小贝子编程

用户控件中的自定义依赖项属性不绑定



我有一个图像屏幕用户控件，它包含一个WPF图像控件和一些输入控件，它显示经过一些用户控制的数据处理后的图像数据。我使用的是MVVM设计模式，因此它由一个视图和一个视图模型组成——控件是一个库的一部分，该库旨在从多个项目中使用，因此该模型将特定于消费项目。ImageScreen如下所示：

ImageScreenView XAML：

<UserControl (...)
xmlns:local="clr-namespace:MyCompany.WPFUserControls" x:Class="MyCompany.WPFUserControls.ImageScreenView"
(...) >
<UserControl.DataContext>
<local:ImageScreenViewModel/>
</UserControl.DataContext>
<Border>
(...)    // control layout, should not be relevant to the problem
</Border>
</UserControl>

ViewModel是我实现的INotifyPropertyChanged接口的子类：

NotifyPropertyChanged.cs:

using System.Collections.Generic;
using System.ComponentModel;
using System.Runtime.CompilerServices;
namespace MyCompany
{
public abstract class NotifyPropertyChanged : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private readonly Dictionary<string, PropertyChangedEventArgs> argumentsCache = new Dictionary<string, PropertyChangedEventArgs>();
protected bool SetProperty<T>(ref T field, T newValue, [CallerMemberName]string propertyName = null)
{
if (!EqualityComparer<T>.Default.Equals(field, newValue))
{
field = newValue;
if (argumentsCache != null)
{
if (!argumentsCache.ContainsKey(propertyName))
argumentsCache[propertyName] = new PropertyChangedEventArgs(propertyName);
PropertyChanged?.Invoke(this, argumentsCache[propertyName]);
return true;
}
else
return false;
}
else
return false;
}
}
}

视图模型本身主要由视图能够绑定到的一组属性组成，如下所示：

ImageScreenViewModel.cs:

using System;
using System.ComponentModel;
using System.Windows.Media.Imaging;
namespace MyCompany.WPFUserControls
{
public class ImageScreenViewModel : NotifyPropertyChanged
{
public ushort[,] ImageData
{
get => imageData;
set => SetProperty(ref imageData, value);
}
(...)
private ushort[,] imageData;
(...)
public ImageScreenViewModel()
{
PropertyChanged += OnPropertyChanged;
}
protected void OnPropertyChanged(object sender, PropertyChangedEventArgs eventArgs)
{
switch (eventArgs.PropertyName)
{
(...) // additional property changed event logic
}
}
(...)
}
}

在特定项目中，此控件是主窗口View的一部分，而主窗口View又有自己的ViewModel。由于ImageScreen应该根据自己视图中的选择来处理和显示数据，因此它只应该暴露一个属性，即图像数据(这是一个2D ushort数组btw(，其余的应由其视图模型处理。然而，使用控件的主窗口ViewModel对ImageScreen ViewModel没有直接的了解，所以我不能简单地访问它并直接传递数据。因此，我已经将ImageData定义为ImageScreen代码隐藏中的依赖属性(我尽可能避免代码隐藏，但我认为我不能仅在XAML中定义依赖属性(，并使用PropertyChanged回调将数据转发到ViewModel。然后，ImageData依赖项属性将通过MainWindowView中的XAML数据绑定绑定到MainWindowViewModel。所以后面的ImageScreenView代码看起来是这样的：

ImageScreenView.cs:

using System.Windows;
using System.Windows.Controls;
namespace MyCompany.WPFUserControls
{
public partial class ImageScreenView : UserControl
{
public ushort[,] ImageData
{
get => (ushort[,])GetValue(ImageDataProperty);
set => SetValue(ImageDataProperty, value);
}
public static readonly DependencyProperty ImageDataProperty = DependencyProperty.Register("ImageData", typeof(ushort[,]), typeof(ImageScreenV),
new PropertyMetadata(new PropertyChangedCallback(OnImageDataChanged)));
public ImageScreenView()
{
InitializeComponent();
}
private static void OnImageDataChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs eventArgs)
{
ImageScreenViewModel imageScreenViewModel = (dependencyObject as ImageScreenView).DataContext as ImageScreenViewModel;
if (imageScreenViewModel != null)
imageScreenViewModel.ImageData = (ushort[,])eventArgs.NewValue;
}
}
}

主窗口XAML如下所示：

主窗口视图XAML：

<Window (...)
xmlns:local="clr-namespace:MyCompany.MyProject" x:Class="MyCompany.MyProject.MainWindowView"
xmlns:uc="clr-namespace:MyCompany.WPFUserControls;assembly=WPFUserControls"
(...) >
<Window.DataContext>
<local:MainWindowViewModel/>
</Window.DataContext>
<Grid Width="Auto" Height="Auto">
<uc:ImageScreenView (...) ImageData="{Binding LiveFrame}"/>
(...)
<uc:ImageScreenView (...) ImageData="{Binding SavedFrame}"/>
(...)
</Grid>
</Window>

