C# 阻止TabControl重新创建其子项
我有一个绑定到C# 阻止TabControl重新创建其子项,c#,wpf,mvvm,datatemplate,tabcontrol,C#,Wpf,Mvvm,Datatemplate,Tabcontrol,我有一个绑定到TabControl的视图模型的IList。此IList在TabControl的生命周期内不会更改 <TabControl ItemsSource="{Binding Tabs}" SelectedIndex="0" > <TabControl.ItemContainerStyle> <Style TargetType="TabItem"> <Setter Property="Content"
TabControl
的视图模型的IList
。此IList
在TabControl
的生命周期内不会更改
<TabControl ItemsSource="{Binding Tabs}" SelectedIndex="0" >
<TabControl.ItemContainerStyle>
<Style TargetType="TabItem">
<Setter Property="Content" Value="{Binding}" />
</Style>
</TabControl.ItemContainerStyle>
</TabControl>
DataTemplate中指定的每个视图都是资源密集型视图,因此我宁愿只创建一次每个视图,但在切换选项卡时,会调用相关视图的构造函数。据我所知,这是TabControl
的预期行为,但我不清楚调用构造函数的机制是什么
我已经看过了,但是那里提供的解决方案需要我绑定到不需要的视图。默认情况下,
TabControl
共享一个面板来呈现其内容。要做您想要做的事情(以及许多其他WPF开发人员),您需要像这样扩展TabControl
:
TabControlEx.cs
[TemplatePart(Name = "PART_ItemsHolder", Type = typeof(Panel))]
public class TabControlEx : TabControl
{
private Panel ItemsHolderPanel = null;
public TabControlEx()
: base()
{
// This is necessary so that we get the initial databound selected item
ItemContainerGenerator.StatusChanged += ItemContainerGenerator_StatusChanged;
}
/// <summary>
/// If containers are done, generate the selected item
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void ItemContainerGenerator_StatusChanged(object sender, EventArgs e)
{
if (this.ItemContainerGenerator.Status == GeneratorStatus.ContainersGenerated)
{
this.ItemContainerGenerator.StatusChanged -= ItemContainerGenerator_StatusChanged;
UpdateSelectedItem();
}
}
/// <summary>
/// Get the ItemsHolder and generate any children
/// </summary>
public override void OnApplyTemplate()
{
base.OnApplyTemplate();
ItemsHolderPanel = GetTemplateChild("PART_ItemsHolder") as Panel;
UpdateSelectedItem();
}
/// <summary>
/// When the items change we remove any generated panel children and add any new ones as necessary
/// </summary>
/// <param name="e"></param>
protected override void OnItemsChanged(NotifyCollectionChangedEventArgs e)
{
base.OnItemsChanged(e);
if (ItemsHolderPanel == null)
return;
switch (e.Action)
{
case NotifyCollectionChangedAction.Reset:
ItemsHolderPanel.Children.Clear();
break;
case NotifyCollectionChangedAction.Add:
case NotifyCollectionChangedAction.Remove:
if (e.OldItems != null)
{
foreach (var item in e.OldItems)
{
ContentPresenter cp = FindChildContentPresenter(item);
if (cp != null)
ItemsHolderPanel.Children.Remove(cp);
}
}
// Don't do anything with new items because we don't want to
// create visuals that aren't being shown
UpdateSelectedItem();
break;
case NotifyCollectionChangedAction.Replace:
throw new NotImplementedException("Replace not implemented yet");
}
}
protected override void OnSelectionChanged(SelectionChangedEventArgs e)
{
base.OnSelectionChanged(e);
UpdateSelectedItem();
}
private void UpdateSelectedItem()
{
if (ItemsHolderPanel == null)
return;
// Generate a ContentPresenter if necessary
TabItem item = GetSelectedTabItem();
if (item != null)
CreateChildContentPresenter(item);
// show the right child
foreach (ContentPresenter child in ItemsHolderPanel.Children)
child.Visibility = ((child.Tag as TabItem).IsSelected) ? Visibility.Visible : Visibility.Collapsed;
}
private ContentPresenter CreateChildContentPresenter(object item)
{
if (item == null)
return null;
ContentPresenter cp = FindChildContentPresenter(item);
if (cp != null)
return cp;
// the actual child to be added. cp.Tag is a reference to the TabItem
cp = new ContentPresenter();
cp.Content = (item is TabItem) ? (item as TabItem).Content : item;
cp.ContentTemplate = this.SelectedContentTemplate;
cp.ContentTemplateSelector = this.SelectedContentTemplateSelector;
cp.ContentStringFormat = this.SelectedContentStringFormat;
cp.Visibility = Visibility.Collapsed;
cp.Tag = (item is TabItem) ? item : (this.ItemContainerGenerator.ContainerFromItem(item));
ItemsHolderPanel.Children.Add(cp);
return cp;
}
private ContentPresenter FindChildContentPresenter(object data)
{
if (data is TabItem)
data = (data as TabItem).Content;
if (data == null)
return null;
if (ItemsHolderPanel == null)
return null;
foreach (ContentPresenter cp in ItemsHolderPanel.Children)
{
if (cp.Content == data)
return cp;
}
return null;
}
protected TabItem GetSelectedTabItem()
{
object selectedItem = base.SelectedItem;
if (selectedItem == null)
return null;
TabItem item = selectedItem as TabItem;
if (item == null)
item = base.ItemContainerGenerator.ContainerFromIndex(base.SelectedIndex) as TabItem;
return item;
}
}
// Copy C# code from @Dennis's answer, and add the following property after the
// opening "<Style" tag (this sets the key for the style):
// x:Key="TabControlExStyle"
// Ensure that the namespace for this class is the same as your DataContext.
