VisualState Setter中的UWP绑定

Question

实际上是否可以在VisualState中使用带有Setters Value属性的绑定,因为当我尝试使用x时:绑定页面的初始视图不使用绑定和绑定页面不会使用它们或者我是否需要做些额外的事情？

例如,如果我使用下面的布局并且我启动宽度在400-800之间的应用程序,则PassInput Passwordbox将没有占位符.当我将窗口大小调整为800以上然后返回时,它将最终具有占位符.

例:

<Page
    x:Class="UWP.Learning.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d"
    x:Name="Page">
    <RelativePanel Background="White">
        <VisualStateManager.VisualStateGroups>
            <VisualStateGroup x:Name="WindowSizeStates">
                <VisualState x:Name="SmallState">
                    <VisualState.StateTriggers>
                        <AdaptiveTrigger MinWindowWidth="400" />
                    </VisualState.StateTriggers>
                    <VisualState.Setters>
                        <Setter Target="PassInput.PlaceholderText" Value="{x:Bind MyPlaceHolder, Mode=OneWay}" />
                    </VisualState.Setters>
                </VisualState>
                <VisualState x:Name="WideState">
                    <VisualState.StateTriggers>
                        <AdaptiveTrigger MinWindowWidth="800" />
                    </VisualState.StateTriggers>
                    <VisualState.Setters>
                        <Setter Target="PassInput.PlaceholderText" Value="{x:Null}" />
                    </VisualState.Setters>
                </VisualState>
            </VisualStateGroup>
        </VisualStateManager.VisualStateGroups>
        <TextBlock
            Name="PassLabel"
             RelativePanel.AlignTopWithPanel="True"
             RelativePanel.AlignLeftWithPanel="True"
             RelativePanel.AlignRightWithPanel="True"
             Text="Pass input label"
             HorizontalAlignment="Center" />
        <PasswordBox
             Name="PassInput"
             RelativePanel.AlignLeftWithPanel="True"
             RelativePanel.AlignRightWithPanel="True"
             RelativePanel.Below="PassLabel"
             VerticalAlignment="Center"
             Margin="20,0" />
    </RelativePanel>
</Page>

代码背后:

namespace UWP.Learning
{
    using Windows.UI.Xaml.Controls;

    public sealed partial class MainPage : Page
    {
        public MainPage() { this.InitializeComponent(); }
        public string MyPlaceHolder => "FOOBAR";
    }
}

Answer 1

对我来说看起来像个错误.一个简单的解决方法是在Loaded活动中进行一次性检查.

Loaded += (s, e) =>
{
    switch (ActualWidth)
    {
        case var w when (w >= 400 && w < 800):
            VisualStateManager.GoToState(this, "SmallState", false);
            break;
        case var w when (w >= 800):
            VisualStateManager.GoToState(this, "WideState", false);
            break;
    }
};