我有一个MainWindow.xaml,MainwindowViewModel.cs,HaemogramReport.xaml和HaemogramReport.xaml.cs。我的项目中也有其他文件,但问题在于上述四个文件。 我在这里发布最小代码,以便其他人可以发现问题。在WPF绑定不按预期工作
现在HaemogramReport.xaml我宣布一些控件像Grid
,TextBox
,TextBlock
,Rectangle
,Border
,ContentControl
等
例如HaemogramReport.xaml
样子:
<Page.DataContext>
<vm:MainWindowViewModel />
</Page.DataContext>
<Grid DataContext="{Binding Source={StaticResource Settings}}" PreviewMouseDown="Object_Selection" x:Name="Root">
<Border Style="{StaticResource BorderStyle}" x:Name="HaemogramTestBorder"
Grid.Row="{Binding Default.HaemogramTestGridRow}" Grid.Column="{Binding Default.HaemogramTestGridColumn}"
Grid.RowSpan="{Binding Default.HaemogramTestGridRowSpan}" Grid.ColumnSpan="{Binding Default.HaemogramTestGridColumnSpan}">
<Grid>
<Rectangle Fill="Transparent" x:Name="HaemogramTestRectangle"/>
<TextBlock x:Name="HaemogramTestTextBlock"
Text="{Binding Default.HaemogramTestText}" Visibility="{Binding Default.HaemogramTestVisibility}"
Background="{Binding Default.HaemogramTestBackground, Converter={StaticResource colorToSolidColorBrushConverter}}"
Foreground="{Binding Default.HaemogramTestForeground, Converter={StaticResource colorToSolidColorBrushConverter}}"
FontFamily="{Binding Default.HaemogramTestFontFamily, Converter={StaticResource stringToFontFamilyConverter}}"
FontSize="{Binding Default.HaemogramTestFontSize}"
FontWeight="{Binding Default.HaemogramTestFontWeight}" FontStyle="{Binding Default.HaemogramTestFontStyle}"
HorizontalAlignment="{Binding Default.HaemogramTestHorizontalAlignment}"
VerticalAlignment="{Binding Default.HaemogramTestVerticalAlignment}"
Margin="{Binding Default.HaemogramTestMargin}" />
</Grid>
</Border>
</Grid>
当我点击任何的上述声明元素中的元素将引发名为Root
的网格的mousedown事件。
该事件处理程序在HaemogramReport.xmal.cs
中。那就是:
private void Object_Selection(object sender, MouseButtonEventArgs e)
{
var mouseWasDownOn = e.Source as FrameworkElement;
if (mouseWasDownOn != null)
{
foreach (Border border in FindVisualChildren<Border>(Root))
{
border.BorderBrush = Brushes.Transparent;
}
if (!(mouseWasDownOn is Border))
{
FindParent<Border>(mouseWasDownOn).BorderBrush = Brushes.Orange;
}
MainWindowViewModel mwvm = new MainWindowViewModel();
mwvm.SelectedObj = mouseWasDownOn;
}
}
public static IEnumerable<T> FindVisualChildren<T>(DependencyObject depObj) where T : DependencyObject
{
if (depObj != null)
{
for (int i = 0; i < VisualTreeHelper.GetChildrenCount(depObj); i++)
{
DependencyObject child = VisualTreeHelper.GetChild(depObj, i);
if (child != null && child is T)
{
yield return (T)child;
}
foreach (T childOfChild in FindVisualChildren<T>(child))
{
yield return childOfChild;
}
}
}
}
public static T FindParent<T>(DependencyObject child) where T : DependencyObject
{
//get parent item
DependencyObject parentObject = VisualTreeHelper.GetParent(child);
//we've reached the end of the tree
if (parentObject == null) return null;
//check if the parent matches the type we're looking for
T parent = parentObject as T;
if (parent != null)
return parent;
else
return FindParent<T>(parentObject);
