With Xamarin, I have a small UI element which acts as a content divider:
<BoxView StyleClass="contentDivider"
HeightRequest="2"
WidthRequest="1000"
Margin="3, 0"/>
Since I use this a number of times I wanted to be able to have the code written down once, and reuse that code - just like a class with its instance (DRY). It's most likely me being a blind bat and not being able to find how it's done. So, how can I reuse XAML elements?
You can do this with ContentViews (https://learn.microsoft.com/en-us/xamarin/xamarin-forms/user-interface/controls/layouts#contentview), which probably works better for larger reuse cases (using more XAML in the ContentView).
Yet, for such a small single element example as yours, you could really just consider using a global style (https://learn.microsoft.com/en-us/xamarin/xamarin-forms/user-interface/styles/xaml/application) which its looks like you already have with StyleClass="contentDivider", as long as you only want to override properties on a single element (like your BoxView).
Just add HeightRequest, WidthRequest and Margin to your style and your done.
<Style x:Key="contentDivider" TargetType="BoxView">
<Setter Property="HeightRequest" Value="20" />
<Setter Property="WidthRequest" Value="20" />
<Setter Property="Margin" Value="0,99,0,0" />
... etc
</Style>
Related
I am trying to learn how to use Styles most effectively in WinUI 3 (from WindowsAppSDK 1.1.1) but I'm having difficulty getting simple inheritance to work.
Consider the NavigationViewItem class. I'd like to modify the default style to bind the FontSize and Height properties. The following works in my Page XAML:
<NavigationViewItem x:Uid="Shell_05" helpers:NavigationHelper.NavigateTo="ViewModels._05CreditViewModel"
FontSize="{Binding ViewModel.RootShellFontSize, ElementName=shellPage}"
Height="{Binding ViewModel.CurrentMenuItemHeight, ElementName=shellPage}">
<NavigationViewItem.Icon>
<BitmapIcon UriSource="\Images\credit.png"/>
</NavigationViewItem.Icon>
</NavigationViewItem>
But adding the two properties to a page resource does not (although the FontSize property works in each of the following. It's the Height that doesn't):
<Page.Resources>
<Style TargetType="NavigationViewItem" >
<Setter Property="FontSize" Value="{Binding ViewModel.RootShellFontSize, ElementName=shellPage}" />
<Setter Property="Height" Value="{Binding ViewModel.CurrentMenuItemHeight, ElementName=shellPage}" />
</Style>
</Page.Resources>
Neither does adding the style to a resource dictionary and merging. I've read over what I can find about inheriting styles and the BasedOn="" extension is an explicit way to derive from an existing style in WinUI versions prior to 2.6 (I think). Apparently, WinUI 3 does not require BasedOn. In any case, simply specifying TargetType="NavigationViewItem" doesn't work, but nor does
<Style TargetType="controls:NavigationViewItem" BasedOn="DefaultNavigationViewItemStyle">
The source code for v1.1.1 of the SDK declares a default style for the NavigationViewItem in generic.xaml, but there is no definition for DefaultNavigationViewItemStyle.
I also cannot derive from the default style using
<Style TargetType="controls:NavigationViewItem" BasedOn="{StaticResource {x:Type NavigationViewItem}}">
because x:Type is undefined.
I can do all of the bindings I want in code but I assume it's both clearer and more efficient to do it in XAML.
How do I inherit, derive from, or override a portion of the default style for a WinUI 3 control (not a custom control) in a desktop application, please?
Thanks for any help. Pointers to good XAML for WinUI 3 documentation (or books and articles) would also be greatly appreciated.
In your case the height is most probably not working since page.resources get compiled before object initialization and the height of the CurrentMenuItemHeight is 0. To solve it just set the mode to one way as such
{Binding ViewModel.CurrentMenuItemHeight,Mode=OneWay , ElementName=shellPage}
When you wish to use BasedOn, just say BasedOn={ThemeResource styleName}.
