[英]Update ItemsControl when an item in an ObservableCollection is updated
[英]ItemsControl view doesn't updated when an item in ObservableCollection is updated
簡介 :
嗨,我在這里遇到一個奇怪的問題。 如果我要更新模型(例如,更改IsSelected
的值),則我的ItemsControl
不會更新視圖。
但是, IsSelected
用途之一是,如果該值為true
,則MusicalNotationBox
的背景(UserControl)更改為藍色,如果為false
則將其更改為透明。
很多人問: 為什么不使用觸發器,例如
Focus
forIsSelected
? 因為它不僅用於“視覺”目的。 我有一個命令,可以更改VM的MusicalNotations
中每個MusicalNotation
對象的某些Property
(例如Note的Octave),該IsSelected==true
(支持IsSelected==true
),所以我認為我需要在模型中使用IsSelected
。 但這不是這里的問題,因此請不要僅就此問題回答。
問題是 :
<c:MusicalNotationBox DataContext={Binding}/>
(ofc及其在VM中的朋友,也稱為正確屬性),則它會完美同步 。 因此,我不太確定問題出在OC上。 MusicalNotation
添加到列表中,那么視圖也會更新。 我已經閱讀了“ Observable Collection不會更新ItemsControl`,但仍然找不到令人滿意的答案”(在Google和此處)的幾個主題。
這是我的代碼(為了清楚起見,代碼可能會被修剪(...)):
模型
public class MusicalNotation : ... INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
...
private bool _isSelected;
...
public bool IsSelected
{
get { return _isSelected; }
set { _isSelected = value; NotifyPropertyChanged("IsSelected"); }
}
...
public MusicalNotation()
{
...
IsSelected = false;
}
...
private void NotifyPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
查看模型
public class MainWindowModelView : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private ObservableCollection<MusicalNotation> _musicalNotations;
...
public ObservableCollection<MusicalNotation> MusicalNotations
{
get { return _musicalNotations; }
set { _musicalNotations = value; NotifyPropertyChanged("MusicalNotations"); }
}
public MainWindowModelView()
{
...
MusicalNotations = new ObservableCollection<MusicalNotation>();
//Direct initialization for testing purpose
MusicalNotations.Add(MusicalNotation.GetEmptyNote(new TimeSignature(4, 4)));
MusicalNotations.Add(MusicalNotation.GetEmptyNote(new TimeSignature(4, 4)));
foreach (MusicalNotation item in MusicalNotations)
{
item.IsSelected = true;
}
}
private void NotifyPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
視圖
<Window ...>
<Window.Resources>
</Window.Resources>
<Window.InputBindings>
...
</Window.InputBindings>
<Grid>
...
<ItemsControl Grid.Column="0" Grid.Row="0" ItemsSource="{Binding MusicalNotations, Mode=OneWay}"
HorizontalAlignment="Center" VerticalAlignment="Center">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel IsItemsHost="True" Orientation="Horizontal"/>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<c:MusicalNotationBox/>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</Grid>
謝謝。
更新,我的MusicalNotationBox XAML
<UserControl x:Class="NumberedMusicScoresUserControl.MusicalNotationBox"
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:NumberedMusicScoresUserControl.MusicalNotationBoxProperties"
mc:Ignorable="d">
<UserControl.Resources>
<local:DotConverter x:Key="DotConverter"/>
<local:NoteConverter x:Key="NoteConverter"/>
<local:AccidentalConverter x:Key="AccidentalConverter"/>
<local:IsSelectedConverter x:Key="IsSelectedConverter"/>
</UserControl.Resources>
<Grid x:Name="grid" Margin="10,5,10,5"
HorizontalAlignment="Center" VerticalAlignment="Center"
Background="{Binding Path=MusicalNotation.IsSelected, Converter={StaticResource IsSelectedConverter}, Mode=OneWay}">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<TextBlock Grid.Column="0" Grid.Row="1"
Text="b"
Visibility="{Binding Path=MusicalNotation.Accidental, Converter={StaticResource AccidentalConverter}, ConverterParameter=FL, Mode=OneWay}"
FontSize="15" FontFamily="CourierNew"
HorizontalAlignment="Center" VerticalAlignment="Center"/>
<Path Grid.Column="1" Grid.Row="1" Stroke="Black" StrokeThickness="1" Stretch="Fill"
Visibility="{Binding Path=MusicalNotation.Accidental, Converter={StaticResource AccidentalConverter}, ConverterParameter=SP, Mode=OneWay}" >
<Path.Data>
<LineGeometry StartPoint="1,0" EndPoint="0,1">
<LineGeometry.Transform>
<RotateTransform CenterX="0" CenterY="0" Angle="30"/>
</LineGeometry.Transform>
</LineGeometry>
</Path.Data>
</Path>
<TextBlock Grid.Column="1" Grid.Row="1"
Text="{Binding Path=MusicalNotation.Note, Converter={StaticResource NoteConverter}, Mode=OneWay}"
FontSize="15" FontFamily="CourierNew"
HorizontalAlignment="Center" VerticalAlignment="Center"
Margin="2.5,0,2.5,0"/>
<ItemsControl Grid.Column="1" Grid.Row="0"
ItemsSource="{Binding Path=MusicalNotation.Octave, Converter={StaticResource DotConverter}, ConverterParameter=TOP, Mode=OneWay}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel IsItemsHost="True"/>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Ellipse HorizontalAlignment="Center" VerticalAlignment="Top"
Margin="{Binding Margin}" Fill="{Binding Fill}"
Width="{Binding Diameter}" Height="{Binding Diameter}"/>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
<ItemsControl Grid.Column="1" Grid.Row="2"
ItemsSource="{Binding Path=MusicalNotation.Octave, Converter={StaticResource DotConverter}, ConverterParameter=BOT, Mode=OneWay}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel IsItemsHost="True"/>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Ellipse HorizontalAlignment="Center" VerticalAlignment="Bottom"
Margin="{Binding Margin}" Fill="{Binding Fill}"
Width="{Binding Diameter}" Height="{Binding Diameter}"/>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
<ItemsControl Grid.Column="2" Grid.Row="1"
ItemsSource="{Binding Path=MusicalNotation.Dot, Converter={StaticResource DotConverter}, ConverterParameter=RIGHT, Mode=OneWay}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="Horizontal" IsItemsHost="True"/>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Ellipse HorizontalAlignment="Left" VerticalAlignment="Center"
Margin="{Binding Margin}" Fill="{Binding Fill}"
Width="{Binding Diameter}" Height="{Binding Diameter}"/>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</Grid>
(我不包括它,因為我認為,如果“單數”正確,那么我的UserControl也正確。不過,可能是錯誤的。)
用戶控件的DataContext
是MusicalNotation
對象,因此在綁定而不是使用
Background="{Binding Path=MusicalNotation.IsSelected, Converter={StaticResource ....
只是使用
Background="{Binding Path=IsSelected, Converter={StaticResource ....
由於您尚未在xaml中為所選項目或IsSelected指定任何綁定,因此,當在VM中更改屬性時,視圖未更新。 為了更新視圖,您將必須為ItemsControl的SelectedItem屬性提供一個綁定。
從綁定中刪除MusicalNotation前綴。
{Binding Path=IsSelected, ...
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