Changing background image based on localsettings

问题

I define every page background in App.xaml, like this:

<Application.Resources>
    <ResourceDictionary>
        <ResourceDictionary.ThemeDictionaries>
            <ResourceDictionary x:Key="Default">
                <ImageBrush x:Key="BackgroundImage" ImageSource="Assets/Background.png" Stretch="UniformToFill" />
            </ResourceDictionary>
        </ResourceDictionary.ThemeDictionaries>
    </ResourceDictionary>
</Application.Resources>

And now I wish to change the background image if the user select another theme, for example:

if(localSettings.Values["theme"].ToString() == "Dark"){
    //set ImageSource="Assets/BackgroundDark.png"
}

How can I do?

回答1:

Have you tried this defining Dark option in ThemeResource which would be used based on System theme?

<Application.Resources>
    <ResourceDictionary>
        <ResourceDictionary.ThemeDictionaries>
            <ResourceDictionary x:Key="Default">
                <ImageBrush x:Key="BackgroundImage" ImageSource="Assets/Background.png" Stretch="UniformToFill" />
            </ResourceDictionary>
            <ResourceDictionary x:Key="Dark">
                <ImageBrush x:Key="BackgroundImage" ImageSource="Assets/BackgroundDark.png" Stretch="UniformToFill" />
            </ResourceDictionary>
        </ResourceDictionary.ThemeDictionaries>
    </ResourceDictionary>
</Application.Resources>

EDIT: If you're looking to change the value based on some custom local setting value, you might want to try this:

BitmapImage darkImage = new BitmapImage(new Uri("Assets/BackgroundDark.png", UriKind.Relative));
(App.Current.Resources["BackgroundImage"] as ImageBrush).ImageSource = darkImage;

// or page Resources, depending on where the resource dictionaries are defined
// (this.Resources["BackgroundImage"] as ImageBrush).ImageSource = darkImage;

回答2:

If you simply want to select na image according to the current theme, you can use the "theme" qualifier.

In your case, you can maintain the image's path to "Assets/Background.png" and on that directory have "Assets/Background.theme-dark.png" and "Assets/Background.theme-light.png". Each one will be selected according to the current theme being used. Programmatically you can check it just by calling:

App.Current.RequestedTheme

来源：https://stackoverflow.com/questions/24326363/changing-background-image-based-on-localsettings

标签

xaml

winrt-xaml

windows-phone-8.1