Can not apply style written in c#

Question

Hello, i have created style in C# code and tried to apply this style to the frame, named ControlsGroupMainFrame4 (written in XAML). Tried both WinUI and Android apps. Both apps do not throw any error and start fine, but the style is not applied.

Style is in separate class (in separate file):

(By the way, do i need to make this class static?)

public static class MyStyles
{
    static double screenWidthInDips;
    static Style ControlsGroupMainFrameStyle = new Style(typeof(Frame));
    public static Style GetControlsGroupMainFrameStyle()
    {
        MainThread.BeginInvokeOnMainThread(() =>
        {
            //get screen width in device-independent Units (DIPs)
            DisplayInfo mainDisplayInfo = DeviceDisplay.MainDisplayInfo;
            double screenWidth = mainDisplayInfo.Width; // in pixels
            double density = mainDisplayInfo.Density; // density factor
            screenWidthInDips = screenWidth / density; //screen width in device-independent Units (DIPs)
                                                       //System.Diagnostics.Debug.WriteLine("AAAAAAAAAAAAAAAAAAAAAAA" + screenWidthInDips);///////////////////////////ISTRINTI
            //set style for the frame
            Frame _Frame = new Frame
            {
                BorderColor = Color.FromArgb("#4c4c4c"),
                Margin = new Thickness(0, 0, 0, 5),
                BackgroundColor = (Color)Application.Current.Resources["BackgroundLightGreen"],
                Padding = 0,
                CornerRadius = 5,
                HasShadow = true
            };
            if (screenWidthInDips < 760) { _Frame.HorizontalOptions = LayoutOptions.Fill; } else { _Frame.HorizontalOptions = LayoutOptions.FillAndExpand; };
            if (screenWidthInDips < 760) { _Frame.WidthRequest = -1; } else { _Frame.WidthRequest = 360; };
            if (screenWidthInDips < 760) { _Frame.MinimumWidthRequest = -1; } else { _Frame.MinimumWidthRequest = 360; };
            //assign MyFrame style to the ControlsGroupMainFrame
            ControlsGroupMainFrameStyle = _Frame.Style;
        });
        //return style
        return ControlsGroupMainFrameStyle;
    }
}

Next i try to apply this style to the Frame:

public partial class ConnectionAndUpdate : ContentPage
{
public ConnectionAndUpdate()
{
    InitializeComponent();
    ControlsGroupMainFrame4.Style = MyStyles.GetControlsGroupMainFrameStyle();
}
}

The Frame in the XAML file:

<?xml version="1.0" encoding="utf-8" ?>
    <ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
                 xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
                 BackgroundColor="{StaticResource BackgroundDarkGreen}"
                 x:Class="AngryFish.PagesStandard.ConnectionAndUpdate"
                 xmlns:controls="clr-namespace:AngryFish.MyTemplates"
                 Title="Connection and update">
<Frame x:Name="ControlsGroupMainFrame4">
  <StackLayout Style="{StaticResource ControlsGroupMainLayout}">
    <Frame Style="{StaticResource ControlsGroupHeaderFrame}">
      <Label
          Style="{StaticResource ControlsGroupHeaderText}"
          Text="Help"/>
    </Frame>
    <StackLayout Style="{StaticResource ControlsGroupContentLayout}">
      <!--Code in the controls group starts here-->
      <StackLayout
          Orientation="Horizontal">
        <Label
            Style="{StaticResource StandardLabel}"
            Text="Get controller manual online:"/>
        <Image
            x:Name="ImageBook"
            Margin="5,0,0,0"
            Source="other_book_symbol.png"
            Aspect="AspectFit"
            HeightRequest="40"
            HorizontalOptions="Start"/>
      </StackLayout>
      <!--Code in the controls group ends here-->
    </StackLayout>
  </StackLayout>
</Frame>
</ContentPage>

Answer 1

Hello,

You new a frame in the GetControlsGroupMainFrameStyle method, and set ControlsGroupMainFrameStyle = _Frame.Style;, but the _Frame.Style is null.

(Note: Because you get the device info in MainThread, and then set the style for Frame, it will cost a few seconds to load the page)

 public static Style GetControlsGroupMainFrameStyle()
      {
          MainThread.BeginInvokeOnMainThread(() =>
          {...
           
              //assign MyFrame style to the ControlsGroupMainFrame
           //   ControlsGroupMainFrameStyle = _Frame.Style;
              ControlsGroupMainFrameStyle = new Style(typeof(Frame))
              {
                 Setters =
                  {
                      new Setter
                      {
                          Property = Frame.BorderColorProperty,
                          Value = Color.FromArgb("#4c4c4c")
                      },
                       new Setter
                      {
                          Property = Frame.MarginProperty,
                          Value =  new Thickness(0, 0, 0, 5),
                      },
                        new Setter
                      {
                          Property = Frame.BackgroundColorProperty,
                          Value = Colors.Green
                      },
                         new Setter
                      {
                          Property = Frame.BorderColorProperty,
                          Value = Color.FromArgb("#4c4c4c")
                      },
                          new Setter
                      {
                          Property =  Frame.PaddingProperty,
                          Value = 0
                      },
                           new Setter
                      {
                          Property = Frame.CornerRadiusProperty,
                          Value = 5
                      },
                             new Setter
                      {
                          Property = Frame.HasShadowProperty,
                          Value = true
                      },
                              new Setter
                      {
                          Property = Frame.HorizontalOptionsProperty,
                          Value =  _Frame.HorizontalOptions
                      },
                              new Setter
                      {
                          Property = Frame.WidthRequestProperty,
                          Value =  _Frame.WidthRequest
                      },
                              new Setter
                      {
                          Property = Frame.MinimumWidthRequestProperty,
                          Value =  _Frame.MinimumWidthRequest
                      }
 
                  }
              };
          });
          //return style
          return ControlsGroupMainFrameStyle;
      }
  }

And then you can set the style : ControlsGroupMainFrame4.Style = MyStyles.GetControlsGroupMainFrameStyle();

Also, it's not clear how you set the Static Style in XAML. You can see Style apps using XAML - .NET MAUI | Microsoft Learn

Best Regards,

Wenyan Zhang

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