Question

短：在调用myModel.InvalidatePlot（true / false）更新模型后，OxyPlot鼠标事件处理程序（例如mySeries.MouseDown）在一瞬间没有被捕获。

详细：我以一种非传统的方式使用OxyPlot库。我正在模仿在后台播放视频，快速更新占据整个图形的图像注释。这允许我使用鼠标事件在图像上绘图。我的问题是视频/图像注释播放和鼠标事件分开工作，但是当“框架更新”期间发生鼠标事件时。其中一些人错过了。我的信念是，当绘图无效myModel.InvalidatePlot（true / false）时，在模型更新之前不会拾取鼠标事件。

Answer 1

我发现InvalidatePlot导致PlotView从未捕获鼠标按钮事件（例如OnMouseDown（MouseButtonEventArgs e））的问题。为了解决这个问题，我使用了另一个WPF对象来捕获鼠标事件并强制调用我的PlotView的鼠标处理方法：

1）我在另一个ZIndex级别添加了WPF Grid。并附加到鼠标事件（MouseDown，MouseWheel等）的函数：

<Grid x:Name="Grid_MouseCatcher"
        HorizontalAlignment="Stretch"
        VerticalAlignment="Stretch"
        Panel.ZIndex="2"
        MouseDown="Grid_MouseCatcher_MouseDown"
        MouseEnter="Grid_MouseCatcher_MouseEnter"
        MouseLeave="Grid_MouseCatcher_MouseLeave"
        MouseMove="Grid_MouseCatcher_MouseMove"
        MouseUp="Grid_MouseCatcher_MouseUp"
        MouseWheel="Grid_MouseCatcher_MouseWheel"
        Opacity="0.0"
        PreviewMouseMove="SetFocusToOxyPlot" />
<oxy:PlotView x:Name="PlotView"
        HorizontalContentAlignment="Stretch"
        VerticalContentAlignment="Stretch"
        Panel.ZIndex="1"
        Model="{Binding PlotModel}" />

2）网格处理的每个事件都会调用我在OxyPlot源代码中创建的公共方法：

 /// <summary>
 /// Sends mouse events from the overlaying grid to the PlotView. Forcing an Action.
 /// This was included due to an OxyPlot bug where the OnMouse... methods were not being called 
 /// when the plot was invalidated via InvalidatePlot(...)
 /// </summary>
 /// <param name="sender"></param>
 /// <param name="e"></param>
 private void Grid_MouseCatcher_MouseDown(object sender, MouseButtonEventArgs e)
 {
     Debug.WriteLine("MouseCatcher - Down: " + e.GetPosition(Grid_MouseCatcher).X + " " + e.GetPosition(Grid_MouseCatcher).Y);
     PlotView.ForceMouseDown(e);
 }

3）在源代码文件 OxyPlot.Wpf \ PlotBase.Events.cs 中我创建了一些函数（例如ForceMouseDown（MouseButtonEventArgs e）），它们显式调用受保护的鼠标事件（OnMouseDown（MouseButtonEventArgs e）））

/// <summary>
/// Forces a call to Mouse handler. 
/// This was needed because the events were getting lost when the model was updating
/// </summary>
/// <param name="e"></param>
/// <returns></returns>
public void ForceMouseDown(MouseButtonEventArgs e){
    this.OnMouseDown(e);
}


/// <summary>
/// Invoked when an unhandled MouseDown attached event reaches an element in its route that is derived from this class. 
/// Implement this method to add class handling for this event.
/// </summary>
/// <param name="e">The <see cref="T:System.Windows.Input.MouseButtonEventArgs" /> that contains the event data. 
/// This event data reports details about the mouse button that was pressed and the handled state.</param>
protected override void OnMouseDown(MouseButtonEventArgs e)
{
    base.OnMouseDown(e);
    if (e.Handled)
    {
        return;
    }

    this.Focus();
    this.CaptureMouse();

    // store the mouse down point, check it when mouse button is released to determine if the context menu should be shown
    this.mouseDownPoint = e.GetPosition(this).ToScreenPoint();

    e.Handled = this.ActualController.HandleMouseDown(this, e.ToMouseDownEventArgs(this));
}

通过这种方式修复问题，我仍然可以按照OxyPlot建议的方式将鼠标事件处理程序添加到我的Plotview中，因为它们的OnMouse ####事件仍然被调用，它们现在只是由覆盖网格显式调用。 / p>

Answer 2

我找到了一个更简单的解决方案，基于CodyF的解决方案。在OxyPlot.Wpf.PlotBase中的OnApplyTemplate（）末尾添加以下行：

var mouseGrid = new Grid();
mouseGrid.Background = Brushes.Transparent; // background must be set for hit test to work
this.grid.Children.Add(mouseGrid);

然而，这种变化目前会制动工具提示。另请参阅OxyPlot的github页面中的pull request。

模型无效时，不会捕获Oxyplot的鼠标事件

2 个答案: