c# - WPF 用鼠标移动元素

Question

我正在尝试在 WPF 应用程序中使用鼠标移动按钮。

XAML Grid 是结构的根:

<Grid Name="MyGrid"            >
    <Button Name="Samplebutton"
            PreviewMouseDown="Samplebutton_PreviewMouseDown"
            PreviewMouseUp="Samplebutton_PreviewMouseUp"
            PreviewMouseMove="Samplebutton_PreviewMouseMove"
            Content="Moving" Width="100" Height="35"/>
</Grid>

和代码背后:

private bool _isMoving;


private void Samplebutton_PreviewMouseDown(object sender, MouseButtonEventArgs e)
{
    _isMoving = true;
}

private void Samplebutton_PreviewMouseUp(object sender, MouseButtonEventArgs e)
{
    _isMoving = false;
}

private void Samplebutton_PreviewMouseMove(object sender, MouseEventArgs e)
{
    if (!_isMoving) return;

    TranslateTransform transform = new TranslateTransform();
    transform.X = Mouse.GetPosition(MyGrid).X;
    transform.Y = Mouse.GetPosition(MyGrid).Y;
    this.Samplebutton.RenderTransform = transform;
}

首先点击按钮将他移远，然后我可以移动按钮，但第一次按钮被移开。我缺少什么？

Answer 1

以下是您问题的完整解决方案:

private bool _isMoving;
private Point? _buttonPosition;
private double deltaX;
private double deltaY;
private TranslateTransform _currentTT;

private void Samplebutton_PreviewMouseDown(object sender, MouseButtonEventArgs e)
{
    if(_buttonPosition == null)
        _buttonPosition = Samplebutton.TransformToAncestor(MyGrid).Transform(new Point(0, 0));
    var mousePosition = Mouse.GetPosition(MyGrid);
    deltaX = mousePosition.X - _buttonPosition.Value.X;
    deltaY = mousePosition.Y - _buttonPosition.Value.Y;
    _isMoving = true;
}

private void Samplebutton_PreviewMouseUp(object sender, MouseButtonEventArgs e)
{
    _currentTT = Samplebutton.RenderTransform as TranslateTransform;
    _isMoving = false;
}

private void Samplebutton_PreviewMouseMove(object sender, MouseEventArgs e)
{
    if (!_isMoving) return;

    var mousePoint = Mouse.GetPosition(MyGrid);

    var offsetX = (_currentTT == null ?_buttonPosition.Value.X : _buttonPosition.Value.X - _currentTT.X) + deltaX - mousePoint.X;
    var offsetY = (_currentTT == null ? _buttonPosition.Value.Y : _buttonPosition.Value.Y - _currentTT.Y) + deltaY - mousePoint.Y;

    this.Samplebutton.RenderTransform = new TranslateTransform(-offsetX, -offsetY);
}