我在SO上发现了关于这个问题的多个问题，但是我仍然无法获得可靠的解决方案。这是我在阅读答案后想出来的。
的Xaml：
<Window x:Class="WpfApplication1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="MainWindow" Height="300" Width="300" x:Name="this">
<TabControl IsSynchronizedWithCurrentItem="True" ItemsSource="{Binding Tabs, ElementName=this}" x:Name="TabControl"/>
</Window>
代码背后：
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
var tabs = new ObservableCollection<string> {"Tab1", "Tab2", "Tab3"};
Tabs = CollectionViewSource.GetDefaultView(tabs);
Tabs.CurrentChanging += OnCurrentChanging;
Tabs.CurrentChanged += OnCurrentChanged;
Tabs.MoveCurrentToFirst();
CurrentTab = tabs.First();
}
private void OnCurrentChanging(object sender, CurrentChangingEventArgs e)
{
//only show message box when tab is changed by user input
if (!_cancelTabChange)
{
if (MessageBox.Show("Change tab?", "Message", MessageBoxButton.YesNo) == MessageBoxResult.No)
{
_cancelTabChange = true;
return;
}
}
_cancelTabChange = false;
}
private void OnCurrentChanged(object sender, EventArgs e)
{
if (!_cancelTabChange)
{
//Update current tab property, if user did not cancel transition
CurrentTab = (string)Tabs.CurrentItem;
}
else
{
//navigate back to current tab otherwise
Dispatcher.BeginInvoke(new Action(() => Tabs.MoveCurrentTo(CurrentTab)));
}
}
public string CurrentTab { get; set; }
public static readonly DependencyProperty TabsProperty = DependencyProperty.Register("Tabs", typeof(ICollectionView), typeof(MainWindow), new FrameworkPropertyMetadata(default(ICollectionView)));
public ICollectionView Tabs
{
get { return (ICollectionView)GetValue(TabsProperty); }
set { SetValue(TabsProperty, value); }
}
private bool _cancelTabChange;
}
基本上我想显示一条确认消息，当用户导航到不同的标签时，如果他点击了＃34; no＆＃34; - 中止过渡。但是这段代码不起作用。如果你在＆＃34; Tab2＆＃34;上多次点击，每次选择＆＃34; no＆＃34;在消息框中，它在某些时候停止工作：事件停止触发。如果您单击＆＃34; Tab3＆＃34;，则会再次触发事件，但如果您选择＆＃34;是＆＃34;它打开第二个选项卡，而不是第三个我无法搞清楚wtf是怎么回事。 ：）
有没有人在我的解决方案中看到错误？或者，当用户切换标签时，是否有更简单的方法来显示确认消息？我也愿意使用任何开源标签控件，它有一个正确的SelectionChanging事件。我找不到任何东西。
我正在使用.Net 4.0。
修改 如果我评论消息框：
private void OnCurrentChanging(object sender, CurrentChangingEventArgs e)
{
//only show message box when tab is changed by user input
if (!_cancelTabChange)
{
//if (MessageBox.Show("Change tab?", "Message", MessageBoxButton.YesNo) == MessageBoxResult.No)
//{
Debug.WriteLine("Canceled");
_cancelTabChange = true;
return;
//}
}
_cancelTabChange = false;
}
一切正常。怪异。
答案 0 :(得分：1)
似乎与
效果很好<TabControl ... yournamespace:SelectorAttachedProperties.IsSynchronizedWithCurrentItemFixEnabled="True" .../>
private void OnCurrentChanging(object sender, CurrentChangingEventArgs e)
{
if (MessageBox.Show("Change tab?", "Message", MessageBoxButton.YesNo) == MessageBoxResult.No)
{
e.Cancel = true;
}
}
public static class SelectorAttachedProperties
{
private static Type _ownerType = typeof(SelectorAttachedProperties);
#region IsSynchronizedWithCurrentItemFixEnabled
public static readonly DependencyProperty IsSynchronizedWithCurrentItemFixEnabledProperty =
DependencyProperty.RegisterAttached("IsSynchronizedWithCurrentItemFixEnabled", typeof(bool), _ownerType,
new PropertyMetadata(false, OnIsSynchronizedWithCurrentItemFixEnabledChanged));
public static bool GetIsSynchronizedWithCurrentItemFixEnabled(DependencyObject obj)
{
return (bool)obj.GetValue(IsSynchronizedWithCurrentItemFixEnabledProperty);
}
public static void SetIsSynchronizedWithCurrentItemFixEnabled(DependencyObject obj, bool value)
{
obj.SetValue(IsSynchronizedWithCurrentItemFixEnabledProperty, value);
}
private static void OnIsSynchronizedWithCurrentItemFixEnabledChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
Selector selector = d as Selector;
if (selector == null || !(e.OldValue is bool && e.NewValue is bool) || e.OldValue == e.NewValue)
return;
bool enforceCurrentItemSync = (bool)e.NewValue;
ICollectionView collectionView = null;
EventHandler itemsSourceChangedHandler = null;
itemsSourceChangedHandler = delegate
{
collectionView = selector.ItemsSource as ICollectionView;
if (collectionView == null)
collectionView = CollectionViewSource.GetDefaultView(selector);
};
SelectionChangedEventHandler selectionChangedHanlder = null;
selectionChangedHanlder = delegate
{
if (collectionView == null)
return;
if (selector.IsSynchronizedWithCurrentItem == true && selector.SelectedItem != collectionView.CurrentItem)
{
selector.IsSynchronizedWithCurrentItem = false;
selector.SelectedItem = collectionView.CurrentItem;
selector.IsSynchronizedWithCurrentItem = true;
}
};
if (enforceCurrentItemSync)
{
TypeDescriptor.GetProperties(selector)["ItemsSource"].AddValueChanged(selector, itemsSourceChangedHandler);
selector.SelectionChanged += selectionChangedHanlder;
}
else
{
TypeDescriptor.GetProperties(selector)["ItemsSource"].RemoveValueChanged(selector, itemsSourceChangedHandler);
selector.SelectionChanged -= selectionChangedHanlder;
}
}
#endregion IsSynchronizedWithCurrentItemFixEnabled
}
答案 1 :(得分：0)
由于某些原因，添加TabControl.Focus（）修复了一些事情：
private void OnCurrentChanged(object sender, EventArgs e)
{
if (!_cancelTabChange)
{
//Update current tab property, if user did not cancel transition
CurrentTab = (string)Tabs.CurrentItem;
}
else
{
//navigate back to current tab otherwise
Dispatcher.BeginInvoke(new Action(() =>
{
Tabs.MoveCurrentTo(CurrentTab);
TabControl.Focus();
}));
}
}
我仍然不知道地球上到底发生了什么。所以我很乐意接受这个问题的答案。
答案 2 :(得分：0)
必须遵守的人要求应用程序询问用户是否希望离开页面，所以这里是稍微改变的代码：
<input type="text" value="Hello, World!" id="myTextBox"/>
<input type="button" value="Lose Focus" id="loseFocusBtn"/>我认为这个小改变几乎可以满足您的需求。
答案 3 :(得分：0)
private void MainTabControl_OnSelectionChanged(object sender, SelectionChangedEventArgs e)
{
if (ReasonBecauseLeaveTabItemIsForbidden)
{
if (MainTabControl.SelectedIndex == IndexOfTabItem)
{
MessageBox.Show(SomeMessageWhyLeaveTabItemIsForbidden);
}
MainTabControl.SelectedIndex = IndexOfTabItem;
}
}
IndexOfTabItem - 禁用离开的TabItem的索引。
答案 4 :(得分：0)
在tabControl_SelectionChanged事件处理程序中：
if (e.OriginalSource == tabControl) //if this event fired from your tabControl
{
e.Handled = true;
if (!forbiddenPage.IsSelected) //User leaving the tab
{
if (forbiddenTest())
{
forbiddenPage.IsSelected = true;
MessageBox.Show("you must not leave this page");
}
}
请注意，设置forbiddenPage.IsSelected = true会导致循环，然后重新输入 此事件处理程序。但是，这一次，我们退出是因为所选页面是禁止页面。
答案 5 :(得分：-1)
有一个更简单的解决方案。将绑定添加到XAML中的选定项目：
<TabControl SelectedItem="{Binding SelectedTab}" ...
然后在视图模型中：
private Object _selectedTab;
public Object SelectedTab
{
get
{
return _selectedTab;
}
set
{
if (_selectedTab is ADR_Scanner.ViewModel.ConfigurationViewModel && _configurationViewModel.HasChanged)
{
System.Windows.Forms.MessageBox.Show("Please save the configuration changes", ADR_Scanner.App.ResourceAssembly.GetName().Name, System.Windows.Forms.MessageBoxButtons.OK, System.Windows.Forms.MessageBoxIcon.Error);
}
else
{
_selectedTab = value;
}
OnPropertyChanged("SelectedTab");
}
}
显然，您将ADR_Scanner.ViewModel.ConfigurationViewModel替换为您自己的视图模型类。最后确保在构造函数中初始化_selectedTab，否则TabControl将没有初始选择。