UWP Development, Extension of Style

Introduction
UWP (Universal Windows Platform) development is a development platform that allows the same app to run on various Windows devices. One of the powerful features of UWP is the use of Styles. Styles define the visual properties of user interface (UI) elements, enhancing the consistency of applications and making maintenance easier. In this post, we will explain in detail how to extend styles in UWP and provide practical examples to aid understanding.

1. Basics of UWP Styles

Styles are declared using a ResourceDictionary defined in XAML. These styles define various properties of UI elements, making them reusable and helping to maintain the consistency of the UI. By default, styles consist of the following components:

  • TargetType: The type of UI element to which the style will be applied (e.g., Button, TextBox, etc.)
  • Setters: A set of Setter that set the values of properties defined in the style

1.1 Basic Style Example

<Page.Resources>
    <Style TargetType="Button">
        <Setter Property="Background" Value="SkyBlue"/>
        <Setter Property="Foreground" Value="White"/>
        <Setter Property="FontSize" Value="16"/>
        <Setter Property="Padding" Value="10,5"/>
    </Style>
</Page.Resources>

This example defines a basic style for a Button on a UWP page. By setting the background color, foreground color, font size, and padding of the button, it ensures that all buttons appear in a consistent manner.

2. Extending Styles

In addition to basic definitions, styles can be extended to suit specific situations. This allows the same UI element to have different visual representations depending on the context. There are various methods to extend styles, and here we will explain using Derived Styles.

2.1 Inheriting Styles

Style inheritance allows one style to be set as the base style, and other styles can be extended based on this. This can be implemented using the `BasedOn` property.

<Page.Resources>
    <Style x:Key="BaseButtonStyle" TargetType="Button">
        <Setter Property="Background" Value="SkyBlue"/>
        <Setter Property="Foreground" Value="White"/>
    </Style>

    <Style TargetType="Button" BasedOn="{StaticResource BaseButtonStyle}">
        <Setter Property="FontSize" Value="20"/>
        <Setter Property="Padding" Value="15,10"/>
    </Style>
</Page.Resources>

The second style created here can still use the properties of `BaseButtonStyle` while adding additional settings. This reduces code redundancy and simplifies maintenance.

2.2 State-Based Styles

State-based styles are a powerful tool for changing the appearance of UI elements based on user interactions. For example, they can provide visual feedback when a button is hovered over or clicked.

<Style TargetType="Button">
        <Setter Property="Background" Value="SkyBlue"/>
        <Setter Property="Foreground" Value="White"/>
        <Setter Property="FontSize" Value="16"/>

        <Style.Triggers>
            <Trigger Property="IsMouseOver" Value="True">
                <Setter Property="Background" Value="DodgerBlue"/>
            </Trigger>

            <Trigger Property="IsPressed" Value="True">
                <Setter Property="Background" Value="DarkBlue"/>
            </Trigger>
        </Style.Triggers>
    </Style>

This example defines a style that changes the background color of a button when hovered over or clicked. This provides immediate feedback to the user.

3. Customized Control Styles

We often want to change the styles of built-in controls to create a unique UI. In such cases, ControlTemplate can be used to redefine the entire structure of a control.

3.1 Defining a ControlTemplate

Here is an example of customizing a Button using its ControlTemplate:

<Button Content="Click Me">
        <Button.Template>
            <ControlTemplate TargetType="Button">
                <Grid Background="{TemplateBinding Background}">
                    <ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center"/>
                </Grid>
            </ControlTemplate>
        </Button.Template>
    </Button>

In the above example, we replaced the default structure of the Button with a `Grid` and used a ContentPresenter to center the button’s content. The use of TemplateBinding allows us to change the structure completely while retaining the button’s background color.

3.2 Applying Additional Styles

Once a ControlTemplate is defined, it can be used alongside styles. You can still set properties through the style:

<Page.Resources>
        <Style TargetType="Button">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="Button">
                        <Grid Background="{TemplateBinding Background}">
                            <ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center"/>
                        </Grid>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
            <Setter Property="Background" Value="SkyBlue"/>
            <Setter Property="Foreground" Value="White"/>
        </Style>
    </Page.Resources>

This style ensures that all buttons receive the specified background and foreground colors along with the customized ControlTemplate. This allows for easy user customization while maintaining UI consistency.

4. Advanced Styling Techniques

In UWP, various techniques allow for the creation of more sophisticated and polished UIs using styles. Here, we will cover data-based styles and triggered styles.

4.1 Data-Based Styles

DataBinding allows the style of UI elements to be represented differently based on data. This provides customized responses to users and flexibility for developers in maintenance.

<Page.Resources>
        <Style TargetType="Button">
            <Setter Property="Background" Value="{Binding ButtonColor}"/>
            <Setter Property="Foreground" Value="White"/>
        </Style>
    </Page.Resources>

Here, we use data binding to ensure that the button’s background color is determined by a property called ButtonColor. This approach is useful for creating a more dynamic UI.

4.2 Using Provided Triggers

Another advanced technique involves state transitions through the VisualStateManager. The VisualStateManager is a useful tool for switching visual representations based on a control’s state.

<VisualStateManager.VisualStateGroups>
        <VisualStateGroup x:Name="CommonStates">
            <VisualState x:Name="Normal"/>
            <VisualState x:Name="PointerOver">
                <Storyboard>
                    <ColorAnimation Storyboard.TargetName="MyButton" Storyboard.TargetProperty="(Button.Background).(SolidColorBrush.Color)" To="Yellow" Duration="0:0:0.2"/>
                </Storyboard>
            </VisualState>
        </VisualStateGroup>
    </VisualStateManager.VisualStateGroups>

The above code shows an example of changing the background color of a button based on its state. When entering the PointerOver state, the background color changes to yellow. This provides an intuitive interface for users.

5. Conclusion

The extension of styles in UWP is a powerful feature that helps developers create dynamic and responsive UIs for their applications. By combining various styling techniques, it is possible to provide a better user experience. This post covered the basic principles of styles, state-based styles, ControlTemplate, and data binding. We hope you leverage these techniques to develop unique and user-friendly apps.

Finally, learning all possible styles and properties in UWP styling can take time, but these techniques will significantly streamline your development process.

We hope that continuous learning about UWP development will be very beneficial to you. If you have any additional questions, feel free to reach out through ChatGPT!