Use qualifiers in image file names does not work in UWP runtime

Question

I was trying to change image for Theme/HighContrast change in UWP app. I followed the link: tailor-resources-lang-scale-contrast But it is not working when I change theme while app is running. It works after app restarting. I followed folder name qualifiers & file name qualifiers both. Do I need to do any additional changes? Can anyone please help me?

Answer 1

Hello,

Welcome to Microsoft Q&A!

Based on this document, it mentions you need to subscribe the MapChanged event on ResourceContext.QualifierValues to respond to changes in system settings. When your HighContrast changes, this event will be triggered, then you can reload your images with the help of the default ResourceContext. For example:

.cs:

public MainPage()  
{  
    this.InitializeComponent();  

      
    // Subscribe to the event that's raised when a qualifier value changes.  
    var qualifierValues = Windows.ApplicationModel.Resources.Core.ResourceContext.GetForCurrentView().QualifierValues;  
    qualifierValues.MapChanged += new Windows.Foundation.Collections.MapChangedEventHandler<string, string>(QualifierValues_MapChanged);  
}  

private async void QualifierValues_MapChanged(IObservableMap<string, string> sender, IMapChangedEventArgs<string> @event)  
{  
    var dispatcher = this.myImageXAMLElement.Dispatcher;  
    if (dispatcher.HasThreadAccess)  
    {  
        this.RefreshUIImages();  
    }  
    else  
    {  
        await dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, () => this.RefreshUIImages());  
    }  
}  

private void RefreshUIImages()  
{  
    //The folder naming: \Assets\Images\contrast-standard\1.jpg  
    var namedResource = Windows.ApplicationModel.Resources.Core.ResourceManager.Current.MainResourceMap[@"Files/Assets/Images/1.jpg"];  
    this.myImageXAMLElement.Source = new Windows.UI.Xaml.Media.Imaging.BitmapImage(namedResource.Uri);  
}