How to toggle Android Q’s hidden system-wide dark theme

Earlier today, Google released the first Android Q beta for all three generations of Pixel devices: the Google Pixel/Pixel XL, Pixel 2/Pixel 2 XL, and Pixel 3/Pixel 3 XL. This is the first of 6 betas we’ll get before the final release, and there’s a ton of new features. Google published lots of documentation for the new Android version, and it’ll take us some time to go through it all. I flashed the Q beta on the Pixel 3 XL to find any new features that haven’t been covered by our leaks, and to be honest, there aren’t that many user-facing features in the beta that we haven’t uncovered yet. One major feature—Android Q’s system-wide dark mode—is mysteriously missing for many people, though.

Some people updated to Q with it enabled, while others (like me) updated without any way to enable it in Settings. You can enable the system-wide dark theme by turning on battery saver, but battery saver isn’t something you’ll want to keep enabled if you rely on getting notifications on time. Since people updated from Android Pie to Android Q with the dark theme already enabled, that got me thinking: How did that happen? I concluded that these users must have had the forced night mode setting enabled in Developer Options prior to upgrading to Q. That setting has disappeared from the Q beta, but it’s still possible to enable it manually with ADB. Here’s how.

Toggle Android Q’s Hidden Dark Mode

1. 1. Follow this tutorial to enable the use of ADB from your PC.
   2. Plug in your Pixel to your PC, open a command prompt or terminal window in the same directory where you stored the ADB binary, and enter the following command:
      Enable Dark Mode: adb shell settings put secure ui_night_mode 2
      Disable Dark Mode: adb shell settings put secure ui_night_mode 1
   3. If you’re using Windows PowerShell, then you may need to add a .\ before the command. If you’re using macOS or Linux, then you may need to add a ./ before the command.
   4. Reboot your Pixel and the system-wide dark mode should be toggled.

I’m not entirely sure why Google removed access to dark mode in the Android Q beta. The most likely explanation is that it’s still in development. I hope that it gets enabled in a future beta because developers will need time to test their apps. For some reason, this toggle not only enables dark mode in Settings, SystemUI, and the framework, but it also forces dark mode in all apps which looks terrible in Google Photos. In the leaked Android Q beta, I was able to enable dark mode for system apps but keep the forced dark mode disabled—that doesn’t seem possible here. I’m still investigating whether that’s possible, but I believe we’ll need root access because the flag is tied to the system property debug.hwui.force_dark.

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Refference - xdadevelopers.com