如何在我的ViewModel中访问XAML对象？我真的很困惑。我想访问<Controls:ModalContentPresenter>对象。如何以MVVM整合方式实现这一点？我要在此对象上调用方法ShowModalContent
<Controls:ModalContentPresenter x:Name="modalContent">
<ScrollViewer Behaviors:AdvancedZooming.KeepInCenter="true" Visibility="{Binding LeerformularIsVisible}" HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto">
<Viewbox Stretch="Uniform">
<Grid>
<DataGrid BorderBrush="{x:Null}">
<DataGrid.ContextMenu>
<ContextMenu>
<MenuItem Command="{Binding AddFieldDefinitionCommand}" Header="Feld hinterlegen" Icon="pack://application:,,,/Images/Designer/field.png" />
<MenuItem Command="{Binding AddFunctionCommand}" Header="Funktion hinterlegen" Icon="pack://application:,,,/Images/Designer/FI_Taschenmesser_16x16.png" />
<MenuItem Command="{Binding RemoveFieldDefinitionCommand}" Header="Aktuelle Felddefinition entfernen" Icon="pack://application:,,,/Images/Designer/remove_field.png" />
<MenuItem Command="{Binding CutCommand}" Header="Ausschneiden" Icon="pack://application:,,,/Images/Zwischenablage/FI_Ausschneiden_16x16.png" />
<MenuItem Command="{Binding CopyCommand}" Header="Kopieren" Icon="pack://application:,,,/Images/Zwischenablage/FI_Kopieren_16x16.png" />
<MenuItem Command="{Binding PasteCommand}" Header="Einfügen" Icon="pack://application:,,,/Images/Zwischenablage/FI_Einfuegen_16x16.png" />
</ContextMenu>
</DataGrid.ContextMenu>
</DataGrid>
</Grid>
</Viewbox>
</ScrollViewer>
<Controls:ModalContentPresenter.ModalContent>
<StackPanel>
<TextBlock>Test</TextBlock>
<Button>Hide</Button>
</StackPanel>
</Controls:ModalContentPresenter.ModalContent>
</Controls:ModalContentPresenter>
ModalContentPresenter的代码可以在这里找到：
using System;
using System.Collections;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Markup;
using System.Windows.Media;
namespace Controls
{
[ContentProperty("Content")]
public class ModalContentPresenter : FrameworkElement
{
#region private fields
private Panel layoutRoot;
private ContentPresenter primaryContentPresenter;
private ContentPresenter modalContentPresenter;
private Border overlay;
private object[] logicalChildren;
private KeyboardNavigationMode cachedKeyboardNavigationMode;
private static readonly TraversalRequest traversalDirection;
#endregion
#region dependency properties
public static readonly DependencyProperty IsModalProperty = DependencyProperty.Register("IsModal", typeof(bool), typeof(ModalContentPresenter),
new FrameworkPropertyMetadata(false, FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, OnIsModalChanged));
public static readonly DependencyProperty ContentProperty = DependencyProperty.Register("Content", typeof(object), typeof(ModalContentPresenter),
new UIPropertyMetadata(null, OnContentChanged));
public static readonly DependencyProperty ModalContentProperty = DependencyProperty.Register("ModalContent", typeof(object), typeof(ModalContentPresenter),
new UIPropertyMetadata(null, OnModalContentChanged));
public static readonly DependencyProperty OverlayBrushProperty = DependencyProperty.Register("OverlayBrush", typeof(Brush), typeof(ModalContentPresenter),
new UIPropertyMetadata(new SolidColorBrush(Color.FromArgb(204, 169, 169, 169)), OnOverlayBrushChanged));
public bool IsModal
{
get { return (bool)GetValue(IsModalProperty); }
set { SetValue(IsModalProperty, value); }
}
public object Content
{
get { return (object)GetValue(ContentProperty); }
set { SetValue(ContentProperty, value); }
}
public object ModalContent
{
get { return (object)GetValue(ModalContentProperty); }
set { SetValue(ModalContentProperty, value); }
}
public Brush OverlayBrush
{
get { return (Brush)GetValue(OverlayBrushProperty); }
set { SetValue(OverlayBrushProperty, value); }
}
#endregion
#region routed events
public static readonly RoutedEvent PreviewModalContentShownEvent = EventManager.RegisterRoutedEvent("PreviewModalContentShown", RoutingStrategy.Tunnel,
