c# - XAML 中的固定定位

Question

我有一个 Windows 应用商店风格的 WPF 应用程序，我刚刚向其中添加了搜索功能。当我单击应用栏中的“搜索”按钮时，我将包含 SearchBox 的 FlyoutPresenter 设置为 Visible。这个按钮位于右下角。它在带键盘的计算机上运行良好，但当虚拟键盘或 InputPane 打开时我遇到了问题。首先，键盘覆盖了盒子。当框处于焦点时，我通过检查和调整框的边距解决了这个问题，但是当我将页面滚动到最顶部和最底部时，控件开始在页面上移动。这是我的最小代码:

XAML:

<Grid Background="White" x:Name="MainGrid">

    <!-- App Bar with Search button -->
    <AppBar x:Name="BAppBar" VerticalAlignment="Bottom">
        <CommandBar>
            <CommandBar.PrimaryCommands>
                <AppBarButton Icon="Find" Label="Search" Click="Search_Click"/>
            </CommandBar.PrimaryCommands>
        </CommandBar>
    </AppBar>

    <!-- Search button and Close button -->
    <FlyoutPresenter VerticalAlignment="Top" Name="SearchPop" Visibility="Collapsed">
        <StackPanel Orientation="Horizontal">
            <SearchBox Name="Search" GotFocus="Search_Focus" LostFocus="Search_Focus"/>
            <AppBarButton Name="SearchClose" Icon="Cancel" Click="Search_Close" />
        </StackPanel>
    </FlyoutPresenter>
</Grid>

C#:

public partial class MainPage : Page
{
    public MainPage()
    {
        this.InitializeComponent();
    }

    // Close app bar, show search box, and set margin to bottom of page
    private void Search_Click(object sender, RoutedEventArgs e)
    {
        BAppBar.IsOpen = false;
        SearchPop.Visibility = Windows.UI.Xaml.Visibility.Visible;

        SearchPop.Margin = new Thickness(0, MainGrid.ActualHeight - SearchPop.ActualHeight, 0, 0);
    }

    // Set margin for opening/closing virtual keyboard
    private void Search_Focus(object sender, RoutedEventArgs e)
    {
        Windows.UI.ViewManagement.InputPane.GetForCurrentView().Showing += (s, args) =>
        {
            double flyoutOffset = (int)args.OccludedRect.Height - SearchPop.ActualHeight;
            SearchPop.Margin = new Thickness(0, flyoutOffset, 0, 0);
        };
        Windows.UI.ViewManagement.InputPane.GetForCurrentView().Hiding += (s, args) =>
        {
            SearchPop.Margin = new Thickness(0, MainGrid.ActualHeight - SearchPop.ActualHeight, 0, 0);
        };
    }

    // Close search
    private void Search_Close(object sender, RoutedEventArgs e)
    {
        SearchPop.Visibility = Windows.UI.Xaml.Visibility.Collapsed;
    }
}

我需要的是框不受用户在屏幕中滚动的影响。在 HTML 中，这称为固定定位。我已经读到它在 XAML 中本身是不可能的，但是有一些解决方法。我已阅读这些 MSDN 和 SO 链接，但它们并没有真正帮助:

http://social.msdn.microsoft.com/Forums/en-US/9779328a-a7cd-447d-a4ac-bcc952083f43/fixed-positioning-in-wpf?forum=wpf

http://social.msdn.microsoft.com/Forums/windowsapps/en-US/7349d01d-dc0e-4e1c-9327-df90e00fbebf/how-to-handle-the-appearance-of-the-onscreen-keyboard?forum=winappswithcsharp

Popup control moves with parent

Answer 1

您可以通过一种非常简单的方式在 XAML 中模拟固定行为:

<Grid Background="White" x:Name="MainGrid">
    <ContentControl VerticalAligment="Stretch" HorizontalAligment="Stretch">
    <!--All other visual controls, the float item will be located over all controls    located here, even scrolls viewers-->
    </ContentControl>

    <!-- Float item -->
    <SomeControl>
    <!--The control you want be over in the fixed position, 
        you can set the layout to it, and locate it where you want
        just set the Vertical/Horizontal Aligment, margin, height, width-->
    </SomeControl>
</Grid>

(很抱歉，如果代码示例有一些语法错误，我是即时编写的)wpf 也有一些控件显示在所有其他控件之上，这些元素是上下文菜单、工具提示和装饰器，您也可以尝试它们。

希望这些想法对您有所帮助。