[TemplatePart(Name=“PART_ItemsHolder”,Type=typeof(Panel))]
公共类TabControlEx:TabControl
{
私有面板ItemsHolderPanel=null;
公共TabControlEx()
:base()
{
//这是必要的,以便我们获得初始数据绑定的选定项
ItemContainerGenerator.StatusChanged+=ItemContainerGenerator\u StatusChanged;
}
///
///如果容器已完成,则生成所选项目
///
///
///
私有void ItemContainerGenerator_状态已更改(对象发送者,事件参数e)
{
if(this.ItemContainerGenerator.Status==GeneratorStatus.ContainerGenerated)
{
this.ItemContainerGenerator.StatusChanged-=ItemContainerGenerator\u StatusChanged;
UpdateSelectedItem();
}
}
///
///获取ItemsHolder并生成所有子项
///
应用程序模板()上的公共重写无效
{
base.OnApplyTemplate();
ItemsHolderPanel=GetTemplateChild(“PART_ItemsHolder”)作为面板;
UpdateSelectedItem();
}
///
///当项目更改时,我们将删除所有生成的面板子项,并根据需要添加任何新的子项
///
///
已更改受保护的覆盖(NotifyCollectionChangedEventArgs e)
{
碱基(e);
如果(ItemsHolderPanel==null)
返回;
开关(电动)
{
案例通知CollectionChangedAction.Reset:
ItemsHolderPanel.Children.Clear();
打破
案例NotifyCollectionChangedAction。添加:
案例NotifyCollectionChangedAction。删除:
如果(例如,OldItems!=null)
{
foreach(e.OldItems中的var项)
{
ContentPresenter cp=FindChildContentPresenter(项目);
如果(cp!=null)
ItemsHolderPanel.Children.Remove(cp);
}
}
//不要对新项目做任何事情,因为我们不想这样做
//创建未显示的视觉效果
UpdateSelectedItem();
打破
案例通知收集更改操作。替换:
抛出新的NotImplementedException(“替换尚未实现”);
}
}
选择更改时受保护的覆盖无效(SelectionChangedEventArgs e)
{
基础。选举变更(e);
UpdateSelectedItem();
}
私有void UpdateSelectedItem()
{
如果(ItemsHolderPanel==null)
返回;
//如有必要,生成ContentPresenter
TabItem item=GetSelectedTabItem();
如果(项!=null)
CreateChildContentPresenter(项目);
//给正确的孩子看
foreach(ItemsHolderPanel.Children中的ContentPresenter子级)
Visibility=((child.tagas TabItem).IsSelected)?Visibility.Visible:Visibility.Collapsed;
}
私有ContentPresenter CreateChildContentPresenter(对象项)
{
如果(项==null)
返回null;
ContentPresenter cp=FindChildContentPresenter(项目);
如果(cp!=null)
返回cp;
//要添加的实际子项.cp.Tag是对TabItem的引用
cp=新的ContentPresenter();
cp.Content=(项目为TabItem)?(项目为TabItem)。内容:项目;
cp.ContentTemplate=此.SelectedContentTemplate;
cp.ContentTemplateSelector=此.SelectedContentTemplateSelector;
cp.ContentStringFormat=此.SelectedContentStringFormat;
cp.可见性=可见性。已折叠;
cp.Tag=(项为TabItem)?项:(this.ItemContainerGenerator.ContainerFromItem(项));
ItemsHolderPanel.Children.Add(cp);
返回cp;
}
私有ContentPresenter FindChildContentPresenter(对象数据)
{
如果(数据为TabItem)
数据=(数据作为TabItem)。内容;
如果(数据==null)
返回null;
如果(ItemsHolderPanel==null)
返回null;
foreach(ItemsHolderPanel.Children中的ContentPresenter cp)
{
if(cp.Content==数据)
返回cp;
}
返回null;
}
受保护的选项卡项GetSelectedTabItem()
{
object selectedItem=base.selectedItem;
如果(selectedItem==null)
返回null;
TabItem item=选择editem作为TabItem;
如果(项==null)
item=base.ItemContainerGenerator.ContainerFromIndex(base.SelectedIndex)作为TabItem;
退货项目;
}
}
XAML
<Style TargetType="{x:Type controls:TabControlEx}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TabControl}">
<Grid Background="{TemplateBinding Background}" ClipToBounds="True" KeyboardNavigation.TabNavigation="Local" SnapsToDevicePixels="True">
<Grid.ColumnDefinitions>
<ColumnDefinition x:Name="ColumnDefinition0" />
