在 WPF 中拖放 TabItems？
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Drag and Drop TabItems in WPF?
提问by Jason Axelrod
So I found this answered questions: Is it possible to rearrange tab items in tab control in wpf?
所以我发现了这个问题的答案： Is it possible to rerange tab items in tab control in wpf?
Using the information in that thread, I set it all up in my application:
使用该线程中的信息，我在我的应用程序中进行了全部设置：
<TabControl x:Name="tabControl">
<TabControl.Resources>
<Style TargetType="TabItem">
<Setter Property="AllowDrop" Value="True"/>
<EventSetter Event="PreviewMouseMove" Handler="TabItem_Drag"/>
<EventSetter Event="Drop" Handler="TabItem_Drop"/>
</Style>
</TabControl.Resources>
</TabControl>
And the code:
和代码：
private void TabItem_Drag(object sender, MouseEventArgs e)
{
var tabItem = e.Source as TabItem;
if (tabItem == null)
return;
if (Mouse.PrimaryDevice.LeftButton == MouseButtonState.Pressed)
DragDrop.DoDragDrop(tabItem, tabItem, DragDropEffects.All);
}
private void TabItem_Drop(object sender, DragEventArgs e)
{
var tabItemTarget = e.Source as TabItem;
var tabItemSource = e.Data.GetData(typeof(TabItem)) as TabItem;
if (!tabItemTarget.Equals(tabItemSource))
{
int sourceIndex = tabControl.Items.IndexOf(tabItemSource);
int targetIndex = tabControl.Items.IndexOf(tabItemTarget);
tabControl.Items.Remove(tabItemSource);
tabControl.Items.Insert(targetIndex, tabItemSource);
tabControl.Items.Remove(tabItemTarget);
tabControl.Items.Insert(sourceIndex, tabItemTarget);
tabControl.SelectedIndex = targetIndex;
}
}
The problem is, when I drop the tab, I get the following error at
问题是，当我放下选项卡时，出现以下错误
if (!tabItemTarget.Equals(tabItemSource))
An exception of type 'System.NullReferenceException' occurred in Scoreboard Assistant.exe but was not handled in user code
Additional information: Object reference not set to an instance of an object.
Scoreboard Assistant.exe 中出现类型为“System.NullReferenceException”的异常，但未在用户代码中处理
附加信息：未将对象引用设置为对象的实例。
When I click continue, I get the following error at
当我单击继续时，出现以下错误
DragDrop.DoDragDrop(tabItem, tabItem, DragDropEffects.All);
An unhandled exception of type 'System.NullReferenceException' occurred in PresentationCore.dll
Additional information: Object reference not set to an instance of an object.
PresentationCore.dll 中发生类型为“System.NullReferenceException”的未处理异常
附加信息：未将对象引用设置为对象的实例。
And then the program dies. What am I doing wrong?
然后程序就死了。我究竟做错了什么？
* EDIT *
* 编辑 *
Okay, I figured out what the issue is; I just need help fixing it. If the tab item is created as follows it works perfectly fine:
好的，我想出了问题所在；我只是需要帮助修复它。如果按如下方式创建选项卡项目，则它可以正常工作：
<TabItem Header="TabItem"/>
However, my tabs are being created as follows:
但是，我的标签创建如下：
<TabItem>
<TabItem.Header>
<StackPanel Orientation="Horizontal">
<Image Source="images/text.png" />
<TextBlock Text="Text"/>
</StackPanel>
</TabItem.Header>
</TabItem>
As you can see, I am using a stackpanel to have an icon in the tab header. The problem seems to be that when I drag and drop the panel, instead of the e.Sourcebeing read as the tabitem, its reading the textblock within the stackpanel of the tabitem. How would I fix this?
如您所见，我使用堆栈面板在选项卡标题中有一个图标。问题似乎是，当我拖放面板时，它不是将面板e.Source读取为 tabitem，而是读取 tabitem 堆栈面板内的文本块。我将如何解决这个问题？
采纳答案by Dennis
Since the visual tree of TabItemheader can be rather complex, you can't guarantee, that drop target will be a TabIteminstance (that's what happening in your code).
由于TabItem标题的可视化树可能相当复杂，因此您无法保证放置目标将是一个TabItem实例（这就是您的代码中发生的情况）。
But you can find TabItemvia exploring visual tree:
但是你可以TabItem通过探索视觉树找到：
private TabItem GetTargetTabItem(object originalSource)
{
var current = originalSource as DependencyObject;
while (current != null)
{
var tabItem = current as TabItem;
if (tabItem != null)
{
return tabItem;
}
current = VisualTreeHelper.GetParent(current);
}
return null;
}
private void TabItem_Drop(object sender, DragEventArgs e)
{
var tabItemTarget = GetTargetTabItem(e.OriginalSource);
if (tabItemTarget != null)
{
var tabItemSource = (TabItem)e.Data.GetData(typeof(TabItem));
if (tabItemTarget != tabItemSource)
{
// the rest of your code
}
}
}
