【发布时间】：2016-06-11 15:20:47
【问题描述】：
我正在慢慢学习 WPF 中的 MVVM。我编写了一个 GBA 游戏编辑器。编辑器由一个主窗口（Editor.xaml）组成，根据在菜单中选择的编辑器，我想显示相应的持久视图（切换时不是销毁器）。
我正在尝试使用一些关于 SO 的帖子中的 TabControlEx 类，例如 here 和 here。
但是我遇到了两个问题：首先，tabControlEx selectedItem 没有改变（固定见编辑），其次它似乎在 TabItem OnMouseOver 我失去了视图（具有 TabItem 的颜色背景属性将切换为白色）。
现在我很确定我或多或少地遗漏了一些明显的东西，但是作为 MVVM 的新手，我真的不知道去哪里找。所以这里是代码分解。
TabControlEx.cs
[TemplatePart(Name = "PART_ItemsHolder", Type = typeof(Panel))]
public class TabControlEx : System.Windows.Controls.TabControl
{
// Holds all items, but only marks the current tab's item as visible
private Panel _itemsHolder = null;
// Temporaily holds deleted item in case this was a drag/drop operation
private object _deletedObject = null;
public TabControlEx()
: base()
{
// this is necessary so that we get the initial databound selected item
this.ItemContainerGenerator.StatusChanged += ItemContainerGenerator_StatusChanged;
}
/// <summary>
/// if containers are done, generate the selected item
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
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();
_itemsHolder = 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 (_itemsHolder == null)
{
return;
}
switch (e.Action)
{
case NotifyCollectionChangedAction.Reset:
_itemsHolder.Children.Clear();
if (base.Items.Count > 0)
{
base.SelectedItem = base.Items[0];
UpdateSelectedItem();
}
break;
case NotifyCollectionChangedAction.Add:
case NotifyCollectionChangedAction.Remove:
// Search for recently deleted items caused by a Drag/Drop operation
if (e.NewItems != null && _deletedObject != null)
{
foreach (var item in e.NewItems)
{
if (_deletedObject == item)
{
// If the new item is the same as the recently deleted one (i.e. a drag/drop event)
// then cancel the deletion and reuse the ContentPresenter so it doesn't have to be
// redrawn. We do need to link the presenter to the new item though (using the Tag)
ContentPresenter cp = FindChildContentPresenter(_deletedObject);
if (cp != null)
{
int index = _itemsHolder.Children.IndexOf(cp);
(_itemsHolder.Children[index] as ContentPresenter).Tag =
(item is TabItem) ? item : (this.ItemContainerGenerator.ContainerFromItem(item));
}
_deletedObject = null;
}
}
}
if (e.OldItems != null)
{
foreach (var item in e.OldItems)
{
_deletedObject = item;
// We want to run this at a slightly later priority in case this
// is a drag/drop operation so that we can reuse the template
this.Dispatcher.BeginInvoke(DispatcherPriority.DataBind,
new Action(delegate ()
{
if (_deletedObject != null)
{
ContentPresenter cp = FindChildContentPresenter(_deletedObject);
if (cp != null)
{
this._itemsHolder.Children.Remove(cp);
}
}
}
));
}
}
UpdateSelectedItem();
break;
case NotifyCollectionChangedAction.Replace:
throw new NotImplementedException("Replace not implemented yet");
}
}
/// <summary>
/// update the visible child in the ItemsHolder
/// </summary>
/// <param name="e"></param>
protected override void OnSelectionChanged(SelectionChangedEventArgs e)
{
base.OnSelectionChanged(e);
UpdateSelectedItem();
}
/// <summary>
/// generate a ContentPresenter for the selected item
/// </summary>
void UpdateSelectedItem()
{
if (_itemsHolder == null)
{
return;
}
// generate a ContentPresenter if necessary
TabItem item = GetSelectedTabItem();
if (item != null)
{
CreateChildContentPresenter(item);
}
// show the right child
foreach (ContentPresenter child in _itemsHolder.Children)
{
child.Visibility = ((child.Tag as TabItem).IsSelected) ? Visibility.Visible : Visibility.Collapsed;
}
}
/// <summary>
/// create the child ContentPresenter for the given item (could be data or a TabItem)
/// </summary>
/// <param name="item"></param>
/// <returns></returns>
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));
_itemsHolder.Children.Add(cp);
return cp;
}
/// <summary>
/// Find the CP for the given object. data could be a TabItem or a piece of data
/// </summary>
/// <param name="data"></param>
/// <returns></returns>
ContentPresenter FindChildContentPresenter(object data)
{
if (data is TabItem)
{
data = (data as TabItem).Content;
}
if (data == null)
{
return null;
}
if (_itemsHolder == null)
{
return null;
}
foreach (ContentPresenter cp in _itemsHolder.Children)
{
if (cp.Content == data)
{
return cp;
}
}
return null;
}
/// <summary>
/// copied from TabControl; wish it were protected in that class instead of private
/// </summary>
/// <returns></returns>
protected TabItem GetSelectedTabItem()
