With Android 9.0 Pie a standard function has finally been added to the settings where you can adjust the design of the status bar and various other areas such as the volume control.
The language is the so called "dark theme" or dark layout. By default the Android status bar is white. But this has annoyed many users, especially if you have a black or dark background.
With Android 9.0 Pie it is now possible to change the color of the status bar as follows:
Android 9.0 Pie - Customize Dark Theme for Status Bar etc.
1. Make sure you are using the latest version of Android Pie
2. Now open the settings and then the submenu "Display"
3. Then navigate to "Advanced" and then to "Devices Theme"
4. You now have the following options available: Automatically Light Dark
5. Set the marker to "Dark" to use the theme for your Android smartphone.
You now know how to set a dark theme in Android.