将 UWP VisualStateManager 与变量一起使用

Question

I can use VisualStateManager to change individual properties of controls. Something like this:

           <VisualStateManager.VisualStateGroups>
            <VisualStateGroup>
                <VisualState>
                    <VisualState.StateTriggers>
                        <!--small window-->
                        <AdaptiveTrigger MinWindowHeight="0" MinWindowWidth="0"/>
                    </VisualState.StateTriggers>
                    <VisualState.Setters>
                        <Setter Target="Control1.FontSize" Value="13"/>
                        <Setter Target="Control2.FontSize" Value="13"/>
                        <Setter Target="Control3.FontSize" Value="13"/>
                        <Setter Target="Control4.FontSize" Value="13"/>
                    </VisualState.Setters>
                </VisualState>
                <VisualState>
                    <VisualState.StateTriggers>
                        <!--large window-->
                        <AdaptiveTrigger MinWindowHeight="665" MinWindowWidth="1000"/>
                    </VisualState.StateTriggers>
                    <VisualState.Setters>
                        <Setter Target="Control1.FontSize" Value="24"/>
                        <Setter Target="Control2.FontSize" Value="24"/>
                        <Setter Target="Control3.FontSize" Value="24"/>
                        <Setter Target="Control4.FontSize" Value="24"/>
                    </VisualState.Setters>
                </VisualState>
            </VisualStateGroup>
        </VisualStateManager.VisualStateGroups>

This works but is soooo much typing!

Is it possible to use VisualStateManager to set a value for the font and than refer to this variable in XAML?

Something like this:

          <VisualStateManager.VisualStateGroups>
            <VisualStateGroup>
                <VisualState>
                    <VisualState.StateTriggers>
                        <!--small window-->
                        <AdaptiveTrigger MinWindowHeight="0" MinWindowWidth="0"/>
                    </VisualState.StateTriggers>
                    <VisualState.Setters>
                        <Setter Target="@MyFontSize" Value="13"/>
                    </VisualState.Setters>
                </VisualState>
                <VisualState>
                    <VisualState.StateTriggers>
                        <!--large window-->
                        <AdaptiveTrigger MinWindowHeight="665" MinWindowWidth="1000"/>
                    </VisualState.StateTriggers>
                    <VisualState.Setters>
                        <Setter Target="@MyFontSize" Value="24"/>
                    </VisualState.Setters>
                </VisualState>
            </VisualStateGroup>
        </VisualStateManager.VisualStateGroups>

I could then use @MyFontSize variable in XAML when designing controls and I could change it in one place.

<TextBlock x:Name="Control1" FontSize="@MyFontSize"/>
<TextBlock x:Name="Control2" FontSize="@MyFontSize"/>
<TextBlock x:Name="Control3" FontSize="@MyFontSize"/>

Is it possible to do something like this with UWP VisualStateManager ?

Answer 1

Is it possible to use VisualStateManager to set a value for the font and than refer to this variable in XAML

I'm afraid you can't set variable within VisualStateManager , But for your scenario, we have a workaround that use Setting class as medium and effect other TextControl with MVVM bind.

For example

public class Setting : INotifyPropertyChanged
{
    private double _fontSize = 10;
    public double CFontSize
    {
        get { return _fontSize; }
        set { _fontSize = value; OnPropertyChanged(); }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    protected void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

Usage

<Page.Resources>
    <local:Setting x:Key="Setting" />
</Page.Resources>
<StackPanel>
    <TextBlock
        x:Name="BaseControl"
        VerticalAlignment="Center"
        FontSize="{Binding CFontSize, Source={StaticResource Setting}, Mode=TwoWay}"
        Text="Hello" />
    <TextBlock
        x:Name="Control1"
        VerticalAlignment="Center"
        FontSize="{Binding CFontSize, Source={StaticResource Setting}, Mode=TwoWay}"
        Text="How are you" />
    <TextBlock
        x:Name="Control2"
        VerticalAlignment="Center"
        FontSize="{Binding CFontSize, Source={StaticResource Setting}, Mode=TwoWay}"
        Text="Fine thank you, and you?" />

    <VisualStateManager.VisualStateGroups>
        <VisualStateGroup>
            <VisualState>
                <VisualState.StateTriggers>
                    <!--  small window  -->
                    <AdaptiveTrigger MinWindowHeight="0" MinWindowWidth="0" />
                </VisualState.StateTriggers>
                <VisualState.Setters>
                    <Setter Target="BaseControl.FontSize" Value="13" />
                </VisualState.Setters>
            </VisualState>
            <VisualState>
                <VisualState.StateTriggers>
                    <!--  large window  -->
                    <AdaptiveTrigger MinWindowHeight="665" MinWindowWidth="1000" />
                </VisualState.StateTriggers>
                <VisualState.Setters>
                    <Setter Target="BaseControl.FontSize" Value="24" />
                </VisualState.Setters>
            </VisualState>
        </VisualStateGroup>
    </VisualStateManager.VisualStateGroups>
</StackPanel>

Answer 2

Found a similar but simpler way to do this inspired by @Nico Zhu's approach. Sharing here in case someone else finds it useful.

My approach is to use one control as a template and bind all other controls of that type to it.

The VisualStateManager sets the property for the "master" controls:

  <VisualStateManager.VisualStateGroups>
            <VisualStateGroup>

                <VisualState>
                    <VisualState.StateTriggers>
                        <!--VisualState to be triggered when window width is <665 effective pixels.-->

                        <AdaptiveTrigger MinWindowHeight="0" MinWindowWidth="0"/>
                    </VisualState.StateTriggers>
                    <VisualState.Setters>
                        <Setter Target="txtHeader.FontSize" Value="13"/>
                        <Setter Target="txtRegular.FontSize" Value="10"/>
                    </VisualState.Setters>
                </VisualState>
                <VisualState>
                    <VisualState.StateTriggers>
                        <AdaptiveTrigger MinWindowHeight="665" MinWindowWidth="1000"/>
                    </VisualState.StateTriggers>
                    <VisualState.Setters>
                        <Setter Target="txtHeader.FontSize" Value="20"/>
                        <Setter Target="txtRegular.FontSize" Value="16"/>
                    </VisualState.Setters>
                </VisualState>
            </VisualStateGroup>
        </VisualStateManager.VisualStateGroups>

All other controls can bind to "master" controls.

<TextBlock Text="My Header 1" FontSize="{Binding ElementName=txtHeader, Path=FontSize}" />
<TextBlock Text="My Header 2" FontSize="{Binding ElementName=txtHeader, Path=FontSize}" />
<TextBlock Text="My regular text 1" FontSize="{Binding ElementName=txtRegular, Path=FontSize}" />
<TextBlock Text="My regular text 2" FontSize="{Binding ElementName=txtRegular, Path=FontSize}" />

When a user resizes page, VisualStateManager will change the master controls, all others will get it through binding.

If you want to, you can create hidden controls just to server as templates.