Why setting a layout background with shape drawable causes a warning on Android Studio 1.4 telling that cannot set background in RelativeLayout?
Android Studio warning about invalid background:

Drawable shape used as background:

Nothing to be concerned about. It is an android studio problem, it normally shows a preview icon of the drawable, but in this case it cannot show a preview of a drawable XML and shows that "error"
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With