2.WPF 自定义控件封装对象的命令属性2024-05-15

无法绑定的属性, 通过附加属性扩展

Xaml页面部分

 <e:EventExtension.EventTarget>
     <e:EventCommand EventName="PreviewMouseLeftButtonDown"
                     Command="{Binding PreBtnCommand}"
                     CommandParameter="123">
     </e:EventCommand>
 </e:EventExtension.EventTarget>

cs代码部分

public class EventExtension
{
    public static EventCommand GetEventTarget(DependencyObject obj)
    {
        return (EventCommand)obj.GetValue(EventTargetProperty);
    }

    public static void SetEventTarget(DependencyObject obj, EventCommand value)
    {
        obj.SetValue(EventTargetProperty, value);
    }

    public static readonly DependencyProperty EventTargetProperty =
        DependencyProperty.RegisterAttached(
            "EventTarget", typeof(EventCommand),
            typeof(EventExtension),
            new PropertyMetadata(null, new PropertyChangedCallback(OnEventTargetChanged)));

    private static void OnEventTargetChanged(
        DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        // 可以拿到 事件名称    Command
        var ec = (e.NewValue as EventCommand);

        EventInfo ei = d.GetType().GetEvent(ec.EventName);

        // 动态挂载事件
        var handler = Delegate.CreateDelegate(
             ei.EventHandlerType,
             typeof(EventExtension).GetMethod("EventExecute",
                     BindingFlags.NonPublic | BindingFlags.Static));

        ei.AddEventHandler(d, handler);

    }

    private static void EventExecute(object sender, EventArgs e)
    {
        // 事件转命令
        var ec = GetEventTarget((DependencyObject)sender);
        // 如果Command获取为null，有可能是因为EventCommand对象的继承有问题，需要继承Animatable
        if (ec.CommandParameter == null)
        {
            ec.Command?.Execute(e);
        }
        else
            ec.Command?.Execute(ec.CommandParameter);
    }


    // 尝试：事件方法编写在VM中，然后在页面上进行指定，如何处理？
}

public class EventCommand : Animatable
{
    public string EventName { get; set; }


    public ICommand Command
    {
        get { return (ICommand)GetValue(CommandProperty); }
        set { SetValue(CommandProperty, value); }
    }

    public static readonly DependencyProperty CommandProperty =
        DependencyProperty.Register("Command", typeof(ICommand), typeof(EventCommand), new PropertyMetadata(null));



    public object CommandParameter
    {
        get { return (object)GetValue(CommandParameterProperty); }
        set { SetValue(CommandParameterProperty, value); }
    }

    public static readonly DependencyProperty CommandParameterProperty =
        DependencyProperty.Register("CommandParameter", typeof(object), typeof(EventCommand), new PropertyMetadata(null));


    protected override Freezable CreateInstanceCore()
    {
        return (Freezable)Activator.CreateInstance(GetType());
    }
}