如何将焦点添加到 WPF 中的可编辑组合框 [英] How to add a focus to an editable ComboBox in WPF

问题描述

我在 wpf 中使用了一个可编辑的 ComboBox，但是当我尝试从 C# 代码设置焦点时，它只显示选择.但我想选择编辑选项(光标应显示以供用户输入).

I am using an editable ComboBox in wpf but when i try to set focus from C# code, it is only shows selection. but i want to go for edit option (cursor should display for user input).

推荐答案

您可以尝试从 ComboBox 派生并访问内部 TextBox，如下所示:

You might try deriving from ComboBox and access the internal TextBox, like this:

public class MyComboBox : ComboBox
{
    TextBox _textBox;

    public override void OnApplyTemplate()
    {
        base.OnApplyTemplate();

        _textBox = Template.FindName("PART_EditableTextBox", this) as TextBox;
        if (_textBox != null)
        {
            _textBox.GotKeyboardFocus += _textBox_GotFocus;
            this.Unloaded += MyComboBox_Unloaded;
        }
    }

    void MyComboBox_Unloaded(object sender, System.Windows.RoutedEventArgs e)
    {
        _textBox.GotKeyboardFocus -= _textBox_GotFocus;
        this.Unloaded -= MyComboBox_Unloaded;
    }

    void _textBox_GotFocus(object sender, System.Windows.RoutedEventArgs e)
    {
        _textBox.Select(_textBox.Text.Length, 0); // set caret to end of text
    }

}

在您的代码中，您会像这样使用它:

In your code you would use it like this:

<Window x:Class="EditableCbox.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:EditableCbox"
    Title="Window1" Height="300" Width="300">
    ...
        <local:MyComboBox x:Name="myComboBox" IsEditable="True" Grid.Row="0" Margin="4">
            <ComboBoxItem>Alpha</ComboBoxItem>
            <ComboBoxItem>Beta</ComboBoxItem>
            <ComboBoxItem>Gamma</ComboBoxItem>
        </local:MyComboBox>
    ...
</Window>

然而，这个解决方案有点危险，因为在即将推出的 WPF 版本中，Microsoft 可能还会决定添加 GotKeyboardFocus 事件处理程序(或类似的事件处理程序)，这可能会与 MyComboBox 中的事件处理程序发生冲突.

This solution slightly dangerous, however, because in upcoming versions of WPF, Microsoft might decide also to add a GotKeyboardFocus event handler (or similar event handlers), which might get in conflict in with the event handler in MyComboBox.

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