Android - How to detect if night mode is on when using AppCompatDelegate.MODE_NIGHT_AUTO

If you are kotlin developer then you can use below code to judge dark mode.

when (context.resources?.configuration?.uiMode?.and(Configuration.UI_MODE_NIGHT_MASK)) {
    Configuration.UI_MODE_NIGHT_YES -> {}
    Configuration.UI_MODE_NIGHT_NO -> {}
    Configuration.UI_MODE_NIGHT_UNDEFINED -> {}
}

For more about dark theme mode

https://github.com/android/user-interface-samples/tree/main/DarkTheme

A very simple solution is to add a string resource like this.

res/values/strings.xml

<string name="mode">Day</string>

res/values-night/strings.xml

<string name="mode">Night</string>

And then wherever you need to check it:

if (resources.getString(R.string.mode) == "Day") {
    // Do Day stuff here
} else {
    // Do night stuff here
}

But you CAN NOT call this before super.onCreate() in an activity's life-cycle. It will always return "Day" before onCreate.

The bitwise operator in Java (which is used in @ephemient 's answer) is different in kotlin so the code might not be easily convertible for beginners. Here is the kotlin version just in case someone needs it:

    private fun isUsingNightModeResources(): Boolean {
        return when (resources.configuration.uiMode and 
Configuration.UI_MODE_NIGHT_MASK) {
            Configuration.UI_MODE_NIGHT_YES -> true
            Configuration.UI_MODE_NIGHT_NO -> false
            Configuration.UI_MODE_NIGHT_UNDEFINED -> false
            else -> false
    }
}

to check for night mode you can do as below:

public boolean isNightMode(Context context) {
    int nightModeFlags = context.getResources().getConfiguration().uiMode & Configuration.UI_MODE_NIGHT_MASK;
    return nightModeFlags == Configuration.UI_MODE_NIGHT_YES;
}

Kotlin Version :->

fun isDarkMode(context: Context): Boolean {
    val darkModeFlag = context.resources.configuration.uiMode and Configuration.UI_MODE_NIGHT_MASK
    return darkModeFlag == Configuration.UI_MODE_NIGHT_YES
}

For Xamarin.Android

if (Build.VERSION.SdkInt >= BuildVersionCodes.Froyo)
{
    var uiModeFlags = Application.Context.Resources.Configuration.UiMode & UiMode.NightMask;
    switch (uiModeFlags)
    {
        case UiMode.NightYes:
            // dark mode
            break;
        case UiMode.NightNo:
            // default mode
            break;
        default:
            // default mode
            break;
    }
}
else
{
// default mode
}

Maybe just a property that will actually tell you if you have Dark Mode ?

val Context.isDarkMode
    get() = if (getDefaultNightMode() == MODE_NIGHT_FOLLOW_SYSTEM)
        resources.configuration.uiMode and UI_MODE_NIGHT_MASK == UI_MODE_NIGHT_YES
    else getDefaultNightMode() == MODE_NIGHT_YES

From Android Version R (30) there is provided a value in context.resources.configuration.isNightModeActive.

So you don't need to mask anymore.

Example in onConfigurationChanged:

private var _isNightModeActive: Boolean = false

override fun onConfigurationChanged(newConfig: Configuration) {
        _isNightModeActive =
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
                _resources.configuration.isNightModeActive
            } else {
                newConfig.uiMode and
                        Configuration.UI_MODE_NIGHT_MASK ==
                        Configuration.UI_MODE_NIGHT_YES
            }
    }

I had problems with my UI tests, when try to get current theme in every answer code. It every time return the same value.

So I create static variable in application class and get theme for UI tests throw it:

@Theme
fun Context.getAppTheme(): Int? {
    val theme = when (resources.configuration.uiMode and Configuration.UI_MODE_NIGHT_MASK) {
        Configuration.UI_MODE_NIGHT_NO -> Theme.LIGHT
        Configuration.UI_MODE_NIGHT_YES -> Theme.DARK
        else -> null
    }

    Application.theme = theme

    return theme
}

In Application class:

companion object {
    @Theme
    @RunNone var theme: Int? = null
}

May be it will be usefull for someone!

I found nothing of this to be working after changing the the app to dark theme with

AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_YES);

Is there any way to know the system setting after changing the app with this method?
Thanks,
FF