typeof(RoutedEventArgs), typeof(ModalContentPresenter));
public static readonly RoutedEvent ModalContentShownEvent = EventManager.RegisterRoutedEvent("ModalContentShown", RoutingStrategy.Bubble,
typeof(RoutedEventArgs), typeof(ModalContentPresenter));
public static readonly RoutedEvent PreviewModalContentHiddenEvent = EventManager.RegisterRoutedEvent("PreviewModalContentHidden", RoutingStrategy.Tunnel,
typeof(RoutedEventArgs), typeof(ModalContentPresenter));
public static readonly RoutedEvent ModalContentHiddenEvent = EventManager.RegisterRoutedEvent("ModalContentHidden", RoutingStrategy.Bubble,
typeof(RoutedEventArgs), typeof(ModalContentPresenter));
public event RoutedEventHandler PreviewModalContentShown
{
add { AddHandler(PreviewModalContentShownEvent, value); }
remove { RemoveHandler(PreviewModalContentShownEvent, value); }
}
public event RoutedEventHandler ModalContentShown
{
add { AddHandler(ModalContentShownEvent, value); }
remove { RemoveHandler(ModalContentShownEvent, value); }
}
public event RoutedEventHandler PreviewModalContentHidden
{
add { AddHandler(PreviewModalContentHiddenEvent, value); }
remove { RemoveHandler(PreviewModalContentHiddenEvent, value); }
}
public event RoutedEventHandler ModalContentHidden
{
add { AddHandler(ModalContentHiddenEvent, value); }
remove { RemoveHandler(ModalContentHiddenEvent, value); }
}
#endregion
#region ModalContentPresenter implementation
static ModalContentPresenter()
{
traversalDirection = new TraversalRequest(FocusNavigationDirection.First);
}
public ModalContentPresenter()
{
layoutRoot = new ModalContentPresenterPanel();
primaryContentPresenter = new ContentPresenter();
modalContentPresenter = new ContentPresenter();
overlay = new Border();
AddVisualChild(layoutRoot);
logicalChildren = new object[2];
overlay.Background = OverlayBrush;
overlay.Child = modalContentPresenter;
overlay.Visibility = Visibility.Hidden;
layoutRoot.Children.Add(primaryContentPresenter);
layoutRoot.Children.Add(overlay);
}
public void ShowModalContent()
{
if (!IsModal)
IsModal = true;
}
public void HideModalContent()
{
if (IsModal)
IsModal = false;
}
private void RaiseModalContentShownEvents()
{
RoutedEventArgs args = new RoutedEventArgs(PreviewModalContentShownEvent);
OnPreviewModalContentShown(args);
if (!args.Handled)
{
args = new RoutedEventArgs(ModalContentShownEvent);
OnModalContentShown(args);
}
}
private void RaiseModalContentHiddenEvents()
{
RoutedEventArgs args = new RoutedEventArgs(PreviewModalContentHiddenEvent);
OnPreviewModalContentHidden(args);
if (!args.Handled)
{
args = new RoutedEventArgs(ModalContentHiddenEvent);
OnModalContentHidden(args);
}
}
protected virtual void OnPreviewModalContentShown(RoutedEventArgs e)
{
RaiseEvent(e);
}
protected virtual void OnModalContentShown(RoutedEventArgs e)
{
RaiseEvent(e);
}
protected virtual void OnPreviewModalContentHidden(RoutedEventArgs e)
{
RaiseEvent(e);
}
protected virtual void OnModalContentHidden(RoutedEventArgs e)
{
RaiseEvent(e);
}
#endregion
#region property changed callbacks
private static void OnIsModalChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
ModalContentPresenter control = (ModalContentPresenter)d;
if ((bool)e.NewValue == true)
{
control.cachedKeyboardNavigationMode = KeyboardNavigation.GetTabNavigation(control.primaryContentPresenter);
KeyboardNavigation.SetTabNavigation(control.primaryContentPresenter, KeyboardNavigationMode.None);
control.overlay.Visibility = Visibility.Visible;
control.overlay.MoveFocus(traversalDirection);
control.RaiseModalContentShownEvents();
}
else
{
control.overlay.Visibility = Visibility.Hidden;
KeyboardNavigation.SetTabNavigation(control.primaryContentPresenter, control.cachedKeyboardNavigationMode);
control.primaryContentPresenter.MoveFocus(traversalDirection);
control.RaiseModalContentHiddenEvents();
}
}
