无法更改materialdesigninxaml的重音

Question

I'm trying to add the MaterialDesign accents to a MenuItem, actually I've managed this partially, this is what I did so far:

Menu creation:

 <Menu Grid.Row="0" HorizontalAlignment="Left" VerticalAlignment="Stretch">
            <MenuItem Header="Stile" Width="100" 
                      ItemContainerStyle="{StaticResource AccentColorMenuItemStyle}"
                      ItemsSource="{Binding SettingsController.Swatches, Mode=OneWay}" />
 </Menu>

container definition:

 <Ellipse x:Key="AccentMenuIcon"
                 Width="16"
                 Height="16"
                 x:Shared="False"
                 Fill="{Binding AccentExemplarHue.Color, Converter={StaticResource ColorToBrushConverter}, Mode=OneWay}" />

    <Style x:Key="AccentColorMenuItemStyle"
           BasedOn="{StaticResource MetroMenuItem}" TargetType="{x:Type MenuItem}">
        <Setter Property="Command" Value="{Binding DataContext.ApplyAccentCommand, 
            RelativeSource={RelativeSource AncestorType=Window}}" />
        <Setter Property="Header" Value="{Binding Name, Mode=OneWay}" />
        <Setter Property="Icon" Value="{StaticResource AccentMenuIcon}" />
    </Style>

I defined a Color converter to display as Ellipse color:

public class ColorToBrushConverter : IValueConverter 
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return new SolidColorBrush((Color)value);
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        SolidColorBrush c = (SolidColorBrush)value;
        System.Drawing.Color col = System.Drawing.Color.FromArgb(c.Color.A, c.Color.R, c.Color.G, c.Color.B);
        return col;
    }
}

then in my viewmodel I've implemented in this way:

    private static void ApplyBase(bool isDark)
    {
        new PaletteHelper().SetLightDark(isDark);
    }

    public IEnumerable<Swatch> Swatches { get; }

    public ICommand ApplyPrimaryCommand { get; } = new SimpleCommand(o => ApplyPrimary((Swatch)o));

    private static void ApplyPrimary(Swatch swatch)
    {
        new PaletteHelper().ReplacePrimaryColor(swatch);
    }

    public ICommand ApplyAccentCommand { get; } = new SimpleCommand(o => ApplyAccent((Swatch)o));

    private static void ApplyAccent(Swatch swatch)
    {
        new PaletteHelper().ReplaceAccentColor(swatch);
    }

with the code above I get all the accents displayed in the menuItem, but I've a problem, when

I click on the menuItem color, and the Command "ApplyAccentCommand" is called I get a null exception here:

private static void ApplyAccent(Swatch swatch)
{
    new PaletteHelper().ReplaceAccentColor(swatch);
}

in particular on the swatch object (that's the accent) what I did wrong? Thanks.

Answer 1

I suspect you are actually getting an ArgumentNullException. Since the ReplaceAccentColor checks the incoming parameter for null . If you set a break point on that line I suspect that swatch is null.

I see that you are setting up the command, but not setting up the command's parameter meaning that the default value of null will be used.

Simply adding one more setter to your menu item style should fix it.

<Setter Property="CommandParameter" Value="{Binding}" />