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[英]Update view when item's property of ObservableCollection is changed
[英]How to make an ObservableCollection update when an item property is changed
我已經看過這個問題很多次了(並回答了),但我似乎仍然無法弄清楚我所缺少的是什么...
我有一個帶有復選框列表的窗口,我希望能夠從后台隱藏代碼動態地啟用/禁用列表中的復選框。 為此,我有幾個單選按鈕,它們調用一個代碼隱藏函數來切換VisibleFeatures集合中第一個條目的“ Enabled”屬性。 理想情況下,這將導致第一個復選框+文本啟用/禁用,但不會發生UI更改。
我究竟做錯了什么?
ViewModel:
public class MyFeature
{
private bool _supported;
private bool _enabled;
private bool _selected;
public string Name { get; set; }
public bool Supported
{
get { return _supported; }
set { _supported = value; NotifyPropertyChanged("Supported"); }
}
public bool Enabled
{
get { return _enabled; }
set { _visible = value; NotifyPropertyChanged("Enabled"); }
}
public bool Selected
{
get { return _selected; }
set { _selected = value; NotifyPropertyChanged("Selected"); }
}
public MyFeature(string name)
{
Name = name;
_supported = false;
_enabled = false;
_selected = false;
}
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
public ObservableCollection<MyFeature> VisibleFeatures { get; set; }
void VisibleFeatures_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
if (e.NewItems != null)
foreach (MyFeature item in e.NewItems)
item.PropertyChanged += MyFeature_PropertyChanged;
if (e.OldItems != null)
foreach (MyFeature item in e.OldItems)
item.PropertyChanged -= MyFeature_PropertyChanged;
}
void MyFeature_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
// NotifyPropertyChanged() defined again elsewhere in the class
NotifyPropertyChanged("VisibleFeatures");
}
public Init()
{
VisibleFeatures = new ObservableCollection<MyFeature>();
VisibleFeatures.CollectionChanged += VisibleFeatures_CollectionChanged;
VisibleFeatures.Add(new MyFeature("Feature1"));
VisibleFeatures.Add(new MyFeature("Feature2"));
...
}
XAML:
<StackPanel>
<ListView ItemsSource="{Binding VisibleFeatures}">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel IsEnabled="{Binding Enabled, Mode=TwoWay}">
<CheckBox IsChecked="{Binding Selected, Mode=TwoWay}">
<TextBlock Text="{Binding Name}" />
</CheckBox>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListView>
</StackPanel>
您的類MyFeature需要聲明它實現了INotifyPropertyChanged
接口。 否則,XAML將不會生成任何偵聽器來偵聽您的屬性更改通知。
此外,從您的示例中,我看不到通知VisibleFeatures
更改。
從INotifyPropertyChanged接口派生您的類“ MyFeature”。
為了反映視圖中可觀察集合中所做的運行時更改,必須從INotifyPropertyChanged接口派生viewmodel類(此處為MyFeature類)。
另外,建議在任何使用綁定屬性的地方都使用相同的實例,而不要創建新的實例。
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