private static void OnContentChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
ModalContentPresenter control = (ModalContentPresenter)d;
if (e.OldValue != null)
control.RemoveLogicalChild(e.OldValue);
control.primaryContentPresenter.Content = e.NewValue;
control.AddLogicalChild(e.NewValue);
control.logicalChildren[0] = e.NewValue;
}
private static void OnModalContentChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
ModalContentPresenter control = (ModalContentPresenter)d;
if (e.OldValue != null)
control.RemoveLogicalChild(e.OldValue);
control.modalContentPresenter.Content = e.NewValue;
control.AddLogicalChild(e.NewValue);
control.logicalChildren[1] = e.NewValue;
}
private static void OnOverlayBrushChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
ModalContentPresenter control = (ModalContentPresenter)d;
control.overlay.Background = (Brush)e.NewValue;
}
#endregion
#region FrameworkElement overrides
protected override Visual GetVisualChild(int index)
{
if (index < 0 || index > 1)
throw new ArgumentOutOfRangeException("index");
return layoutRoot;
}
protected override int VisualChildrenCount
{
get { return 1; }
}
protected override IEnumerator LogicalChildren
{
get { return logicalChildren.GetEnumerator(); }
}
protected override Size ArrangeOverride(Size finalSize)
{
layoutRoot.Arrange(new Rect(finalSize));
return finalSize;
}
protected override Size MeasureOverride(Size availableSize)
{
layoutRoot.Measure(availableSize);
return layoutRoot.DesiredSize;
}
#endregion
#region layout panel
class ModalContentPresenterPanel : Panel
{
protected override Size MeasureOverride(Size availableSize)
{
Size resultSize = new Size(0, 0);
foreach (UIElement child in Children)
{
child.Measure(availableSize);
resultSize.Width = Math.Max(resultSize.Width, child.DesiredSize.Width);
resultSize.Height = Math.Max(resultSize.Height, child.DesiredSize.Height);
}
return resultSize;
}
protected override Size ArrangeOverride(Size finalSize)
{
foreach (UIElement child in InternalChildren)
{
child.Arrange(new Rect(finalSize));
}
return finalSize;
}
}
#endregion
}
}
您不应该这样做（至少，这绝对不是MVVM方式）。使用IsModal属性和数据绑定：
<Controls:ModalContentPresenter x:Name="modalContent" IsModal="{Binding IsModal}">
其中绑定表达式中的IsModal是视图模型中的绑定数据属性。
在MVVM中，任何来回的数据都应通过视图模型上的数据绑定属性来完成。这实际上包括ContentPresenter的所有属性-只需添加绑定即可。但是，如果要以对MVVM友好的方式调用XAML对象的方法，则可以使用Action。
假设我想通过视图模型将焦点设置在文本框上（人为的例子，我知道还有其他的MVVM方法可以做到这一点-只需要一个需要视图的子对象的例子）。
首先，在XAML中为应该获得焦点的文本框指定一个名称，即，
<TextBox x:Name="textBox1"/>
在您的视图模型上，为操作添加属性：
public Action FocusAction {get;set;}
在加载视图之前或加载视图时，获取DataContext（即视图模型），然后将Action添加到后面的代码（视图的.cs文件）：
ViewModel vm = (ViewModel)this.DataContext;
if ( vm.FocusAction == null )
vm.FocusAction= new Action(() => this.textBox1.Focus());
例如，您可以实现IsLoaded事件并在那里进行。您也可以在InitializeComponent之后的构造函数中执行此操作，只要它创建了视图模型实例或将其作为参数传入即可。关键在于视图模型已经实例化并分配给视图的数据上下文。
然后在您的视图模型中，无论您想向该文本框添加焦点的位置，都致电：
FocusAction();
由于我上面刚刚显示的内容要求您的视图将DataContext投射到特定的视图模型，所以我要做的是为我需要的各种操作创建一个接口，如下所示：
interface IFocusable
{
Action FocusAction {get;set;}
}
然后，我使我的视图模型实现该接口。完成此操作后，在我看来，我的代码可以隐藏为：
if(this.DataContext is IFocusable)
((IFocusable)this.DataContext).FocusAction = new Action(() => this.textBox1.Focus());
[我认为这使它更加符合MVVM，因为它没有紧密地耦合到特定的视图模型，因此只要视图模型是可以使用它的视图模型类型，视图就知道它可以添加操作。
更多详细信息和此处提供的另一个示例：http://jkshay.com/closing-a-wpf-window-using-mvvm-and-minimal-代码隐藏/
我知道已经好几年了，但是我也面临着同样的情况，所以这是我的回答，以防有人发现它有用...在您的xaml文件中，请在DataContext中引用ViewModel类：
<Window.DataContext>
<local:YourViewModel x:Name="yourViewModel"/>
</Window.DataContext>
在您的ViewModel类中，以您的xaml文件作为参数并创建一个私有成员来保存一个公共函数：
private MainWindow mainWindow;
public void OnViewInitialized(MainWindow mainWindow)
{
this.mainWindow = mainWindow;
}
在您后面的代码中，使用该函数传递您在xaml中定义的'yourViewModel'：
public MainWindow()
{
InitializeComponent();
marsSiteMapViewModel.OnViewInitialized(this);
}
就这样:)现在，您可以使用mainWindow成员从ViewModel访问所有xaml元素，只需为其命名即可。
mainWindow.textBox1