Just make sure the style is actually defined in Generic.xaml file which u can find in "C:\Users\AdminName.nuget\packages\microsoft.windowsappsdk\1.1.1\lib\uap10.0\Microsoft.UI\Themes"
So your final page.resources should be as such:
<Page.Resources>
<Style TargetType="NavigationViewItem" >
<Setter Property="FontSize" Value="{Binding ViewModel.RootShellFontSize, ElementName=shellPage}" />
<Setter Property="Height" Value="{Binding ViewModel.CurrentMenuItemHeight, Mode=OneWay, ElementName=shellPage}" />
</Style>
</Page.Resources>
But it would be much better to use x:Bind instead of Binding. You can view this page to learn more about it https://learn.microsoft.com/en-US/windows/uwp/data-binding/data-binding-in-depth
As an Android developer I'm used to work with #dimen/-constants in Androids XML. I find this future useful because it allows me to easily change multiple places that should have the same pixel-length together.
Does Xamarin.Forms have a similar features that I can use?
Well what you looking for are ResourceDictionaries
XAML resources are definitions of objects that can be shared and re-used throughout a Xamarin.Forms application.
These resource objects are stored in a resource dictionary.
A ResourceDictionary is a repository for resources that are used by a Xamarin.Forms application. Typical resources that are stored in a ResourceDictionary include styles, control templates, data templates, colours, and converters.
In XAML, resources that are stored in a ResourceDictionary can then be retrieved and applied to elements by using the StaticResource markup extension. In C#, resources can also be defined in a ResourceDictionary and then retrieved and applied to elements by using a string-based indexer. However, there's little advantage to using a ResourceDictionary in C#, as shared objects can simply be stored as fields or properties, and accessed directly without having to first retrieve them from a dictionary.
Creating and Consuming a ResourceDictionary
Resources are defined in a ResourceDictionary that is then set to one of the following Resources properties:
The Resources property of any class that derives from Application.
The Resources property of any class that derives from VisualElement
A Xamarin.Forms program contains only one class that derives from Application but often makes use of many classes that derive from VisualElement, including pages, layouts, and controls. Any of these objects can have its Resources property set to a ResourceDictionary. Choosing where to put a particular ResourceDictionary impact where the resources can be used:
Resources in a ResourceDictionary that is attached to a view such as Button or Label can only be applied to that particular object, so this is not very useful.
Resources in a ResourceDictionary attached to a layout such as StackLayout or Grid can be applied to the layout and all the children of that layout.
Resources in a ResourceDictionary defined at the page level can be applied to the page and to all its children.
Resources in a ResourceDictionary defined at the application level can be applied throughout the application.
The following XAML shows resources defined in an application level ResourceDictionary in the App.xaml file created as part of the standard Xamarin.Forms program:
<Application ...>
<Application.Resources>
<ResourceDictionary>
<Color x:Key="PageBackgroundColor">Yellow</Color>
<Color x:Key="HeadingTextColor">Black</Color>
<Color x:Key="NormalTextColor">Blue</Color>
<Style x:Key="LabelPageHeadingStyle" TargetType="Label">
<Setter Property="FontAttributes" Value="Bold" />
<Setter Property="HorizontalOptions" Value="Center" />
<Setter Property="TextColor" Value="{StaticResource HeadingTextColor}" />
</Style>
</ResourceDictionary>
</Application.Resources>
Beginning in Xamarin.Forms 3.0, the explicit ResourceDictionary tags are not required. The ResourceDictionary object is created automatically, and you can insert the resources directly between the Resources property-element tags:
<Application ...>
<Application.Resources>
<Color x:Key="PageBackgroundColor">Yellow</Color>
<Color x:Key="HeadingTextColor">Black</Color>
<Color x:Key="NormalTextColor">Blue</Color>
<Style x:Key="LabelPageHeadingStyle" TargetType="Label">
<Setter Property="FontAttributes" Value="Bold" />
<Setter Property="HorizontalOptions" Value="Center" />
<Setter Property="TextColor" Value="{StaticResource HeadingTextColor}" />
</Style>
</Application.Resources>
Each resource has a key that is specified using the x:Key attribute, which becomes it dictionary key in the ResourceDictionary. The key is used to retrieve a resource from the ResourceDictionary by the StaticResource markup extension, as demonstrated in the following XAML code example that shows additional resources defined within the StackLayout:
<StackLayout Margin="0,20,0,0">
<StackLayout.Resources>
<ResourceDictionary>
<Style x:Key="LabelNormalStyle" TargetType="Label">
<Setter Property="TextColor" Value="{StaticResource NormalTextColor}" />
</Style>
<Style x:Key="MediumBoldText" TargetType="Button">
<Setter Property="FontSize" Value="Medium" />
<Setter Property="FontAttributes" Value="Bold" />
</Style>
</ResourceDictionary>
</StackLayout.Resources>
<Label Text="ResourceDictionary Demo" Style="{StaticResource LabelPageHeadingStyle}" />
<Label Text="This app demonstrates consuming resources that have been defined in resource dictionaries."
Margin="10,20,10,0"
Style="{StaticResource LabelNormalStyle}" />
<Button Text="Navigate"
Clicked="OnNavigateButtonClicked"
TextColor="{StaticResource NormalTextColor}"
Margin="0,20,0,0"
HorizontalOptions="Center"
Style="{StaticResource MediumBoldText}" />
</StackLayout>
For more detailed information kindly take a look here
Apart from the StaticResource as mentioned above, 2 other ways to do it.
First one is, Having static class for constants and refer them in the XAML.
public static class GlobalSetting
{
public static double ImageRotation { get { return 180; } }
}
In the Xaml, you need to add this namespace in the page directive,
xmlns:gb="clr-namespace:XXXX.StaticData"
and use the constant in the xaml code as below,
<Image Source="icon_back.png" Rotation="{x:Static gb:GlobalSetting.BackImageRotation}" HeightRequest="24" </Image>
Second approach is, having a constant parameter in the BaseViewModel, and binding them in the Xaml code.
Sounds to me like you want to define constants/styles in a ResourceDictionary:
https://learn.microsoft.com/en-us/xamarin/xamarin-forms/xaml/resource-dictionaries.
In the ResourceDictionary you can define your constants/styles by key, in your XAML you can then refer to them as follows:
Color={StaticResource MyColorFromDictionary}
I'm making a ResourceDictionary of common styles that are used throughout my application and one of them is:
<Style x:Key="ME_BASE_AppbarButtonSaveStyle"
TargetType="AppBarButton">
<Setter Property="Label"
Value="Save" />
<Setter Property="ToolTipService.ToolTip"
Value="Save" />
<Setter Property="Icon">
<Setter.Value>
<FontIcon FontFamily="Segoe MDL2 Assets"
Glyph="" />
</Setter.Value>
</Setter>
</Style>
It's all ok if I apply the style only one AppbarButton on the Page, but if I want to have two buttons with the same style, I get the following error:
The parameter is incorrect
It's of ok (no error) if I remove the icon property out of the style...
But that's kind of missing the point...
Anyone experienced something similar? Perhaps...
Thank you for all the help.
Error HRESULT E_Fail has been returned from a call to a COM component.
This error will occurred when you use this style for the second AppBarButton. This error usually happens when a reference to a style or an event handler that does not exist or is not with the context of the XAML, you can see the exception information of your problem:
If you read this document: XAML resources must be shareable, you will find:
Custom types used as resources can't have the UIElement class in their inheritance, because a UIElement can never be shareable (it's always intended to represent exactly one UI element that exists at one position in the object graph of your runtime app).
Whether a Icon property of AppBarButton or a FontIcon derives from UIElement, so I guess this is the reason why can't this property be styled in the resource dictionary.
Besides, I will consider if this is a right direction to define the Icon property for each AppBarButton in the style, normally I'd like give each button a different icon as content.
But if you insist to do this, I can provide you a workaround method by defining the Content of the AppBarButton, this is the construction of your AppBarButton:
You use a FontIcon as the content of the AppBarButton, so we can modify your style like this:
<Style x:Key="ME_BASE_AppbarButtonSaveStyle" TargetType="AppBarButton">
<Setter Property="Label" Value="Save" />
<Setter Property="ToolTipService.ToolTip" Value="Save" />
<Setter Property="ContentTemplate">
<Setter.Value>
<DataTemplate>
<FontIcon FontFamily="Segoe MDL2 Assets"
Glyph="" />
</DataTemplate>
</Setter.Value>
</Setter>
</Style>
What is the correct way to apply styles on elements with a condition on their parent element's type, i. e. only if they are children of certain other elements?