然后在主窗口ViewModel中，绑定的属性LiveFrame和SavedFrame应更新为其适当的值。ViewModel的相关部分如下所示：

MainWindowViewModel.cs:

using System;
using System.ComponentModel;
using System.Threading.Tasks;
using System.Windows.Input;
namespace MyCompany.MyProject
{
public class MainWindowViewModel : NotifyPropertyChanged
{
(...)
public ushort[,] LiveFrame
{
get => liveFrame;
set => SetProperty(ref liveFrame, value);
}
public ushort[,] ResultFrame
{
get => resultFrame;
set => SetProperty(ref resultFrame, value);
}
(...)
private ushort[,] liveFrame;
private ushort[,] resultFrame;
(...)
public MainWindowViewModel()
{
PropertyChanged += OnPropertyChanged;
InitCamera();
}
#region methods
protected void OnPropertyChanged(object sender, PropertyChangedEventArgs eventArgs)
{
switch (eventArgs.PropertyName)
{
(...) // additional property changed event logic
}
}
private bool InitCamera()
{
(...) // camera device initialization, turn streaming on
}
(...)
private void OnNewFrame(ushort[,] thermalImg, ushort width, ushort height, ...)
{
LiveFrame = thermalImg;  // arrival of new frame data
}
private void Stream()
{
while (streaming)
{
(...) // query new frame data
}
}
(...)
}
}

每当新的帧数据到达时，MainWindowViewModel的LiveFrame属性就会更新。我不质疑相机代码，因为我在其他地方使用了它，没有问题，在调试模式下，我可以看到数据正确到达。但是，由于某些原因，当设置LiveFrame属性时，即使它绑定到LiveFrame属性，它也不会触发ImageScreen的ImageData依赖属性的更新。我在依赖属性的setter和PropertyChanged回调中设置了断点，但它们没有被执行。尽管我已经在MainWindowView XAML中显式设置了绑定，而且我用于ViewModels属性更改的NotifyPropertyChanged基类应该(实际上在其他任何地方(引发刷新数据绑定的PropertyChanged事件，但绑定似乎并不存在。我尝试将绑定设置为双向，并将UpdateSourceTrigger设置为OnPropertyChanged，但都没有效果。最让我困惑的是，MainWindowView中的其他数据绑定到其ViewModel中的属性都很好，其中一个绑定还带有我自己定义的自定义依赖项属性，尽管在这种情况下，它是一个自定义控件，而不是用户控件。

有人知道我把数据绑定搞砸了吗？

编辑：应Ed的要求，我将重新发布完整的ImageScreenView.xaml和ImageScreenView Model.cs:

ImageScreenV.xaml:

<UserControl xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
xmlns:local="clr-namespace:MyCompany.WPFUserControls" x:Class="MyCompany.WPFUserControls.ImageScreenV"
xmlns:cc="clr-namespace:MyCompany.WPFCustomControls;assembly=WPFCustomControls"
mc:Ignorable="d" d:DesignWidth="401" d:DesignHeight="300">
<Border BorderBrush="{Binding BorderBrush, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:ImageScreenV}}}"
Background="{Binding Background, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:ImageScreenV}}}"
BorderThickness="{Binding BorderThickness, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:ImageScreenV}}}">
<Border.DataContext>
<local:ImageScreenVM x:Name="viewModel"/>
</Border.DataContext>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition MinWidth="{Binding ImageWidth}"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition MinHeight="{Binding ImageHeight}"/>
</Grid.RowDefinitions>
<Image MinWidth="{Binding ImageWidth}" MinHeight="{Binding ImageHeight}"
Source="{Binding ScreenImageSource}"/>
<StackPanel Grid.Column="1" Margin="3">
<Label Content="Scaling Method"/>
<ComboBox MinWidth="95" SelectedIndex="{Binding ScalingMethodIndex}">
<ComboBoxItem Content="Manual"/>
<ComboBoxItem Content="MinMax"/>
<ComboBoxItem Content="Sigma 1"/>
<ComboBoxItem Content="Sigma 3"/>
</ComboBox>
<Label Content="Minimum" Margin="0,5,0,0"/>
<cc:DoubleSpinBox DecimalPlaces="2" Prefix="T = " Suffix=" °C" Maximum="65535" Minimum="0" MinHeight="22"
Value="{Binding ScalingMinimum, Mode=TwoWay}"  VerticalContentAlignment="Center"
IsEnabled="{Binding ScalingManually}"/>
<Label Content="Maximum"/>
<cc:DoubleSpinBox DecimalPlaces="2" Prefix="T = " Suffix=" °C" Maximum="65535" Minimum="0" MinHeight="22"
Value="{Binding ScalingMaximum, Mode=TwoWay}"  VerticalContentAlignment="Center"
IsEnabled="{Binding ScalingManually}"/>
<Label Content="Color Palette" Margin="0,5,0,0"/>
<ComboBox MinWidth="95" SelectedIndex="{Binding ColorPaletteIndex}">
<ComboBoxItem Content="Alarm Blue"/>
<ComboBoxItem Content="Alarm Blue Hi"/>
<ComboBoxItem Content="Alarm Green"/>
<ComboBoxItem Content="Alarm Red"/>
<ComboBoxItem Content="Fire"/>
<ComboBoxItem Content="Gray BW"/>
<ComboBoxItem Content="Gray WB"/>
<ComboBoxItem Content="Ice32"/>
<ComboBoxItem Content="Iron"/>
<ComboBoxItem Content="Iron Hi"/>
<ComboBoxItem Content="Medical 10"/>
<ComboBoxItem Content="Rainbow"/>
<ComboBoxItem Content="Rainbow Hi"/>
<ComboBoxItem Content="Temperature"/>
</ComboBox>
</StackPanel>
</Grid>
</Border>
</UserControl>

