从转换器获取值到视图模型

Question

我的目标是在鼠标移过给定网格时获取鼠标点位置。

XAML:

<UserControl.Resources>     
  <helpers:MouseButtonEventArgsToPointConverter x:Key="mConverter"/>
</UserControl.Resources>
...
<Grid DataContext="{Binding CartesianChartVM, Source={StaticResource Locator}}">
            <i:Interaction.Triggers>
                <i:EventTrigger EventName="MouseMove">
                    <i:InvokeCommandAction Command="{Binding MouseMoveCommand}"   CommandParameter="ThePoint"/>
                </i:EventTrigger>
                <i:EventTrigger EventName="MouseMove">
                    <cmd:EventToCommand
             Command="{Binding Main.MouseMoveCommand, Mode=OneWay}"
             EventArgsConverter="{StaticResource mConverter}"
             EventArgsConverterParameter="{Binding ElementName=ThePoint}"
             PassEventArgsToCommand="True" />
                </i:EventTrigger>
            </i:Interaction.Triggers>
</Grid>

其中：

xmlns:cmd="clr-namespace:GalaSoft.MvvmLight.Command;assembly=GalaSoft.MvvmLight.Platform"
xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"

转换器：

public class MouseButtonEventArgsToPointConverter : IEventArgsConverter
{
    public object Convert(object value, object parameter)
    {
        var args = (MouseEventArgs)value;
        var element = (FrameworkElement)parameter;
        var point = args.GetPosition(element);
        return point;
    }
}

视图模型：

    public ICommand MouseMoveCommand { get; private set; }
    private Point thePoint;

    public CartesianChartVM()
    {
        MouseMoveCommand = new RelayCommand(MouseMoveMethod);
    }
    void MouseMoveMethod()
    {
        Point p= ThePoint;
    }

    public Point ThePoint
    {
        get { return thePoint; }
        set
        {
            thePoint = value;
            RaisePropertyChanged("ThePoint");
        }
    }

If I put breakpoint inside the converter class I can see the point coordinates, but how can I get this point value to the view model when mousemove event occures.

I tried with Point ThePoint inside the view model but it's alwaws (0,0), How do I pass the point value fom the converter class to the view model class?

Answer 1

我刚刚使用了 xaml 中的 CallMethodAction。值得注意的是，我正在使用 in this blog post

中描述的新行为 NuGet 包

这是我的 xaml:

<Window x:Class="mousepointerTest.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:i="http://schemas.microsoft.com/xaml/behaviors"
    xmlns:local="clr-namespace:mousepointerTest"
    mc:Ignorable="d"
    Title="MainWindow" Height="450" Width="800"
    >
<Window.DataContext>
    <local:MainWindowViewModel />
</Window.DataContext>
<Grid>
    <DataGrid x:Name="TestGrid" 
              HorizontalAlignment="Stretch"
              VerticalAlignment="Stretch"
              BorderBrush="Black"
              BorderThickness="3">
        <i:Interaction.Triggers>
            <i:EventTrigger EventName="MouseMove">
                <i:CallMethodAction MethodName="OnMouseMove"
                                    TargetObject="{Binding}" />
            </i:EventTrigger>
        </i:Interaction.Triggers>
    </DataGrid>
</Grid>

这是我的 ViewModel：

public class MainWindowViewModel
{
    public void OnMouseMove(object sender, MouseEventArgs e)
    {
        var point = e.GetPosition((IInputElement)e.Source);
    }
}

这确实要求您知道传递的事件参数类型，否则您将收到方法签名匹配错误。

Answer 2

你接下来应该做的：

将网格背景设置为不透明。 wpf 中的透明对象不会缓存鼠标事件。 <Grid Background="#01FFFFFF">

为您的命令创建带有参数的方法

public ICommand DoSomething { get; private set; }

public TestVM()
{
    DoSomething = new RelayCommand<Point>(SomeAction);
}

private void SomeAction(Point point)
{

}

只保存一个触发器并使其看起来像那个：

 <i:Interaction.Triggers>
<i:EventTrigger EventName="MouseMove">
                <cmd:EventToCommand
             Command="{Binding DoSomething}"
             EventArgsConverter="{StaticResource mConverter}"
             PassEventArgsToCommand="True" />
            </i:EventTrigger>
        </i:Interaction.Triggers>

从转换器获取值到视图模型

Get the value from the converter to the view model

c#

wpf

xaml

mvvm-light