如何围绕按钮点击文本框的 [英] How to Focus an TextBox on Button click

问题描述

因此，如何使用MVVM模式的按钮点击焦点的文本框

So how to Focus an TextBox on Button click using the MVVM Pattern?

我基础上的这个答案这适用于第一次点击，但之后不设置对焦了。我怀念什么？

i created an simple Testproject Based on this Answer which works on the first click, but after that it doesn't set the Focus anymore. What do i miss?

XAML（视图）

<Grid>
    <TextBox Height='23' HorizontalAlignment='Left' Margin='12,12,0,0' VerticalAlignment='Top' Width='120'
             Text='{Binding TheText}'
             local:FocusExtension.IsFocused="{Binding IsFocused}"/>
    <Button Content='Click' Height='23' HorizontalAlignment='Left' Margin='138,11,0,0' VerticalAlignment='Top' Width='75' 
            Command='{Binding ClickCommand}'/>
    <Button Content='Just to deFocus' Height='28' HorizontalAlignment='Left' Margin='14,44,0,0' Name='button1' VerticalAlignment='Top' Width='199' />
</Grid>

视图模型

public class ViewModel : INotifyPropertyChanged
{
    public string TheText { get; set; }
    public bool IsFocused { get; set; }

    private RelayCommand _clickCommand;
    public ICommand ClickCommand
    {
        get { return _clickCommand ?? (_clickCommand = new RelayCommand(param => this.OnClick())); }
    }
    private void OnClick()
    {
        IsFocused = true;
        RaisePropertyChanged("IsFocused");
    }

    #region INotifyPropertyChanged

    public event PropertyChangedEventHandler PropertyChanged;

    public void RaisePropertyChanged(string propName)
    {
        if (this.PropertyChanged != null)
            this.PropertyChanged(this, new PropertyChangedEventArgs(propName));
    }

    #endregion
}

和这里是一个具有蓄势待发项目（VS2010的下载链接 ）为懒惰的;）

and here is an Download link with an ready to go Project(VS2010) for the lazy ones ;)

推荐答案

初始默认后，您的附加属性值永远不会回false被覆盖。因此，你的 FocusExtension 类不叫焦点（）在文本框因为的PropertyChanged 并不需要在你的虚拟机真正的 IsFocused 设置时开火。

Your attached property value is never going back to false after the initial default is overwritten. hence your FocusExtension class is not calling Focus() on the TextBox since the PropertyChanged does not need to fire when setting IsFocused in your VM to true.

切换 OnIsFocusedPropertyChanged（...）

从：

private static void OnIsFocusedPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
    var uie = (UIElement)d;
    if ((bool)e.NewValue)
        uie.Focus(); // Don't care about false values.
}

到

to

private static void OnIsFocusedPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) {
  var uie = (UIElement)d;
  if (!((bool)e.NewValue))
    return;
  uie.Focus();
  uie.LostFocus += UieOnLostFocus;
}

private static void UieOnLostFocus(object sender, RoutedEventArgs routedEventArgs) {
  var uie = sender as UIElement;
  if (uie == null)
    return;
  uie.LostFocus -= UieOnLostFocus;
  uie.SetValue(IsFocusedProperty, false);
}

更新：

随着上述变化也确保

地方：FocusExtension.IsFocused ={结合IsFocused}

切换到

地方：FocusExtension.IsFocused ={结合IsFocused，模式=双向}

的工作下载链接

另一个更新

要设置模式=双向在 FocusExtension 级交换机默认此附加属性

To set the Mode=TwoWay as default for this attached property in FocusExtension class switch

public static readonly DependencyProperty IsFocusedProperty = DependencyProperty.RegisterAttached(
  "IsFocused",
  typeof(bool),
  typeof(FocusExtension),
  new UIPropertyMetadata(
    false,
    OnIsFocusedPropertyChanged));

到

to

public static readonly DependencyProperty IsFocusedProperty = DependencyProperty.RegisterAttached(
  "IsFocused",
  typeof(bool),
  typeof(FocusExtension),
  new FrameworkPropertyMetadata(
    false,
    FrameworkPropertyMetadataOptions.BindsTwoWayByDefault,
    OnIsFocusedPropertyChanged));

您可以跳过显式指定模式=双向在上述声明中的XAML。

You can skip explicitly specifying Mode=TwoWay in xaml with the above declaration.

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