如何更改颜色以调整 UWP 中的主题设置？

Question

Simply want to set Foreground color of a TextBlock to LightGreen in dark mode, set to DarkGreen in light mode. There is a theme setting in my app. I want the color adjust both system setting and app setting.

I tried this when page loaded:

var isDark = ThemeSelectorService.Theme == ElementTheme.Dark;
if(ThemeSelectorService.Theme == ElementTheme.Default)
{
   isDark = Application.Current.RequestedTheme == ApplicationTheme.Dark;
}
PriceText.Foreground = new SolidColorBrush(isDark ? Colors.LightGreen : Colors.DarkGreen);

<TextBlock x:Name="PriceText" Text="This is a Text"/>

but when I change the system setting, the color will not change until reload to this page, how to make it happen?

Answer 1

When system color changes, the page loaded method will not be called. You could use UISettings.ColorValuesChanged Event to monitor the changes of system color.

when I change the system setting, the color will not change until reload to this page

If you change the color of your app by changing the value of FrameworkElement.RequestedTheme property which can override the app-level RequestedTheme , you need to change the value of the FrameworkElement.RequestedTheme property to ElementTheme.Default to let the FrameworkElement.RequestedTheme use the Application.RequestedTheme without reloading the page.

Please check the following code to let the color adjust system setting:

public MainPage()
{
    this.InitializeComponent();
    ……
    uiSettings.ColorValuesChanged += UiSettings_ColorValuesChanged;
}

private async void UiSettings_ColorValuesChanged(UISettings sender, object args)
{
    var isDark=false;
    await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, () =>
    {
        //Change the RequestedTheme of elements to ElementTheme.Default
        // if you have changed some elements' RequestedTheme property
        RequestedTheme = ElementTheme.Default;
        ThemeSelectorService.Theme = ElementTheme.Default;

        isDark = Application.Current.RequestedTheme == ApplicationTheme.Dark;
        PriceText.Foreground = new SolidColorBrush(isDark ? Colors.Green : Colors.Red);
    });
}

Answer 2

Answer from YanGu

Step 1: add ResourceDictionary.ThemeDictionaries to ResourceDictionary

<ResourceDictionary.ThemeDictionaries>
    <ResourceDictionary x:Key="Light">
        <SolidColorBrush x:Key="PriceBrush" Color="DarkGreen"/>
    </ResourceDictionary>
    <ResourceDictionary x:Key="Dark">
        <SolidColorBrush x:Key="PriceBrush" Color="LightGreen"/>
    </ResourceDictionary>
</ResourceDictionary.ThemeDictionaries>

Step 2: use the SolidColorBrush for your usercontrol

<TextBlock Text="This is a text" Foreground="{ThemeResource PriceBrush}"/>

This is pretty easy but cannot be found in other questions.