ImageScreenVM.cs:

using MyCompany.Vision;
using System;
using System.ComponentModel;
using System.Windows.Media.Imaging;
namespace MyCompany.WPFUserControls
{
public class ImageScreenVM : NotifyPropertyChanged
{
#region properties
public BitmapSource ScreenImageSource
{
get => screenImageSource;
set => SetProperty(ref screenImageSource, value);
}
public int ScalingMethodIndex
{
get => scalingMethodIndex;
set => SetProperty(ref scalingMethodIndex, value);
}
public int ColorPaletteIndex
{
get => colorPaletteIndex;
set => SetProperty(ref colorPaletteIndex, value);
}
public double ScalingMinimum
{
get => scalingMinimum;
set => SetProperty(ref scalingMinimum, value);
}
public double ScalingMaximum
{
get => scalingMaximum;
set => SetProperty(ref scalingMaximum, value);
}
public bool ScalingManually
{
get => scalingManually;
set => SetProperty(ref scalingManually, value);
}
public uint ImageWidth
{
get => imageWidth;
set => SetProperty(ref imageWidth, value);
}
public uint ImageHeight
{
get => imageHeight;
set => SetProperty(ref imageHeight, value);
}
public MyCompany.Vision.Resolution Resolution
{
get => resolution;
set => SetProperty(ref resolution, value);
}
public ushort[,] ImageData
{
get => imageData;
set => SetProperty(ref imageData, value);
}
public Action<ushort[,], byte[,], (double, double), MyCompany.Vision.Processing.Scaling> ScalingAction
{
get => scalingAction;
set => SetProperty(ref scalingAction, value);
}
public Action<byte[,], byte[], MyCompany.Vision.Processing.ColorPalette> ColoringAction
{
get => coloringAction;
set => SetProperty(ref coloringAction, value);
}
#endregion
#region fields
private BitmapSource screenImageSource;
private int scalingMethodIndex;
private int colorPaletteIndex;
private double scalingMinimum;
private double scalingMaximum;
private bool scalingManually;
private uint imageWidth;
private uint imageHeight;
private MyCompany.Vision.Resolution resolution;
private ushort[,] imageData;
private byte[,] scaledImage;
private byte[] coloredImage;
private Action<ushort[,], byte[,], (double, double), MyCompany.Vision.Processing.Scaling> scalingAction;
private Action<byte[,], byte[], MyCompany.Vision.Processing.ColorPalette> coloringAction;
#endregion
public ImageScreenVM()
{
PropertyChanged += OnPropertyChanged;
}
#region methods
protected void OnPropertyChanged(object sender, PropertyChangedEventArgs eventArgs)
{
switch (eventArgs.PropertyName)
{
case nameof(ImageData):
if (imageData.GetLength(0) != resolution.Height || imageData.GetLength(1) != resolution.Width)
Resolution = new MyCompany.Vision.Resolution(checked((uint)imageData.GetLength(1)), checked((uint)imageData.GetLength(0)));
goto case nameof(ScalingMaximum);
case nameof(ScalingMethodIndex):
ScalingManually = scalingMethodIndex == (int)MyCompany.Vision.Processing.Scaling.Manual;
goto case nameof(ScalingMaximum);
case nameof(ColorPaletteIndex):
case nameof(ScalingMinimum):
case nameof(ScalingMaximum):
ProcessImage();
break;
case nameof(Resolution):
scaledImage = new byte[resolution.Height, resolution.Width];
coloredImage = new byte[resolution.Pixels() * 3];
ImageWidth = resolution.Width;
ImageHeight = resolution.Height;
break;
}
}
private void ProcessImage()
{
// not sure yet if I stick to this approach
if (scalingAction != null && coloringAction != null)
{
scalingAction(imageData, scaledImage, (scalingMinimum, scalingMaximum), (Processing.Scaling)scalingMethodIndex);
coloringAction(scaledImage, coloredImage, (Processing.ColorPalette)colorPaletteIndex);
}
}
#endregion
}
}

这会断开与MainWindowViewModel的LiveFrame和SavedFrame属性的绑定，因为它将DataContext设置为不具有以下属性的ImageScreenViewModel：

<UserControl.DataContext>
<local:ImageScreenViewModel/>
</UserControl.DataContext>

我不知道ImageScreenViewModel的用途，但您可能应该将其替换为UserControl类本身的依赖属性，并使用RelativeSource:在UserControl的XAML标记中绑定到这些属性

{Binding UcProperty, RelativeSource={RelativeSource AncestorType=UserControl}}

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