按钮单击后触发 WPF 附加行为

Question

我有以下在按钮单击事件中被调用的类/行为。问题是它在 button_click 事件之后被调用。如何在按钮单击事件之前调用它？ 下面提到的样式在 App.xaml 中定义以供全局使用

XAML：

<Style TargetType="Button">
        <Setter Property="local:DefaultButtonBehaviour.DefaultButton" Value="True" />
</Style>

代码：

public static class DefaultButtonBehaviour
{
    /// 1. This is the boolean attached property with its getter and setter:
    public static readonly DependencyProperty DefaultButtonProperty =
        DependencyProperty.RegisterAttached
        (
            "DefaultButton",
            typeof(bool),
            typeof(DefaultButtonBehaviour),
            new UIPropertyMetadata(false, OnDefaultButtonPropertyChanged)
        );
    public static bool GetDefaultButton(DependencyObject obj)
    {
        return (bool)obj.GetValue(DefaultButtonProperty);
    }
    private static void SetDefaultButton(DependencyObject obj, bool value)
    {
        obj.SetValue(DefaultButtonProperty, value);
    }

    /// 2. This is the change event of our attached property value:
    ///     * We get in the first parameter the dependency object to which the attached behavior was attached
    ///     * We get in the second parameter the value of the attached behavior.
    ///     * The implementation of the behavior is to check if we are attached to a textBox, and if so and the value of the behavior
    ///       is true, hook to the PreviewGotKeyboardFocus of the textbox.
    private static void OnDefaultButtonPropertyChanged(DependencyObject dpo, DependencyPropertyChangedEventArgs args)
    {
        ButtonBase button = dpo as ButtonBase;
        if (button != null)
        {
            if ((bool)args.NewValue)
            {
                button.Click += OnDefaultButtonClick;
            }
            else
            {
                button.Click -= OnDefaultButtonClick; ;
            }
        }
    }

    private static void OnDefaultButtonClick(object sender, RoutedEventArgs e)
    {
        ButtonBase btn = (ButtonBase)sender;
        DependencyObject focusScope = FocusManager.GetFocusScope(btn);
        FocusManager.SetFocusedElement(focusScope, btn);
        Keyboard.Focus(btn);
    }

}

Answer 1

如果我正确地回答了这个问题，您可以通过连接Preview 事件来解决这个问题。挂钩PreviewMouseDown 和PreviewKeyDown（这样您就可以处理用户使用返回键激活按钮的情况）。