Android - drawing cache - when is it useful?

Question

I am reading about setDrawingCacheEnabled and getDrawingCache and I was wondering when is it good to use it or when its not good.

Basically in my case I have an HorizontalScrollView with many things inside it so its scrolls left/right and most of the things are not visible.

If I use setDrawingCacheEnabled(true) on the views, does it help? or this is only when I use custom views and I call getDrawingCache()?

Is there any other 'cache' way to use in a HorizontalScrollView?

Answer 1

TouchInterceptor.java - This is class responsible for reordering your playlist in the default music player. It uses setDrawingCacheEnabled when you start dragging the current view. Basically, it creates a bitmap from the ListView item and drag it. Take a closer look at onInterceptTouchEvent method.

Answer 2

It's definitely useful for screenshots as Marcel said. It is also very useful performance-wise, as that is what it was created for. It does use up more memory, as you render the view into a bitmap first.

What you do is, you setDrawingCacheEnabled to true, call getDrawingCache which returns a bitmap and store this bitmap. In onDraw, you do draw the bitmap you got if the cache is on, or the view otherwise. This can be very nice when scrolling.