Silverlight自定义控件系列 – TreeView (3) 添加展开和收起事件

由于Writer嫌我文章过长，只能把上篇拆开两半了。以下是接着上篇的。

准备工作做完了，现在就要完成点击事件。

定义Expander和单击事件：

 1: /// <summary> 

 2: /// The togglebutton for expanding or collapsing the items when mouse left button clicked on it 

 3: /// </summary> 

 4: private ToggleButton expander;

 5:  

 1: /// <summary> 

 2: /// Gets or sets the toggle button Expander 

 3: /// </summary> 

 4: public ToggleButton Expander

 5: {

 6:  get 

 7: {

 8:  return this.expander;

 9: }

 10:  

 11:  set 

 12: {

 13:  if (this.expander != null)

 14: {

 15:  this.expander.Click -= new RoutedEventHandler(this.OnExpanderClick);

 16: }

 17:  

 18:  this.expander = value;

 19:  

 20:  if (this.expander != null)

 21: {

 22:  this.expander.IsChecked = new bool?(this.IsExpanded);

 23:  this.expander.Click += new RoutedEventHandler(this.OnExpanderClick);

 24: }

 25: }

 26: }

 27:  

 1: /// <summary> 

 2: /// Method occurs when mouse left button click on Expander 

 3: /// </summary> 

 4: /// <param name="sender">The source object</param> 

 5: /// <param name="e">The routed event arrguments</param> 

 6: private void OnExpanderClick(object sender, RoutedEventArgs e)

 7: {

 8:  bool flag = !this.IsExpanded;

 9:  this.IsExpanded = flag;

 10: }

 11:  

 1: /// <summary> 

 2: /// Method occurs when the expanded state has been changed 

 3: /// </summary> 

 4: /// <param name="handler">The target event handler</param> 

 5: /// <param name="args">The routed arrguments</param> 

 6: private void ChangeExpandedState(RoutedEventHandler handler, RoutedEventArgs args)

 7: {

 8:  ToggleButton button = this.Expander;

 9:  

 10:  if (button != null)

 11: {

 12: button.IsChecked = new bool?(this.IsExpanded);

 13: }

 14:  

 15:  this.UpdateVisualState(true);

 16:  this.RaiseEvent(handler, args);

 17: }

 18:  

接下来就是最后一步了，就是定义展开和收起事件，并把它们和刚才的准备工作结合起来

定义event handler：

 1: #region Events

 2:  

 3: /// <summary> 

 4: /// The expanded event 

 5: /// </summary> 

 6: public event RoutedEventHandler Expanded;

 7:  

 8: /// <summary> 

 9: /// The Collapsed event 

 10: /// </summary> 

 11: public event RoutedEventHandler Collapsed;

 12:  

 13: #endregion 

 14:  

定义事件：

 1: /// <summary> 

 2: /// To expand the children 

 3: /// </summary> 

 4: /// <param name="e">The routed event arrguments</param> 

 5: public void OnExpanded(RoutedEventArgs e)

 6: {

 7:  this.ChangeExpandedState(this.Expanded, e);

 8: }

 9:  

 10: /// <summary> 

 11: /// To collapse the children 

 12: /// </summary> 

 13: /// <param name="e">The routed event arrguments</param> 

 14: public void OnCollapsed(RoutedEventArgs e)

 15: {

 16:  this.ChangeExpandedState(this.Collapsed, e);

 17: }

 18:  

修改OnIsExpandedPropertyChanged方法：

 1: /// <summary> 

 2: /// Call back when IsExpanded property has been changed 

 3: /// </summary> 

 4: /// <param name="o">The target object</param> 

 5: /// <param name="e">The property changed event arrguments</param> 

 6: private static void OnIsExpandedPropertyChanged(DependencyObject o, DependencyPropertyChangedEventArgs e)

 7: {

 8:  FancyTreeViewItem item = o as FancyTreeViewItem;

 9:  bool newValue = (bool)e.NewValue;

 10:  RoutedEventArgs args = new RoutedEventArgs();

 11:  

 12:  if (newValue)

 13: {

 14: item.OnExpanded(args);

 15: }

 16:  else 

 17: {

 18: item.OnCollapsed(args);

 19: }

 20: }

 21:  

从模板中寻找Expander模块跟类中Expander按钮对应起来：

 1: /// <summary> 

 2: /// Override the function for banding template 

 3: /// </summary> 

 4: public override void OnApplyTemplate()

 5: {

 6:  this.Expander = this.GetTemplateChild("Expander") as ToggleButton;

 7:  base.OnApplyTemplate();

 8: }

 9:  

最后运行看下效果：

图3.1 节点收起的效果图

图3.2 节点展开的效果图