c# - FocusedElement 没有得到尊重

Question

我使用 Prism 和 MVVM 创建了一个基本应用程序。到目前为止，它仅由 Shell 和一个 View/ViewModel 组成。

在应用程序加载过程中，我将 View 加载到我的主要区域中并显示在屏幕上。这有效，但我无法让 View 上的文本框聚焦。 看起来光标在框中(虽然它没有闪烁)，但它不接受文本输入，直到我单击文本框。

我在一个新项目中重新创建了它，我所做的只是安装 prism/prism.unityextensions，设置 shell 和 View ，并将 View 加载到 shell 区域。这两个 xaml 文件的代码背后都没有任何内容。

外壳

<Window x:Class="MVVMFocusTest.Shell"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:prism="http://www.codeplex.com/prism"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <DockPanel LastChildFill="True">            
            <ContentControl Name="MainRegion" DockPanel.Dock="Top" prism:RegionManager.RegionName="MainRegion" />
        </DockPanel>
    </Grid>
</Window>

View 1

<UserControl x:Class="MVVMFocusTest.View1"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             mc:Ignorable="d" 
             d:DesignHeight="300" d:DesignWidth="300">
    <StackPanel>
        <Grid FocusManager.FocusedElement="{Binding ElementName=Username}">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="100" />
                <ColumnDefinition Width="*" />
            </Grid.ColumnDefinitions>
            <Grid.RowDefinitions>
                <RowDefinition />
                <RowDefinition Height="Auto" />               
            </Grid.RowDefinitions>

            <Label Grid.Row="0" Grid.Column="0">Username</Label>
            <TextBox Name="Username" Grid.Row="0" Grid.Column="1" ToolTip="Enter Username" TabIndex="0" />
            <Label Grid.Row="1" Grid.Column="0">Password</Label>
            <PasswordBox Grid.Row="1" Grid.Column="1" Name="LoginPassword" PasswordChar="*" ToolTip="Enter Password" TabIndex="1" />

        </Grid>
    </StackPanel>
</UserControl>

谁能指出我做错了什么？据我所知，FocusManager.FocusedElement="{Binding ElementName=Username}" 应该足以设置焦点。

Answer 1

根据 FocusManager文档 -

Logical focus pertains to the FocusManager.FocusedElement within a specific focus scope.

因此，它的 not necessary that element with logical focus will have keyboard focus as well但反之亦然，即 element with keyboard focus will surely have a logical focus as well.

如文档中所述 FocusManager.FocusedElement guarantees logical focus and not keyboard focus .所以你可以做的是创建一个 attach behaviour类似于 FocusManager.FocusedElement这将 set keyboard focus on an element .

您可以引用此使用附加行为设置键盘焦点 - Setting keyboard focus in WPF .

那篇文章的代码-

namespace Invoices.Client.Wpf.Behaviors
{
    using System.Windows;
    using System.Windows.Input;

    public static class KeyboardFocus
    {
        public static readonly DependencyProperty OnProperty;

        public static void SetOn(UIElement element, FrameworkElement value)
        {
            element.SetValue(OnProperty, value);
        }

        public static FrameworkElement GetOn(UIElement element)
        {
            return (FrameworkElement)element.GetValue(OnProperty);
        }

        static KeyboardFocus()
        {
            OnProperty = DependencyProperty.RegisterAttached("On", typeof(FrameworkElement), typeof(KeyboardFocus), new PropertyMetadata(OnSetCallback));
        }

        private static void OnSetCallback(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs dependencyPropertyChangedEventArgs)
        {
            var frameworkElement = (FrameworkElement)dependencyObject;
            var target = GetOn(frameworkElement);

            if (target == null)
                return;

            frameworkElement.Loaded += (s, e) => Keyboard.Focus(target);
        }
    }
}

在 XAML 中使用 -

<UserControl xmlns:behaviors="clr-namespace:Invoices.Client.Wpf.Behaviors">
    <Grid behaviors:KeyboardFocus.On="{Binding ElementName=TextBoxToFocus}">
        <TextBox x:Name="TextBoxToFocus" />
    </Grid>
</UserControl>