[英]How do I get mouse positions in my view model
根據MVVM設計模式,視圖模型不應了解視圖。 但就我而言,我需要視圖和模型,我的意思是:
在我的窗口中,有一個圖像組件。 當鼠標移到Image組件上並將其保存到模型中時,我想獲取鼠標位置。
后面的代碼是:
void Foo_MouseMove(objet sender, MouseEventArgs e)
{
model.x = e.getPosition(this.imageBox).X;
model.y = e.getPosition(this.imageBox).Y;
}
問題是:我需要this.imageBox和MouseEventArgs,所以需要兩個View元素。
我的問題是:如何使用MVVM方法處理這種情況?
我使用MVVM light框架
我將在此處使用附加行為。 這將使您能夠連續監視鼠標位置,而不是簡單地響應諸如MouseDown之類的事件。 您需要添加對System.Windows.Interactivity
程序集的引用。
下面的代碼提供了一個實際的簡單示例。
XAML
<Window x:Class="MouseMoveMvvm.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
xmlns:mouseMoveMvvm="clr-namespace:MouseMoveMvvm"
Title="MainWindow" Height="350" Width="525">
<Grid>
<DockPanel>
<StackPanel DockPanel.Dock="Top" Orientation="Horizontal">
<TextBlock Text="{Binding PanelX, StringFormat='X={0}'}" />
<TextBlock Text="{Binding PanelY, StringFormat='y={0}'}" />
</StackPanel>
<Canvas DockPanel.Dock="Bottom" Background="Aqua">
<i:Interaction.Behaviors>
<mouseMoveMvvm:MouseBehaviour MouseX="{Binding PanelX, Mode=OneWayToSource}" MouseY="{Binding PanelY, Mode=OneWayToSource}" />
</i:Interaction.Behaviors>
</Canvas>
</DockPanel>
</Grid>
</Window>
請注意,在上述XAML中,MouseBehaviour通過OneWayToSource綁定將鼠標位置向下推到ViewModel,而兩個TextBlocks從ViewModel讀取鼠標位置。
視圖模型
public class MainWindowViewModel : INotifyPropertyChanged
{
private double _panelX;
private double _panelY;
public event PropertyChangedEventHandler PropertyChanged;
public double PanelX
{
get { return _panelX; }
set
{
if (value.Equals(_panelX)) return;
_panelX = value;
OnPropertyChanged();
}
}
public double PanelY
{
get { return _panelY; }
set
{
if (value.Equals(_panelY)) return;
_panelY = value;
OnPropertyChanged();
}
}
[NotifyPropertyChangedInvocator]
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
var handler = PropertyChanged;
if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
}
}
依附行為
public class MouseBehaviour : System.Windows.Interactivity.Behavior<FrameworkElement>
{
public static readonly DependencyProperty MouseYProperty = DependencyProperty.Register(
"MouseY", typeof (double), typeof (MouseBehaviour), new PropertyMetadata(default(double)));
public double MouseY
{
get { return (double) GetValue(MouseYProperty); }
set { SetValue(MouseYProperty, value); }
}
public static readonly DependencyProperty MouseXProperty = DependencyProperty.Register(
"MouseX", typeof(double), typeof(MouseBehaviour), new PropertyMetadata(default(double)));
public double MouseX
{
get { return (double) GetValue(MouseXProperty); }
set { SetValue(MouseXProperty, value); }
}
protected override void OnAttached()
{
AssociatedObject.MouseMove += AssociatedObjectOnMouseMove;
}
private void AssociatedObjectOnMouseMove(object sender, MouseEventArgs mouseEventArgs)
{
var pos = mouseEventArgs.GetPosition(AssociatedObject);
MouseX = pos.X;
MouseY = pos.Y;
}
protected override void OnDetaching()
{
AssociatedObject.MouseMove -= AssociatedObjectOnMouseMove;
}
}
最后使用EventConverter找到了答案:
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;
}
}
這個轉換器使我可以處理Point而不是圖形組件。
XML來了:
<i:Interaction.Triggers>
<i:EventTrigger EventName="MouseMove">
<cmd:EventToCommand
Command="{Binding Main.MouseMoveCommand, Mode=OneWay}"
EventArgsConverter="{StaticResource MouseButtonEventArgsToPointConverter}"
EventArgsConverterParameter="{Binding ElementName=Image1}"
PassEventArgsToCommand="True" />
</i:EventTrigger>
</i:Interaction.Triggers>
Mark Greens解決方案是最好的(我發現)。
如果要使他的解決方案可用於任何WPF控件(我建議),則從System.Windows.Interactivity.Behavior<Control>
繼承實際上不適用於Panel
,因為Panel
不能從Control
繼承。 僅那些類從Control
繼承: https : //msdn.microsoft.com/de-de/library/system.windows.controls.control(v=vs.110).aspx
而是從System.Windows.Interactivity.Behavior<FrameworkElement>
繼承。 FrameworkElement
是所有WPF控件類的始祖: https : //msdn.microsoft.com/de-de/library/system.windows.frameworkelement(v=vs.110).aspx 。 我已經在Grid
, Panel
和Image
btw上對其進行了測試。
我使用它使彈出窗口與鼠標光標保持同步:
<Image x:Name="Image1">
<i:Interaction.Behaviors>
<myNamespace:MouseBehaviour
MouseX="{Binding ElementName=Popup1, Path=HorizontalOffset, Mode=OneWayToSource}"
MouseY="{Binding ElementName=Popup1, Path=VerticalOffset, Mode=OneWayToSource}">
</myNamespace:MouseBehaviour>
</i:Interaction.Behaviors>
</Image>
<Popup x:Name="Popup1" PlacementTarget="{Binding ElementName=Image1}"/>
PS:我會對解決方案發表評論,但是我的回答太長了。
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