Android Studio Project Encoding Error

When you get that warning, click on Open File Encoding Settings. Then change both IDE Encoding and Project Encoding to UTF-8 from the select box. You can also change the default encoding at the bottom of the settings menu.

In your Android Studio open File >> Settings >> Editor >> File Encodings

And then set IDE Encoding, Project Encoding and Default encoding for properties file to UTF-8 as shown in the image below.