In my case, I want to apply some exact button width and height, but only if those buttons are direct children of a stackpanel. Additionally, a second style should be applied to images within those buttons (glyphs).
How do I define a button style that only affects buttons on a stackpanel, but not those buttons placed directly on a grid?
Is it possible to add additional conditions such as only stackpanels with orientation="horizontal"?
Can I define "tree conditions" like only images on buttons on [horizontal] stackpanels?
As 90% of all buttons in my application are those on the stackpanels, so far I've applied the style to all buttons and images and overrode it where necessary. But this isn't the best solution, is it?
Preferably, the solution would deal with all the conditions in the style definition, so I won't have to explicitly assign that style to every single one of my stackpanels.
<StackPanel>
<StackPanel.Resources>
<Style x:Key="Rectangle1" TargetType="Rectangle">
<Setter Property="Stroke" Value="Black" />
<Setter Property="Fill" Value="White" />
</Style>
</StackPanel.Resources>
<UniformGrid Columns="10">
<UniformGrid.Resources>
<Style TargetType="Rectangle" BasedOn="{StaticResource Rectangle1}">
<Setter Property="Fill" Value="Red" />
</Style>
</UniformGrid.Resources>
</UniformGrid>
</StackPanel>
I have entity with property IsRemoved. When it is become true grid row should be Gray.
To do this I am using this code:
<dxg:TableView.RowStyle>
<Style TargetType="{x:Type dxg:GridRowContent}">
<Style.Triggers>
<DataTrigger Binding="{Binding DataContext.IsRemoved, Mode=OneWay}" Value="True">
<Setter Property="Background" Value="Gray" />
</DataTrigger>
</Style.Triggers>
</Style>
</dxg:TableView.RowStyle>
</dxg:TableView>
But It will run only when grid shows first time. I want to change color when value is changing. Property implement INotifyPropertyChange Event.
Note: this answer is legacy (see my other answer).
This answer is for DevExpress versions prior to v14.1, or DevExpress versions v14.1 and after with
UseLightweightTemplates="None".
You need to have an initial setter for the property you want to change. This is due to the order in which WPF uses styles.
Include this line after your style tag:
<Setter Property="Background" Value="Black" />
Full Example:
<dxg:TableView.RowStyle>
<Style TargetType="{x:Type dxg:GridRowContent}">
<Setter Property="Background" Value="Black" />
<Style.Triggers>
<DataTrigger Binding="{Binding DataContext.IsRemoved, Mode=OneWay}" Value="True">
<Setter Property="Background" Value="Gray" />
</DataTrigger>
</Style.Triggers>
</Style>
</dxg:TableView.RowStyle>
Starting with v14.1 of DevExpress, they introduced Optimized Mode which uses Lightweight Templates. This makes everything faster, but requires a change to how the styles and DataTriggers are specified.
Lightweight Templates are controlled by a the attached property UseLightweightTemplates="Row", which is on by default. It can be switched to None for backwards compatibility.
Here is a working MVVM example of how to color a row if the IsDirty property is set for any grid row.
<dxg:GridControl x:Name="MyGridControl"
ItemsSource ="{Binding MyViewModelList}"
SelectionMode="None"
VerticalAlignment="Stretch">
<dxg:GridControl.Resources>
<SolidColorBrush x:Key="GridRowIsDirty" Color="#FF602D2D" />
</dxg:GridControl.Resources>
<dxg:GridControl.View>
<dxg:TableView UseLightweightTemplates="Row" >
<dxg:TableView.RowStyle>
<Style TargetType="dxg:RowControl">
<Style.Triggers>
<DataTrigger Binding="{Binding Row.IsDirty}" Value="True">
<Setter Property="Background" Value="{StaticResource GridRowIsDirty}" />
</DataTrigger>
</Style.Triggers>
</Style>
</dxg:TableView.RowStyle>
</dxg:TableView>
</dxg:GridControl.View>
<dxg:GridControl.Columns>
<dxg:GridColumn x:Name="Included" FieldName="Included"/>
<dxg:GridColumn x:Name="ColumnB" Header="Column B" FieldName="ColumnB" ReadOnly="True"/>
<dxg:GridColumn x:Name="ColumnC" Header="Column C" FieldName="ColumnC" ReadOnly="True"/>ReadOnly="True"/>
</dxg:GridControl.Columns>
</dxg:GridControl>
In the ViewModel behind this grid:
public ObservableCollection<MyViewModel> MyViewModelList { get; set; }
Every row in the grid points to a class of type MyViewModel, which contains a custom IsDirty flag which we can set on demand:
public bool IsDirty
{
get { return _isDirty; }
set
{
_isDirty = value;
OnPropertyChanged();
}
}
Appendix A: Additional Links
See DevExpress: How to disable focused/selected row colors.
