hard limit on drawing cache size, available via the ViewConfiguration class.. My view is larger than allowed for caching.

FYI, the sources of the View class are available via the SDK Manager for some (not all) Android versions.