Question

我有一个用户控件，我在网格中拖动。 Z-Index设置得相当高，以便我可以将它保持在其他孩子之上。拖动控件可以很好地工作，但如果用户想要将控件移出网格外，它将允许它。

如何防止它离开父网格控件的边界，这就是我现在所拥有的：

   private System.Windows.Point _anchorPoint;
    private System.Windows.Point _currentPoint;
    private bool _isInDrag;

   private void UserControl_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
        var element = sender as FrameworkElement;
        _anchorPoint = e.GetPosition(null);
        if (element != null) element.CaptureMouse();
        _isInDrag = true;
        e.Handled = true;
    }

    private void UserControl_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
    {
        if (!_isInDrag) return;
        var element = sender as FrameworkElement;
        if (element != null) element.ReleaseMouseCapture();
        _isInDrag = false;
        e.Handled = true;
    }

   private void UserControl_MouseMove(object sender, MouseEventArgs e)
        {
            if (!_isInDrag) return;
            _currentPoint = e.GetPosition(null);

            UIElement container = VisualTreeHelper.GetParent(_parentGrid) as UIElement;
            System.Windows.Point relativeLocation = _parentGrid.TranslatePoint(new System.Windows.Point(0, 0), container);

            if (_currentPoint.X > relativeLocation.X) return;
            if(_currentPoint.Y >= relativeLocation.Y)return;

            _transform.X += _currentPoint.X - _anchorPoint.X;
            _transform.Y += (_currentPoint.Y - _anchorPoint.Y);
            RenderTransform = _transform;
            _anchorPoint = _currentPoint;
        }

＆＃34; relativeLocation＆＃34;总是0x0，所以这不起作用。任何想法将不胜感激。

*注意：我知道如果我将UserControl更改为Window，它将减轻我遇到的所有问题。但说实话，它看起来很棒，而且我真的不想让窗户混乱。该系统以仪表板的形式打开，消耗了用户的信息。整个窗口（在单独的窗口上打开）。所以当你在这里打开一个窗口时，它不会向右流动。

Answer 1

我认为你不需要relativeLocation。不过，数学可能有点烦人。尝试这种方法，当我测试它时效果很好：

    private void UserControl_MouseMove(object sender, MouseEventArgs e)
    {
        if (!_isInDrag) return;
        _currentPoint = e.GetPosition(null);

        //This is the change to the position that we want to apply
        Point delta = new Point();
        delta.X = _currentPoint.X - _anchorPoint.X;
        delta.Y = _currentPoint.Y - _anchorPoint.Y;

        //Calculate user control edges
        var leftEdge   = Margin.Left + _transform.X + delta.X;
        var topEdge    = Margin.Top + _transform.Y + delta.Y;
        var rightEdge  = Width + Margin.Left + _transform.X + delta.X;
        var bottomEdge = Height + Margin.Top + _transform.Y + delta.Y;

        //Set the delta to 0 if it goes over _parentGrid edges
        if (leftEdge < 0) delta.X = 0;
        if (topEdge  < 0) delta.Y = 0;

        if (rightEdge  > _parentGrid.Width)  delta.X = 0;
        if (bottomEdge > _parentGrid.Height) delta.Y = 0;

        //Apply the delta to the user control
        _transform.X += delta.X;
        _transform.Y += delta.Y;
        RenderTransform = _transform;
        _anchorPoint = _currentPoint;
    }

Answer 2

这是一个开始：

Point position = _parentGrid.PointToScreen(new Point(0, 0));
PresentationSource source = PresentationSource.FromVisual(_parentGrid);
position = source.CompositionTarget.TransformFromDevice.Transform(position);

现在您拥有父网格的屏幕坐标。调用Transform()很重要，因为它会将像素转换为与WPF设备无关的像素，与系统DPI设置相匹配。

拖动用户控件，但将其保留在WPF

2 个答案: