我在试图从代码设置ItemsPanel以便实现virtualizengstackpanel时找到了您的文章。当我的单子上有成百上千个项目时,表现就糟透了。不管怎样。。我就是这样做的。
1) 自定义控件
--您也可以将此行为应用于普通组合框-在每个实例上,或通过样式。
--您还可以公开超时值,以便在xaml中重写。。
--而且,当下拉列表本身打开时,这似乎不起作用。不知道为什么。。从没调查过
1。。
public class KeyPressSelectionComboBox : ComboBox
{
private BindingExpression _bindingExpression;
public KeyPressSelectionComboBox()
: base()
{
Interaction.GetBehaviors(this).Add(new KeyPressSelectionBehavior());
Height = 22;
this.SelectionChanged += new SelectionChangedEventHandler(KeyPressSelectionComboBox_SelectionChanged);
}
void KeyPressSelectionComboBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
if (_bindingExpression == null)
{
_bindingExpression = this.GetBindingExpression(ComboBox.SelectedValueProperty);
}
else
{
if (this.GetBindingExpression(ComboBox.SelectedValueProperty) == null)
{
this.SetBinding(ComboBox.SelectedValueProperty, _bindingExpression.ParentBinding);
}
}
}
}
2。。。
/// <summary>
/// This behavior can be attached to a ListBox or ComboBox to
/// add keyboard selection
/// </summary>
public class KeyPressSelectionBehavior : Behavior<Selector>
{
private string keyDownHistory = string.Empty;
private double _keyDownTimeout = 2500;
private DateTime _lastKeyDownTime;
private DateTime LastKeyDownTime
{
get
{
if (this._lastKeyDownTime == null)
this._lastKeyDownTime = DateTime.Now;
return this._lastKeyDownTime;
}
set { _lastKeyDownTime = value; }
}
/// <summary>
/// Gets or sets the Path used to select the text
/// </summary>
public string SelectionMemberPath { get; set; }
/// <summary>
/// Gets or sets the Timeout (ms) used to reset the KeyDownHistory item search string
/// </summary>
public double KeyDownTimeout
{
get { return _keyDownTimeout; }
set { _keyDownTimeout = value; }
}
public KeyPressSelectionBehavior() { }
/// <summary>
/// Attaches to the specified object: subscribe on KeyDown event
/// </summary>
protected override void OnAttached()
{
base.OnAttached();
this.AssociatedObject.KeyDown += DoKeyDown;
}
void DoKeyDown(object sender, KeyEventArgs e)
{
// Create a list of strings and indexes
int index = 0;
IEnumerable<Item> list = null;
var path = SelectionMemberPath ??
this.AssociatedObject.DisplayMemberPath;
var evaluator = new BindingEvaluator();
if (path != null)
{
list = this.AssociatedObject.Items.OfType<object>()
.Select(item =>
{
// retrieve the value using the supplied Path
var binding = new Binding();
binding.Path = new PropertyPath(path);
binding.Source = item;
BindingOperations.SetBinding(evaluator,
BindingEvaluator.TargetProperty, binding);
var value = evaluator.Target;
return new Item
{
Index = index++,
Text = Convert.ToString(value)
};
});
}
else
{
list = this.AssociatedObject.Items.OfType<ListBoxItem>()
.Select(item => new Item
{
Index = index++,
Text = Convert.ToString(item.Content)
});
}
// Sort the list starting at next selectedIndex to the end and
// then from the beginning
list = list.OrderBy(item => item.Index <=
this.AssociatedObject.SelectedIndex ?
item.Index + this.AssociatedObject.Items.Count : item.Index);
// calculate how long has passed since the user typed a letter
var elapsedTime = DateTime.Now - this.LastKeyDownTime;
if (elapsedTime.TotalMilliseconds <= this.KeyDownTimeout)
{ /* if it's less than the timeout, add to the search string */
this.keyDownHistory += GetKeyValue(e);
}
else
{ /* otherwise replace it */
this.keyDownHistory = GetKeyValue(e);
}
// Find first starting with the search string
var searchText = this.keyDownHistory;
var first = list.FirstOrDefault(item =>
item.Text.StartsWith(searchText, StringComparison.InvariantCultureIgnoreCase));
if (first != null)
{ /* found */
this.AssociatedObject.SelectedIndex = first.Index;
}
else
{ /* not found - so reset the KeyDownHistory */
this.keyDownHistory = string.Empty;
}
// reset the last time a key was pressed
this.LastKeyDownTime = DateTime.Now;
}
/// <summary>
/// Gets the value of the pressed key,
/// specifically converting number keys from their "Dx" value to their expected "x" value
/// </summary>
/// <param name="e"></param>
/// <returns></returns>
private static string GetKeyValue(KeyEventArgs e)
{
string rValue = string.Empty;
switch (e.Key)
{
default:
rValue = e.Key.ToString();
break;
case Key.D0:
case Key.NumPad0:
rValue = (0).ToString();
break;
case Key.D1:
case Key.NumPad1:
rValue = (1).ToString();
break;
case Key.D2:
case Key.NumPad2:
rValue = (2).ToString();
break;
case Key.D3:
case Key.NumPad3:
rValue = (3).ToString();
break;
case Key.D4:
case Key.NumPad4:
rValue = (4).ToString();
break;
case Key.D5:
case Key.NumPad5:
rValue = (5).ToString();
break;
case Key.D6:
case Key.NumPad6:
rValue = (6).ToString();
break;
case Key.D7:
case Key.NumPad7:
rValue = (7).ToString();
break;
case Key.D8:
case Key.NumPad8:
rValue = (8).ToString();
break;
case Key.D9:
case Key.NumPad9:
rValue = (9).ToString();
break;
}
return rValue;
}
/// <summary>
/// Helper class
/// </summary>
private class Item
{
public int Index;
public string Text;
}
/// <summary>
/// Helper class used for property path value retrieval
/// </summary>
private class BindingEvaluator : FrameworkElement
{
public static readonly DependencyProperty TargetProperty =
DependencyProperty.Register(
"Target",
typeof(object),
typeof(BindingEvaluator), null);
public object Target
{
get { return GetValue(TargetProperty); }
set { SetValue(TargetProperty, value); }
}
}
}
