c# – 启动器如何确定拖动已结束？

2023年9月14日 163次阅读

我们假设以下情况：

控件(例如,按钮)具有附加行为以启用拖放操作

<Button Content="test"> 
    <i:Interaction.Behaviors>
        <SimpleDragBehavior/>
    </i:Interaction.Behaviors>
</Button>

和SimpleDragBehavior

public class SimpleDragBehavior: Behavior<Button>
{       
    protected override void OnAttached ()
    {           
        AssociatedObject.MouseLeftButtonDown += OnAssociatedObjectMouseLeftButtonDown;
        AssociatedObject.MouseLeftButtonUp   += OnAssociatedObjectMouseLeftButtonUp;
        AssociatedObject.MouseMove           += OnAssociatedObjectMouseMove;

        mouseIsDown = false;
    }       

    private bool  mouseIsDown;

    private void OnAssociatedObjectMouseMove (object sender, MouseEventArgs e)
    {
        if (mouseIsDown)
        {
            AssociatedObject.Background = new SolidColorBrush(Colors.Red);

            DragDrop.DoDragDrop((DependencyObject)sender,
                                AssociatedObject.Content,
                                DragDropEffects.Link);
        }
    }

    private void OnAssociatedObjectMouseLeftButtonUp (object sender, MouseButtonEventArgs e)
    {
        mouseIsDown = false;
    }

    private void OnAssociatedObjectMouseLeftButtonDown (object sender, MouseButtonEventArgs e)
    {
        mouseIsDown = true;
    }       
}

现在的任务是确定拖动何时结束,以恢复按钮的原始背景.
在跌落目标上下潜时没问题.但是,我如何认识到某些不是下降目标的东西呢？在最糟糕的情况下：在窗外？

最佳答案 DragDrop.DoDragDrop在完成拖放操作后返回.

是的,“启动拖放操作”令人困惑,因为它可以被读作“开始拖放并返回”：

private void OnAssociatedObjectMouseMove (object sender, MouseEventArgs e)
{
    if (mouseIsDown)
    {
        AssociatedObject.Background = new SolidColorBrush(Colors.Red);

        var effects = DragDrop.DoDragDrop((DependencyObject)sender,
                            AssociatedObject.Content,
                            DragDropEffects.Link);

        // this line will be executed, when drag/drop will complete:
        AssociatedObject.Background = //restore color here;

        if (effects == DragDropEffects.None)
        {
            // nothing was dragged
        }
        else
        {
            // inspect operation result here
        }
    }
}
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