android - What's the difference between windowBackground and background for activities style?

Question

I have a background set for all of the activities of the app by using the "android:background" parameter in the styles and setting the theme of the application to link to this style.

All worked well, till I've noticed that for a dialog with a list of items, it makes each item to have the full size of the background .

After changing the parameter being used to "android:windowBackground" it seems to work fine in this case too.

Why does it occur? What is the difference between the two?

Also , does setting "android:windowBackground" to @null as written here provide the same speed boost as using "android:background"?

Answer 1

android:background is the background color (drawable to be precise) of a view component whereas android:windowBackground is the background color of the window (activity or dialog) in which your view resides.

By default views are transparent (i.e. no background color) so visually it looks like they are taking the color from the underlying window.

Notice how the article you linked to mentions setting the windowBackground to null and not the background for fullscreen views. This is a common technique to avoid overdraws.

But the same principle can be applied to views if you have one view completely hide the other view.

Example: gist.github.com/floatingmonkey/5474959