}
在鼠标按下电网的处理器命名Root
,我说mwvm.SelectedObj = mouseWasDownOn;
SelectedObj是在MainwindowViewModel.cs
声明类型FrameworkElement的的属性如下:
private FrameworkElement selectedObj;
public FrameworkElement SelectedObj
{
get
{
return selectedObj;
}
set
{
selectedObj = value;
OnPropertyChanged("SelectedObj");
}
}
现在我的主窗口我有例如一个网格和一个文本框在里面。有问题的绑定在这里声明。 XAML的样子:
<Window.DataContext>
<vm:MainWindowViewModel />
</Window.DataContext>
<Grid DataContext="{Binding SelectedObj, UpdateSourceTrigger=PropertyChanged}">
<TextBox Text="{Binding Text, UpdateSourceTrigger=PropertyChanged, TargetNullValue='null', FallbackValue='Error'}"/>
</Grid>
当使用上面的代码,我总是在上面的文本框中的文本Error
。
当时我认为这可能是绑定错误的第一次机会,让我改变了我的MainWindowViewModel.cs
如下:
public class MainWindowViewModel : INotifyPropertyChanged
{
public MainWindowViewModel()
{
SelectedObj = txt;
}
TextBlock txt = new TextBlock()
{
Text = "123"
};
private FrameworkElement selectedObj;
public FrameworkElement SelectedObj
{
get
{
return selectedObj;
}
set
{
selectedObj = value;
OnPropertyChanged("SelectedObj");
}
}
}
作出上述改变后,当我跑我的项目,我可以在文本框中看到123
但当我点击任何元素时,文本框中的文本不会改变。
现在这里的问题是,如果它的绑定错误,那么为什么在第二个例子中,我在文本框中获得123
,而在第一个示例中,我获得Error
- 回退值。
如果它不是一个绑定错误,那么上述代码中的问题是什么?
更新
当我调试,我发现SelectedObj
get
一部分不会被调用。但我不知道为什么?
更新 - 里德科普塞
这是我的新类:
public class DesignMethods
{
public static void FindCurrentlyClickedElement(DependencyObject Root, MouseButtonEventArgs e, MainWindowViewModel vm)
{
var mouseWasDownOn = e.OriginalSource as FrameworkElement;
if (mouseWasDownOn != null)
{
foreach (Border border in FindVisualChildren<Border>(Root))
{
border.BorderBrush = Brushes.Transparent;
}
if (!(mouseWasDownOn is Border))
{
FindParent<Border>(mouseWasDownOn).BorderBrush = Brushes.Orange;
}
vm.SelectedObj = mouseWasDownOn;
}
}
public static IEnumerable<T> FindVisualChildren<T>(DependencyObject depObj) where T : DependencyObject
{
if (depObj != null)
{
for (int i = 0; i < VisualTreeHelper.GetChildrenCount(depObj); i++)
{
DependencyObject child = VisualTreeHelper.GetChild(depObj, i);
if (child != null && child is T)
{
yield return (T)child;
}
foreach (T childOfChild in FindVisualChildren<T>(child))
{
yield return childOfChild;
}
}
}
}
public static T FindParent<T>(DependencyObject child) where T : DependencyObject
{
//get parent item
DependencyObject parentObject = VisualTreeHelper.GetParent(child);
//we've reached the end of the tree
if (parentObject == null) return null;
//check if the parent matches the type we're looking for
T parent = parentObject as T;
if (parent != null)
return parent;
else
return FindParent<T>(parentObject);
}
}
我用它喜欢:
private void Object_Selection(object sender, MouseButtonEventArgs e)
{
DesignMethods.FindCurrentlyClickedElement(Root, e, this.DataContext as MainWindowViewModel);
}
2天前我问了这个问题。现在我已经在一个新类中移动了Object_Selection,这样我就可以在很多地方使用它了。此外,我已将此方法标记为“静态”。我不能使用'this'。所以我想我应该通过'MainWindowViewModel'的Current Instance,并且我已经这样做了。但是我仍然没有对输出做任何改变。 – Khushi
有关更多详细信息,请参阅更新后的问题。另外我在xaml中声明了我的datacontext。这会影响你提到的代码吗? – Khushi
@Khushi您确定要更改虚拟机的正确实例吗?如果你在setter中放置一个断点,你会看到这个变化吗? –