[英]C# WPF Listview item refresh not firing after OnPropertyChanged
我創建了一個視圖控件以圖形方式顯示數據。 由於可能有許多視圖實例,因此我使用了ListView控件,並將其綁定到可觀察到的對象集合-圖紙。 Sheets是SheetContainer對象的一個可觀察的集合,該對象具有工作表和名稱。 查看器顯示工作表。
列表視圖的xaml看起來像:
<ListView x:Name="ListViewSheetSlider" Height="170" Grid.Row="1" BorderThickness="0"
ItemsSource="{Binding Sheets}" SelectionChanged="ListViewSheetSlider_SelectionChanged" >
<ListView.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Vertical">
<TextBlock Text="{Binding Name}" />
<Viewbox Width="150" Height="150">
<SheetViewer:Viewer SetSheet="{Binding MySheet, NotifyOnSourceUpdated=True}" />
</Viewbox>
</StackPanel>
</DataTemplate>
</ListView.ItemTemplate>
<ListView.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="Horizontal"></StackPanel>
</ItemsPanelTemplate>
</ListView.ItemsPanel>
</ListView>
SelectionChanged方法如下所示:
private void UpdateSheetAndSlider()
{
workspace.Sheets[SelectedSheetIndex] = MySheetDesigner.Sheet;
// ((SheetContainer)ListViewSheetSlider.SelectedItem).MySheet = MySheetDesigner.Sheet;
Sheets[SelectedSheetIndex].MySheet = MySheetDesigner.Sheet;
}
private void MySheetDesigner_SheetChanged(object sender, EventArgs e)
{
UpdateSheetAndSlider();
}
private void ListViewSheetSlider_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
int index = ListViewSheetSlider.SelectedIndex;
UpdateSheetAndSlider();
SelectedSheetIndex = index;
MySheetDesigner.Sheet = workspace.Sheets[index];
ListViewSheetSlider.UpdateLayout();
}
SheetContainer實現很簡單。 看起來像:
public class SheetContainer : INotifyPropertyChanged
{
public string Name { get; set; }
private Sheet mySheet;
public Sheet MySheet
{
get => mySheet;
set
{
mySheet = value;
OnPropertyChanged("MySheet");
}
}
#region INotifyPropertyChanged Handler
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
#endregion
}
查看器xaml和代碼隱藏如下所示:
<UserControl x:Class="SheetViewer.Viewer"
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:SheetViewer"
xmlns:cad="clr-namespace:Cad;assembly=Cad"
mc:Ignorable="d"
d:DesignHeight="450" d:DesignWidth="800">
<Grid>
<cad:Cad
x:Name="CadSurface" >
</cad:Cad>
</Grid>
</UserControl>
后面的代碼:
public partial class Viewer : UserControl
{
public static readonly DependencyProperty SetSheetProperty =
DependencyProperty.Register("SetSheet", typeof(Sheet), typeof(Viewer), new
PropertyMetadata(default(Sheet), new PropertyChangedCallback(OnSetSheetChanged)));
public Sheet SetSheet
{
get { return (Sheet)GetValue(SetSheetProperty); }
set { SetValue(SetSheetProperty, value);}
}
private static void OnSetSheetChanged(DependencyObject d,
DependencyPropertyChangedEventArgs e)
{
Viewer UserControl1Control = d as Viewer;
UserControl1Control.OnSetSheetChanged(e);
}
private void OnSetSheetChanged(DependencyPropertyChangedEventArgs e)
{
//tbTest.Text = e.NewValue.ToString();
Sheet s = (Sheet)e.NewValue;
DrawSheet(s);
}
public Viewer()
{
InitializeComponent();
}
private void DrawSheet(Sheet sheet)
{
CadSurface.Draw();
}
}
我希望在列表視圖中的選擇更改時能夠觸發DrawSheet方法。 更改的屬性的確在SheetContainer中觸發,但不會進一步傳播以繪制圖紙。 請注意,在填充列表視圖時,將正確調用方法並繪制初始視圖。
我已經花費了大量時間,但是不知何故缺少了關鍵要素。 誰能幫忙嗎?
謝謝
如果分配給SetSheet的實例相同,則不會觸發DependencyPropertyChanged事件。 這將解釋一切。 關鍵是DependencyProperty在設置值之前檢查新舊值是否相等。 如果它們相等,則不會傳播任何更改。
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