I recently made the switch to Android Studio as my default IDE for Android development. When designing my UI I normally use the palette in the design view to assist in arran
Open Activity XML file Then Click the design View Or Windows->
You must have something in the layout resource highlighted. I also had to compile without an error.
Right click on the .xml file tab. Select "split vertically". This will open another Design that shows the palette again.
First Close All The Tabs Then Open res->layout->activity_main.xml you will able to see design tab at activity_main.xml
I've just figured this out! If you double click on your .xml file tab at the top it will maximize the designer window. Then on the left you can drag the window to shrink and it will reveal the palette. Then just click on the tab on the left to open the project window.
try the Design/Text tabs in the lower left of the layout window