WPF如何在缩放过程中阻止滚动查看器上下移动

Question

我在ScrollViewer里面有一个Grid。我为网格设置了一个长高度。

动态地，我添加一个Canvas到我的网格，并在它里面添加2个矩形。鼠标缩放事件正在工作，但当我启动应用程序并向下滚动到2个框的末端，我尝试用鼠标缩放时，滚动查看器上升到其起始位置。我不想禁用它，我想让它一直显示但不上移。

• MainWindow.xaml

<ScrollViewer VerticalScrollBarVisibility="Visible" HorizontalScrollBarVisibility="Visible" Name="sv">
<Grid Name="myGrid">
<Grid.RowDefinitions>
<RowDefinition Height="50" />
<RowDefinition Height="5000" />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="330" />
</Grid.ColumnDefinitions>
</Grid>
</ScrollViewer>

• MainWindow.xaml.cs

public partial class MainWindow : Window
{
double currentZoom = 0;
ScaleTransform scaleTransform;
TransformGroup transformGroup;
public MainWindow()
{
InitializeComponent();
scaleTransform = new ScaleTransform();
transformGroup = new TransformGroup();
transformGroup.Children.Add(scaleTransform);
begin();
}
private void begin()
{
Canvas canvas = new Canvas();
Rectangle rectangle1 = new Rectangle
{
Width = 300,
Height = 600,
Fill = new SolidColorBrush(Color.FromRgb(255, 255, 255)),
StrokeThickness = 2,
Stroke = Brushes.Black
};
Canvas.SetLeft(rectangle1, 100);
Canvas.SetTop(rectangle1, 100);
canvas.Children.Add(rectangle1);
Rectangle rectangle2 = new Rectangle
{
Width = 300,
Height = 600,
Fill = new SolidColorBrush(Color.FromRgb(255, 255, 255)),
StrokeThickness = 2,
Stroke = Brushes.Black
};
Canvas.SetLeft(rectangle2, 200);
Canvas.SetTop(rectangle2, 200);
canvas.Children.Add(rectangle2);
myGrid.Children.Add(canvas);
myGrid.RenderTransform = transformGroup;
myGrid.MouseWheel += (sender, e) => wheelEvent(sender, e);
}
private void wheelEvent(object sender, MouseWheelEventArgs e)
{
Point position = e.GetPosition(myGrid);
scaleTransform.CenterX = position.X;
scaleTransform.CenterY = position.Y;
var newZoom = e.Delta / 120 / (double)50;
scaleTransform.ScaleX = 1 + newZoom + currentZoom;
scaleTransform.ScaleY = 1 + newZoom + currentZoom;
currentZoom += newZoom;
}
}

Answer 1

你可以使用MouseWheelEventArgs。属性来阻止其他事件处理程序执行它们的操作。

private void wheelEvent(object sender, MouseWheelEventArgs e)
{
//Might be a good idea to use some custom condition
//that determines if you are zooming or not like:
//if(!IsCtrlButtonPressed) return;
//If you return with e.Handled == false 
//ScrollViewer's handler will scroll you normally
//suppress MouseWheel event and other MouseWheel responders
e.Handled = true;
//your zooming logic
}

更多信息在这里:MSDN