See DevExpress: Optimized Mode.
See DevExpress: DXGrid: DataTrigger does not seem to work with UseLightweightTemplates="All".
See DevExpress: Binding to the RowData.Row property is not updated when changing a specific data row property.
See DevExpress: DxGrid: Grid does not update until I scroll the row on off and one the screen.
Appendix B: Other solutions
This also works most of the time, but it will not work if the source of the event is via a context menu, so it is not recommended:
<DataTrigger Binding="{Binding DataContext.IsDirty}" Value="True">
<Setter Property="Background" Value="{StaticResource GridRowIsDirty}" />
</DataTrigger>
Appendix C: AllowLiveDataShaping
If the trigger is not firing, try switching on AllowLiveDataShaping="True" in <GridControl>. However, try to avoid this as it (theoretically) has an impact on the speed of large, complex grids (it has no discernable impact on most grids of a reasonable size).
Appendix D: If all else fails, use a custom ControlTemplate
With the introduction of "UseLightweightTemplates", DevExpress has been focusing on speed. However, the techniques used for speed involve switching off bindings that might slow things down.
This means that if we change something in a DxGrid cell, the value in the ViewModel does not change until the user shifts to the next cell or row. This means that the ViewModel lags behind what is actually in the grid.
To fix this, the only solution that I could find was to bypass DevExpress's templates entirely, and use my own. This means that the DxGrid has no choice but to display a custom template which updates the ViewModel instantaneously as soon as the user edits it, which means that the row color changes immediately:
<dxg:GridControl Grid.Row="3" x:Name="TrsGridControl"
ItemsSource ="{Binding MyObservableCollection}"
VerticalAlignment="Stretch"
AllowLiveDataShaping ="True">
<dxg:GridControl.Resources>
<converter:TestConverter x:Key="TestConverter" />
<ControlTemplate x:Key="DisplayedOnTicketTrs">
<dxe:CheckEdit x:Name="DisplayedOnTicketCheckEdit" HorizontalAlignment="Center" IsChecked="{Binding RowData.Row.DisplayedOnTicket, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
</ControlTemplate>
</dxg:GridControl.Resources>
<dxg:GridControl.View>
<dxg:TableView UseLightweightTemplates="All"/>
</dxg:GridControl.View>
<dxg:GridControl.Columns>
<dxg:GridColumn x:Name="DisplayedOnTicketTrs" DisplayTemplate="{StaticResource DisplayedOnTicketTrs}" Header="Displayed On Ticket?" HeaderToolTip="Displayed On Ticket?" AllowEditing="False"/>
Header ="Displayed On Ticket?"/>
<dxg:GridColumn x:Name="ColumnA" Header="ColumnA" FieldName="ColumnA" ReadOnly="True"/>
<dxg:GridColumn x:Name="ColumnB" Header="ColumnB" FieldName="ColumnB" ReadOnly="True"/>
</dxg:GridControl.Columns>
</dxg:GridControl>
After I made this change, everything started to work:
When the checkbox is clicked, the background color changes instantly (if we add the trigger to change the background color, above).
Editing the DxGrid changes the ViewModel instantaneously.
Changing the ViewModel updates the DxGrid instantaneously.
If a ContextMenu updates the ViewModel, then everything just works.
you should write just "Row" instead of "DataContext"