Question

我已动态将Canvas上的用户控件作为VisualTree控件中的Thumb根。我可以正确地移动拇指控件，但只能在从用户控件中定义的东，东南和南方矩形调整大小时正确地重新调整控件的大小。

//Instantiate a new Thumb control to be placed on the canvas.
var myThumb = new Thumb();
myThumb.Name = "myThumb";

//Instantiate a new ThumbTemplate and ElementFactory with my user control.
var myThumbTemplate = new ControlTemplate(typeof(Thumb));
myThumbTemplate.VisualTree = new FrameworkElementFactory(typeof(MyUserControl), "myUserControl");

//Set the thumb template to the newly instantiated template.
myThumb.Template = myThumbTemplate;

//Point the DragDelta and DragCompleted events to local methods.
myThumb.DragDelta += new DragDeltaEventHandler(myThumb_DragDelta);
myThumb.DragCompleted += new DragCompletedEventHandler(myThumb_DragCompleted);

//Add the thumb to the canvas control.
this.myCanvas.Children.Add(myThumb);
Canvas.SetZIndex(myThumb, 1);
Canvas.SetTop(myThumb, 75);
Canvas.SetLeft(myThumb, 50);

在DragDelta方法中，此方法可以从东部调整大小的矩形调整用户控件的大小：

var myThumb = sender as Thumb;
if (myThumb != null)
{
    var myUserControl = myThumb.Template.FindName("myUserControl", myThumb) as MyUserControl;
    if (myUserControl != null)
    {
        myUserControl.Width = myUserControl.OldWidth + e.HorizontalChange;
    } 
}

但无论我在哪里尝试这样做，另外设置Canvas.Top控件的Thumb（即来自北方重新调整大小的矩形），我得不到我预期的结果：

double top = Canvas.GetTop(finderThumb) + e.VerticalChange;
myUserControl.Height = myUserControl.OldHeight - e.VerticalChange;
Canvas.SetTop(myThumb, top);

然后发生的是控件在画布控件中上下移动，但只能按一个像素重新调整大小，无论垂直或水平变化如何。关于为什么会发生这种情况的任何想法以及解决问题的建议？谢谢！

Answer 1

尝试使用此示例中解释的此类（ResizeThumb） WPF Diagram Designer: Part 1

public class ResizeThumb : Thumb
{
    public ResizeThumb()
    {
        DragDelta += new DragDeltaEventHandler(this.ResizeThumb_DragDelta);
    }    

    private void ResizeThumb_DragDelta(object sender, DragDeltaEventArgs e)
    {
        Control item = this.DataContext as Control;
        if (item != null)
        {
            double deltaVertical, deltaHorizontal;

            switch (VerticalAlignment)
            {
                case VerticalAlignment.Bottom:
                    deltaVertical = Math.Min(-e.VerticalChange, 
                        item.ActualHeight - item.MinHeight);
                    item.Height -= deltaVertical;
                    break;
                case VerticalAlignment.Top:
                    deltaVertical = Math.Min(e.VerticalChange, 
                        item.ActualHeight - item.MinHeight);
                    Canvas.SetTop(item, Canvas.GetTop(item) + deltaVertical);
                    item.Height -= deltaVertical;
                    break;
                default:
                    break;
            }

            switch (HorizontalAlignment)
            {
                case HorizontalAlignment.Left:
                    deltaHorizontal = Math.Min(e.HorizontalChange, 
                        item.ActualWidth - item.MinWidth);
                    Canvas.SetLeft(item, Canvas.GetLeft(item) + deltaHorizontal);
                    item.Width -= deltaHorizontal;
                    break;
                case HorizontalAlignment.Right:
                    deltaHorizontal = Math.Min(-e.HorizontalChange, 
                        item.ActualWidth - item.MinWidth);
                    item.Width -= deltaHorizontal;
                    break;
                default:
                    break;
            }
        }
        e.Handled = true;
    }
}

Answer 2

从MSDN抓取的这个示例显示它添加e.VerticalChange而不是减去。也许这就是问题？

void onDragDelta(object sender, DragDeltaEventArgs e)
{
    //Move the Thumb to the mouse position during the drag operation
    double yadjust = myCanvasStretch.Height + e.VerticalChange;
    double xadjust = myCanvasStretch.Width + e.HorizontalChange;
    if ((xadjust >= 0) && (yadjust >= 0))
    {
        myCanvasStretch.Width = xadjust;
        myCanvasStretch.Height = yadjust;
        Canvas.SetLeft(myThumb, Canvas.GetLeft(myThumb) +
                                e.HorizontalChange);
        Canvas.SetTop(myThumb, Canvas.GetTop(myThumb) +
                                e.VerticalChange);
        changes.Text = "Size: " +
                        myCanvasStretch.Width.ToString() +
                         ", " +
                        myCanvasStretch.Height.ToString();
    }
}

在WPF中调整画布上的Thumb模板控件的大小

2 个答案: