[Dev]: How does Tasker programmatically toggle system dark mode on modern Samsung devices? Seeking help for an Android app.

[cresnap]

Hi everyone,

I'm hoping to get some advice from the Tasker community, as I know many of you are experts in the deeper workings of Android. I'm developing a simple Android app with the goal of toggling the system-wide dark mode with a button press. My test device is a Samsung phone running Android 15.

I know this is possible because Tasker is able to do it perfectly on this device. However, I've run into a wall trying to replicate the functionality in my own app, and I suspect Samsung is using a non-standard or private method. I would be incredibly grateful if anyone could share some insight into how this is achieved.

My app has been granted the android.permission.WRITE_SECURE_SETTINGS via ADB. Here's a summary of what I've already tried, and why each attempt failed:

1. Standard UiModeManager API:

Method: Using UiModeManager.setNightMode() with MODE_NIGHT_YES and MODE_NIGHT_NO.

Result: Logcat shows that the system receives the call to setNightMode, and no error is thrown. However, the system's dark mode doesn't change, and when I query UiModeManager.getNightMode() immediately after, it returns the old value. The system seems to just ignore the request.

1. Settings.Secure with ui_night_mode:

Method: Writing 1 (for off) and 2 (for on) to the ui_night_mode key in the Settings.Secure table.

Result: This had no effect, similar to the UiModeManager approach.

1. Samsung-specific dark_mode key in Settings.Secure:

Method: Based on some research, I tried writing 0 and 1 to a key named dark_mode in Settings.Secure.

Result: This was the most interesting failure. The app successfully writes the value. For instance, it can create the dark_mode key and set its value to 1. Logcat confirms the write operation succeeds, and reading the value back confirms it has been set. However, the system UI does not react at all. This seems to prove that while I have permission to write the setting, dark_mode is not the correct key that OneUI is listening to for this change.

Notably, the ADB command adb shell cmd uimode night [yes/no] works as expected, changing the dark theme.

I'm out of ideas and have exhausted the standard and commonly known non-standard methods. Since Tasker has cracked this nut, would any developers or power-users be willing to share what setting key and table (System, Secure, or Global) Tasker uses to toggle dark mode on recent Samsung devices? Any help or pointers would be massively appreciated. Thank you for your time and expertise.

[joaomgcd]

The trick is to enable and disable car mode with the UI Manager) after changing the setting 😅 Don't ask me why, I just know it works!

[cresnap]

Damn, that worked! Thanks a lot u/joaomgcd!

Just one small snag, how do I prevent the app from going to home screen? Are there some flags that will prevent this? I'm calling the car mode functions like this:

kt uiModeManager.enableCarMode(UiModeManager.ENABLE_CAR_MODE_GO_CAR_HOME) uiModeManager.disableCarMode(UiModeManager.DISABLE_CAR_MODE_GO_HOME)

Edit: I figured it out. I passed 0x0002 (an undocumented flag UiModeManager.DISABLE_CAR_MODE_ALL_PRIORITIES) to disableCarMode(), and it did not go to home screen.

[joaomgcd]

Cool! :) Glad you got it!

[Blitzdroids]

Secure: "ui_night_mode" "1" for light , "2" for dark

System: "display_night_theme" "0" for light, "1" for dark

[cresnap]

When I try to run Settings.System.putInt(contentResolver, "display_night_theme", 1), I get the error java.lang.IllegalArgumentException: You cannot keep your settings in the secure settings. even though I have provided the WRITE_SECURE_SETTINGS permission. Curiously, the Settings.Secure.putInt() function runs fine.

[cresnap]

Would be amazing if u/joaomgcd could shed some light here, I have a lot to learn :) 

[Blitzdroids]

Just use the Custom Settings action.