Cleanest single click + double click handling in Silverlight? - silverlight-3.0

Question

I've been finding various methods of dealing with double click and then the authors slap on some if code for handling single clicks. Is there a standard now in Silverlight 3 that everyone is using to handle both a single and a double click on listboxes?

Answer 1

If you use the Reactive Extensions (Rx) library the code to support double click is much simpler:
Observable.FromEvent<MouseButtonEventArgs>(myControl, "MouseLeftButtonDown").TimeInterval().Subscribe(evt =>
{
if (evt.Interval.TotalMilliseconds <= 300)
{
// Do something on double click
}
});

Answer 2

Write once use easily....
import YourProject.Utils; //must for using extentions
button1.AddDoubleClickHandler((s, e) =>
{
Debug.WriteLine("You can use this DoubleClick extention method
for any UIElement in SL !");
});
//Here is my util
namespace YourProject.Utils
{
public class DoubleClick
{
public DoubleClick()
{
this._lastClick = DateTime.Now;
}
private TimeSpan DoubleClickThreshold = TimeSpan.FromMilliseconds(450);
private DateTime _lastClick;
public event MouseButtonEventHandler MouseDoubleClick;
public void DoubleClicked(object sender, MouseButtonEventArgs e)
{
if (DateTime.Now - this._lastClick <= DoubleClickThreshold)
{
MouseDoubleClick(sender, e);
}
this._lastClick = DateTime.Now;
}
internal void AddHandler(UIElement ctl)
{
ctl.AddHandler(UIElement.MouseLeftButtonUpEvent, new MouseButtonEventHandler(this.DoubleClicked), true);
}
}
public static class DoubleClickExtentions
{
public static void AddDoubleClickHandler(this UIElement ctl, MouseButtonEventHandler MouseDoubleClick)
{
DoubleClick doubleClick = new DoubleClick();
doubleClick.MouseDoubleClick += MouseDoubleClick;
doubleClick.AddHandler(ctl);
}
}
}

Answer 3

I like this approach:
http://www.domagoj.pavlesic.com/DoubleClick-in-Silverlight
Pros: you have single click, double click and single click delayed events (so you can be sure, there will be no double click).

Answer 4

I've implemented a clean way to register for DoubleClick events based on the approaches of the following articles:
http://yinyangme.com/blog/post/The-simplest-way-to-detect-DoubleClick-in-Silverlight.aspx
http://www.domagoj.pavlesic.com/DoubleClick-in-Silverlight
To use it, you just need to register/unregister the handler through extension methods:
element.AddDoubleClickHandler(Element_DoubleClick);
element.RemoveDoubleClickHandler(Element_DoubleClick);
Here is the code:
using System;
using System.Windows;
using System.Windows.Input;
namespace System.Windows
{
public class DoubleClickHelper
{
private const long DoubleClickSpeed = 500;
private const double MaxMoveDistance = 10;
private static long lastClickTicks = 0;
private static Point lastPosition;
private static WeakReference lastSender;
internal static bool IsDoubleClick(object sender, MouseButtonEventArgs e)
{
Point position = e.GetPosition(null);
long clickTicks = DateTime.Now.Ticks;
long elapsedTicks = clickTicks - lastClickTicks;
long elapsedTime = elapsedTicks / TimeSpan.TicksPerMillisecond;
bool quickClick = (elapsedTime <= DoubleClickSpeed);
bool senderMatch = (lastSender != null && sender.Equals(lastSender.Target));
if (senderMatch && quickClick && DoubleClickHelper.Distance(position, lastPosition) <= MaxMoveDistance)
{
// Double click!
lastClickTicks = 0;
lastSender = null;
return true;
}
// Not a double click
lastClickTicks = clickTicks;
lastPosition = position;
if (!quickClick)
lastSender = new WeakReference(sender);
return false;
}
private static double Distance(Point pointA, Point pointB)
{
double x = pointA.X - pointB.X;
double y = pointA.Y - pointB.Y;
return Math.Sqrt(x * x + y * y);
}
public bool HasHandlers { get { return this.MouseDoubleClick != null; } }
private WeakReference target;
public event MouseButtonEventHandler MouseDoubleClick;
private void OnMouseDoubleClick(MouseButtonEventArgs args)
{
if (this.MouseDoubleClick != null && this.target.IsAlive)
this.MouseDoubleClick(this.target.Target, args);
}
public DoubleClickHelper(FrameworkElement target)
{
this.target = new WeakReference(target);
target.MouseLeftButtonDown += target_MouseLeftButtonDown;
}
void target_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
if (DoubleClickHelper.IsDoubleClick(sender, e))
this.OnMouseDoubleClick(e);
}
}
public static class DoubleClickExtension
{
public static DoubleClickHelper GetDoubleClickHelper(DependencyObject obj)
{
return (DoubleClickHelper)obj.GetValue(DoubleClickHelperProperty);
}
public static void SetDoubleClickHelper(DependencyObject obj, DoubleClickHelper value)
{
obj.SetValue(DoubleClickHelperProperty, value);
}
public static readonly DependencyProperty DoubleClickHelperProperty =
DependencyProperty.RegisterAttached("DoubleClickHelper", typeof(DoubleClickHelper), typeof(DoubleClickExtension), new PropertyMetadata(null));
public static void AddDoubleClickHandler(this FrameworkElement target, MouseButtonEventHandler handler)
{
DoubleClickHelper helper = target.GetValue(DoubleClickHelperProperty) as DoubleClickHelper;
if (helper == null)
{
helper = new DoubleClickHelper(target);
target.SetValue(DoubleClickHelperProperty, helper);
}
helper.MouseDoubleClick += handler;
}
public static void RemoveDoubleClickHandler(this FrameworkElement target, MouseButtonEventHandler handler)
{
DoubleClickHelper helper = target.GetValue(DoubleClickHelperProperty) as DoubleClickHelper;
if (helper == null) return;
helper.MouseDoubleClick -= handler;
if(!helper.HasHandlers)
target.SetValue(DoubleClickHelperProperty, null);
}
}
}

Answer 5

There is an easier way in Silverlight 5, which supports MouseButtonEventArgs.ClickCount. So, you can just attach a normal MouseLeftButtonDown handler, and check:
private void OnMouseLeftButtonDown(object sender, MouseButtonEventArgs args)
{
if (args.ClickCount == 1)
return;
// handle double-click
}

Answer 6

Here's a class I've implemented for controls and also a second derived class below for a treeview (Silverlight Toolkit). Just instantiate it with the control you want to check for double clicks and add a handler for the DoubleClicked event. It uses a timer to try to simulate a double-click event. You can change the delay if you think it will work better.
Public Class DoubleClickHelper
Public Event DoubleClicked(ByVal sender As FrameworkElement)
Private WithEvents UI As FrameworkElement
Sub New(ByRef UI As FrameworkElement)
Me.UI = UI
UI.AddHandler(UIElement.MouseLeftButtonDownEvent, New MouseButtonEventHandler(AddressOf UI_MouseLeftButtonDown), True)
InitTimer()
End Sub
Public Delay As Single = 0.2
Private _dblclick As Boolean = False
Private _timer As New System.Windows.Threading.DispatcherTimer()
Protected Property DoubleClick() As Boolean
Get
Return _dblclick
End Get
Set(ByVal value As Boolean)
_dblclick = value
InitTimer()
End Set
End Property
Private Sub InitTimer()
RemoveHandler _timer.Tick, AddressOf timer_Tick
_timer.Stop()
_timer = New System.Windows.Threading.DispatcherTimer()
_timer.Interval = TimeSpan.FromSeconds(Delay)
AddHandler _timer.Tick, AddressOf timer_Tick
_timer.Start()
End Sub
Protected Overridable Sub timer_Tick(ByVal sender As Object, ByVal e As EventArgs)
DoubleClick = False
End Sub
Protected Overridable Sub UI_MouseLeftButtonDown(ByVal sender As Object, ByVal e As System.Windows.Input.MouseButtonEventArgs) Handles UI.MouseLeftButtonDown
If DoubleClick Then
HandleDoubleClick(sender)
Else
HandleFirstClick(sender)
End If
End Sub
Protected Overridable Sub HandleDoubleClick(ByVal sender As FrameworkElement)
RaiseEvent DoubleClicked(sender)
End Sub
Protected Overridable Sub HandleFirstClick(ByVal sender As FrameworkElement)
DoubleClick = True
End Sub
End Class
Public Class TreeViewItemDoubleClickHelper
Inherits DoubleClickHelper
Private SameSelection As Boolean = False
Private WithEvents TreeView As TreeView = Nothing
Public Sub New(ByVal TreeView As TreeView)
MyBase.New(TreeView)
Me.TreeView = TreeView
End Sub
'This event happens after MouseLeftButtonDown
Private Sub TreeView_SelectedItemChanged(ByVal sender As Object, ByVal e As System.Windows.RoutedPropertyChangedEventArgs(Of Object)) Handles TreeView.SelectedItemChanged
SameSelection = e.OldValue Is e.NewValue
End Sub
Protected Overrides Sub UI_MouseLeftButtonDown(ByVal sender As Object, ByVal e As System.Windows.Input.MouseButtonEventArgs)
'MyBase.UI_MouseLeftButtonDown(sender, e)
If DoubleClick Or SameSelection Then
HandleDoubleClick(sender)
SameSelection = False
DoubleClick = False
Else
HandleFirstClick(sender)
End If
End Sub
End Class