How can I check whether dark mode is enabled in iO

Question

Starting from iOS/iPadOS 13, a dark user interface style is available, similar to the dark mode introduced in macOS Mojave. How can I check whether the user has enabled the system-wide dark mode?

Answer 1

1/ for UIView/UIViewController:

self.traitCollection.userInterfaceStyle == .dark

2/ for static or other:

UITraitCollection.current.userInterfaceStyle == .dark

BUT:

//Never use this! You will get wrong value in app extensions (ex. ToDay widget)
UIScreen.main.traitCollection.userInterfaceStyle == .dark //WRONG!

Answer 2

Create a class function for write method 1 time and use everywhere you want

class func isDarkMode()->Bool{
        if #available(iOS 12.0, *) {
            if UIScreen.main.traitCollection.userInterfaceStyle == .dark {
                return true
            } else {
                return false
            }
        } else {
           return false
        }
    }  

Answer 3

Objective C

To detect when dark mode is enabled or disabled via the Control Centre use an "appDidBecomeActive" notification that will be triggered when you return to your app.

//----------------------------------------------------------------------------
//                          viewWillAppear
//----------------------------------------------------------------------------
- (void)viewWillAppear {
    [super viewWillAppear];

    [[NSNotificationCenter defaultCenter]addObserver:self
                                   selector:@selector(appDidBecomeActive:)
                                   name:UIApplicationDidBecomeActiveNotification
                                   object:nil];

}

Don't forget to remove it when you're finished:

//------------------------------------------------------------------------------------
//                    viewWillDisappear
//------------------------------------------------------------------------------------
- (void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];

    [[NSNotificationCenter defaultCenter] removeObserver:self        
                                 name:UIApplicationDidBecomeActiveNotification 
                                 object:nil];

}

Do what ever you need to when dark mode changes:

//----------------------------------------------------------------------------
//                          appDidBecomeActive
//----------------------------------------------------------------------------
-(void)appDidBecomeActive:(NSNotification*)note {
    if (@available(iOS 13.0, *)) {
        if( self.traitCollection.userInterfaceStyle == UIUserInterfaceStyleDark ){
            //dark mode
        }
        else {
            //not dark mode
        }
    }
    else {
        //fall back for older versions
    }
}

Answer 4

You can use this extension:

import UIKit

extension UIApplication {
    @available(iOS 13.0, *)
    var userInterfaceStyle: UIUserInterfaceStyle? {
        return self.keyWindow?.traitCollection.userInterfaceStyle
    }
}

@available(iOS 13.0, *)
    func setSystemTheme() {
        switch UIApplication.shared.userInterfaceStyle {
        case .dark?:
            currentTheme = .dark
        case .light?:
            currentTheme = .light
        default:
            break
        }
    }

Answer 5

As mentioned by daveextreme, checking the current view user interface style doesn't always return the system style when you use the overrideUserInterfaceStyle property. In such cases it may be better to use the following code:

switch UIScreen.main.traitCollection.userInterfaceStyle {
case .light: //light mode
case .dark: //dark mode
case .unspecified: //the user interface style is not specified
}

Answer 6

You should check the userInterfaceStyle variable of UITraitCollection, same as on tvOS and macOS.

switch traitCollection.userInterfaceStyle {
case .light: //light mode
case .dark: //dark mode
case .unspecified: //the user interface style is not specified
}

You should use the traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) function of UIView/UIViewController to detect changes in the interface environment (including changes in the user interface style).

From Apple Developer Documentation:

The system calls this method when the iOS interface environment changes. Implement this method in view controllers and views, according to your app’s needs, to respond to such changes. For example, you might adjust the layout of the subviews of a view controller when an iPhone is rotated from portrait to landscape orientation. The default implementation of this method is empty.

System default UI elements (such as UITabBar or UISearchBar) automatically adapt to the new user interface style.