FocusedElement 未得到尊重

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。

在应用程序加载期间，我将视图加载到我的主区域中，并将其显示在屏幕上。这可行，但我无法使视图上的文本框聚焦。它looks就像光标在框中一样（尽管它没有闪烁），但在我单击文本框之前它不接受文本输入。

我在一个新项目中重新创建了它，其中我所做的就是安装 prism/prism.unityextensions，设置 shell 和视图，并将视图加载到 shell 区域中。这两个 xaml 文件背后的代码中都没有任何内容。

Shell

<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>

View1

<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}"应该足以设定焦点。

As per 焦点管理器文档 -

逻辑焦点属于 FocusManager.FocusedElement 内 具体的重点范围。

So, its 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。所以你能做的就是创建一个attach behaviour如同FocusManager.FocusedElement这将set keyboard focus on an element.

您可以参考此使用附加行为设置键盘焦点 -在 WPF 中设置键盘焦点.

该文章中的代码 -

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>