I have a Xamarin Forms application and I am currently working on code for an iOS. In my settings I have an option to change the application's theme (Dark and Light). This basically just changes the background colors and text colors of the pages. Now what I want to do is to be able to change the SelectedImageTintColor and BarTintColor of the TabBar as well as the the BarTintColor and TintColor of the NavigationBar. At the moment I have create a renderer for the tabbed page:
protected override void OnElementChanged(VisualElementChangedEventArgs e) { base.OnElementChanged(e); App.theme = (Theme)App.DB.GetIntSetting("ThemeColor"); switch (App.theme) { case Theme.Dark: { TabBar.SelectedImageTintColor = UIColor.FromRGB(255, 165, 0); TabBar.BarTintColor = UIColor.Black; break; } case Theme.Light: { TabBar.SelectedImageTintColor = UIColor.FromRGB(60, 132, 60); TabBar.BarTintColor = UIColor.White; break; } } } Right now these colors would only take effect when you first start the application.
I researched this problem but could not find any answer from anyone on how to solve this problem.
I know there have been many changes to Xamarin so I would like to find out if there are any recent developments or new ways to tackle this problem. I am open to looking into any possible suggestions as part of the requirement for the application is to be able to change these colors.
Edits:
My Tabbed page was created like the following:
public partial class MainPage : TabbedPage { public MainPage() { InitializeComponent(); var phrasesPage = new NavigationPage(new PhrasesPage()) { Title = "Play", Icon = "play1.png" }; var settingsPage = new NavigationPage(new SettingsPage()) { Title = "Settings", Icon = "settings.png" }; // other declarations here Children.Add(phrasesPage); Children.Add(settingsPage); // and more } } For instance, if I choose Dark theme then the TabBar and NavigationBar background color would be black, the TabBar's selectedimage would be orange and the NavigationBar's text would be white. Likewise if I choose Light theme then the TabBar and NavigationBar background color would be white, the TabBar's selectedimage would be green and the NavigationBar's text would be black.
2 Answers
Answers 1
I think the problem is that you are not listening for and handling the theme change. You are setting the colors in OnElementChanged which is not going to be called again when you change the theme.
You can create a property that will fire off an event that you subscribe to in your custom renderer. For example, if you create the property in your App class then in your custom TabbedPage renderer you can do:
protected override void OnElementChanged(VisualElementChangedEventArgs e) { base.OnElementChanged(e); if(e.OldElement != null) { App.Current.PropertyChanged -= Current_PropertyChanged; return; } App.Current.PropertyChanged += Current_PropertyChanged; //subscribe to the App class' built in property changed event UpdateTheme(); } void Current_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e) { if(e.PropertyName == "DarkTheme") { UpdateTheme(); } } Since the navigation bar is controlled by the NavigationPage instead, you will have to listen for the property change there too. Fortunately you won't need a custom renderer since you can change the bar and text colors with Forms properties. So you can create a class that inherits from NavigationPage and subscribe to the event:
public class CustomNavigationPage : NavigationPage { public CustomNavigationPage(Page root) : base(root) { if(Device.OS == TargetPlatform.iOS) { App.Current.PropertyChanged += Current_PropertyChanged; } } } I created a sample project that demonstrates all of this so you can check it out :)
Answers 2
You can use tabbar's property to change background and icon color whenever you need to use.
TabBar.TintColor = UIColor.White; // changer as per your need for tab icon's color TabBar.BarTintColor = UIColor.Black; // changer as per your need for tabbar's backgroungcolor same as for navigation
this.NavigationController.NavigationBar.TintColor = UIColor.White;//change as per your need for tab icon color this.NavigationController.NavigationBar.BarTintColor = UIColor.Black;// changer as per your need for Navbar' backgroungcolor 
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