{
object selectedItem = base.SelectedItem;
if (selectedItem == null)
{
return null;
}
if (_deletedObject == selectedItem)
{
}
TabItem item = selectedItem as TabItem;
if (item == null)
{
item = base.ItemContainerGenerator.ContainerFromIndex(base.SelectedIndex) as TabItem;
}
return item;
}
}
我的主要观点：
Editor.xaml
<Window.Resources>
<ResourceDictionary Source="Resources/GlobalDictionary.xaml" />
</Window.Resources>
<DockPanel>
<DockPanel DockPanel.Dock="Top" KeyboardNavigation.TabNavigation="None">
<Menu Height="20" KeyboardNavigation.TabNavigation="Cycle">
<MenuItem Header="{StaticResource MenuFile}">
<MenuItem Header="{StaticResource MenuOpen}" />
<MenuItem Header="{StaticResource MenuSave}" />
<MenuItem Header="{StaticResource MenuExit}" Command="{Binding Path=CloseCommand}" />
</MenuItem>
<MenuItem Header="{StaticResource MenuEditors}">
<MenuItem Header="{StaticResource MenuMonster}" Command="{Binding Path=OpenMonsterEditor}"/>
</MenuItem>
<MenuItem Header="{StaticResource MenuHelp}">
<MenuItem Header="{StaticResource MenuAbout}" />
<MenuItem Header="{StaticResource MenuContact}" />
</MenuItem>
</Menu>
</DockPanel>
<controls:TabControlEx ItemsSource="{Binding AvailableEditors}"
SelectedItem="{Binding CurrentEditor}"
Style="{StaticResource BlankTabControlTemplate}">
</controls:TabControlEx>
</DockPanel>
GlobalDictionary.xaml
<DataTemplate DataType="{x:Type vm:GBARomViewModel}">
<vw:GBARomView />
</DataTemplate>
<DataTemplate DataType="{x:Type vm:MonsterViewModel}">
<vw:MonsterView />
</DataTemplate>
<Style x:Key="BlankTabControlTemplate" TargetType="{x:Type control:TabControlEx}">
<Setter Property="SnapsToDevicePixels" Value="true"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type control:TabControlEx}">
<DockPanel>
<!-- This is needed to draw TabControls with Bound items -->
<StackPanel IsItemsHost="True" Height="0" Width="0" />
<Grid x:Name="PART_ItemsHolder" />
</DockPanel>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
我不确定以下是否正确，但每个视图范围 TabItem 如下。启动时的第一个视图正确显示。
GBARomView.xaml
<TabItem x:Class="FF6AE.View.GBARomView"
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:FF6AE.View"
mc:Ignorable="d"
d:DesignHeight="380" d:DesignWidth="646"
Background="BlueViolet">
<Grid >
</Grid>
</TabItem>
GBARomView.xaml.cs
public partial class GBARomView : TabItem
{
public GBARomView()
{
InitializeComponent();
}
}
最后是我的主要视图模型：
EDitorViewModel.cs
public class EditorViewModel: ViewModelBase
{
ViewModelBase _currentEditor;
ObservableCollection<ViewModelBase> _availableEditors;
RelayCommand _closeCommand;
RelayCommand _OpenMonsEditorCommand;
public EditorViewModel()
{
base.DisplayName = (string)AppInst.GetResource("EditorName");
_availableEditors = new ObservableCollection<ViewModelBase>();
_availableEditors.Add(new GBARomViewModel());
_availableEditors.Add(new MonsterViewModel());
_availableEditors.CollectionChanged += this.OnAvailableEditorsChanged;
_currentEditor = _availableEditors[0];
_currentEditor.PropertyChanged += this.OnSubEditorChanged;
}
public ViewModelBase CurrentEditor
{
get
{
if (_currentEditor == null)
{
_currentEditor = new GBARomViewModel();
_currentEditor.PropertyChanged += this.OnSubEditorChanged;
}
return _currentEditor;
}
set
{
_currentEditor = value;
// this is the thing I was missing
OnPropertyChanged("CurrentEditor");
}
}
void OnSubEditorChanged(object sender, PropertyChangedEventArgs e)
{
// For future use
}
public ObservableCollection<ViewModelBase> AvailableEditors
{
get
{
return _availableEditors;
}
}
void OnAvailableEditorsChanged(object sender, NotifyCollectionChangedEventArgs e)
{
// For future use
}
public ICommand OpenMonsterEditor
{
get
{
if (_OpenMonsEditorCommand == null)
_OpenMonsEditorCommand = new RelayCommand(param => this.OpenRequestOpen());
return _OpenMonsEditorCommand;
}
}
void OpenRequestOpen()
{
_currentEditor = _availableEditors[1];
}
public ICommand CloseCommand
{
get
{
if (_closeCommand == null)
_closeCommand = new RelayCommand(param => this.OnRequestClose());
return _closeCommand;
}
}
public event EventHandler RequestClose;
void OnRequestClose()
{
EventHandler handler = this.RequestClose;
if (handler != null)
handler(this, EventArgs.Empty);
}
}
所以基本上我迷失了为什么点击菜单中的怪物编辑器不会切换视图，尽管 currentEditor 值已更改（已修复）以及为什么鼠标悬停在 tabItem 上时我失去了背景测试视图的颜色（变为白色）。
任何帮助将不胜感激。提前致谢。
编辑：我在 CurrentEditor 的设置器中缺少 OnPropertyChanged("CurrentEditor");。
【问题讨论】：
标签： mvvm view persistence viewmodel tabcontrol