Dark Theme Settings
Dark theme (black background) is supported in Android 10 and later.
By default, it follows the system settings of the OS.
If you want to make your own settings, please go to
Settings > Dark Theme.
When the background is dark on Android 9 or earlier
If color inversion is set to ON in the OS system settings, the background of this app screen will also be black.
Please change the setting by going to
Settings App > Accessibility > Color Inversion.
For the Widget, follow the system settings of your OS.