an Android emulator running Android Marshmallow or higher.

To be able to follow along, you'll need the following: In this quick tip, I'll be showing you how to use the framework to create a simple theme that changes the looks of the quick settings tray.

More specifically, by apps that are installed in a location that can be accessed only by the root user, or by someone who's creating a custom ROM. What's the catch, you ask? Well, the framework can be used only by privileged apps.

And the best part about it is that you don't have to write any Java code whatsoever. Because Android's system user interface components, including the navigation bar, the status bar, the notifications tray, and the quick settings tray, themselves belong to an app, you can change their looks too. With RRO, you can quickly create themes that can change the look and feel of almost every app that's installed on an Android device. It's called the Runtime Resource Overlay framework, RRO for short, and it dramatically reduces the effort needed to create custom themes for your phone.

Not many know about it, and Google rarely advertises it, but the Android operating system has had a theming framework built into it for a few years now.

Android studio theme framework .