<ColumnDefinition x:Name="ColumnDefinition1" Width="0" />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition x:Name="RowDefinition0" Height="Auto" />
<RowDefinition x:Name="RowDefinition1" Height="*" />
</Grid.RowDefinitions>
<DockPanel Margin="2,2,0,0" LastChildFill="False">
<TabPanel x:Name="HeaderPanel" Margin="0,0,0,-1" VerticalAlignment="Bottom" Panel.ZIndex="1" DockPanel.Dock="Right"
IsItemsHost="True" KeyboardNavigation.TabIndex="1" />
</DockPanel>
<Border x:Name="ContentPanel" Grid.Row="1" Grid.Column="0"
Background="{TemplateBinding Background}"
BorderBrush="{TemplateBinding BorderBrush}"
BorderThickness="{TemplateBinding BorderThickness}"
KeyboardNavigation.DirectionalNavigation="Contained" KeyboardNavigation.TabIndex="2" KeyboardNavigation.TabNavigation="Local">
<Grid x:Name="PART_ItemsHolder" Margin="{TemplateBinding Padding}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" />
</Border>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
// Copy XAML from @Dennis's answer.
// Copy XAML from @Dennis's answer.
<TabControl
behaviours:TabControlBehaviour.DoSetSelectedTab="True"
IsSynchronizedWithCurrentItem="True">
<TabItem Header="Tab 1">
<TextBox>Hello</TextBox>
</TabItem>
<TabItem Header="Tab 2" >
<TextBox>Hello 2</TextBox>
</TabItem>
<sdm:TabControlEx
behaviours:TabControlBehaviour.DoSetSelectedTab="True"
IsSynchronizedWithCurrentItem="True"
Style="{StaticResource TabControlExStyle}">
<TabItem Header="Tab 1">
<TextBox>Hello</TextBox>
</TabItem>
<TabItem Header="Tab 2" >
<TextBox>Hello 2</TextBox>
</TabItem>
<dx:DXTabControl TabContentCacheMode="CacheAllTabs">
<dx:DXTabItem Header="Tab 1" >
<TextBox>Hello</TextBox>
</dx:DXTabItem>
<dx:DXTabItem Header="Tab 2">
<TextBox>Hello 2</TextBox>
</dx:DXTabItem>
</dx:DXTabControl>
<Window.Resources>
<converters:ContentGeneratorConverter x:Key="ContentGeneratorConverter"/>
<DataTemplate x:Key="ItemDataTemplate">
<StackPanel>
<TextBox Text="Try to change this text and choose another tab"/>
<TextBlock Text="{Binding}"/>
</StackPanel>
</DataTemplate>
<markup:Set x:Key="Items">
<system:String>Red</system:String>
<system:String>Green</system:String>
<system:String>Blue</system:String>
</markup:Set>
</Window.Resources>
public class ContentGeneratorConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
var control = new ContentControl {ContentTemplate = (DataTemplate) parameter};
control.SetBinding(ContentControl.ContentProperty, new Binding());
return control;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) =>
throw new NotImplementedException();
}
public class Set : List<object> { }
<TabControl
ItemsSource="{StaticResource Items}"
ContentTemplate="{StaticResource ItemDataTemplate}">
</TabControl>
<TabControl
ItemsSource="{StaticResource Items}">
<TabControl.ItemContainerStyle>
<Style TargetType="TabItem" BasedOn="{StaticResource {x:Type TabItem}}">
<Setter Property="Content" Value="{Binding Converter={StaticResource ContentGeneratorConverter}, ConverterParameter={StaticResource ItemDataTemplate}}"/>
</Style>
</TabControl.ItemContainerStyle>
</TabControl>