Silverlight Tip of the Day #82 – How to Implement Double Click
Silverlight currently has full mouse support for single click. However, double click is a another story. In this tip I will show you how to implement double click. You can apply this technique for an individual control or even your entire page.
The key thing to do is to start a DispatcherTimer timer once a left mouse click event has been received. If another mouse click is intercepted before the double click time interval has passed then a double click has occurred. This interval is typically set to be around 200 milliseconds. Once 200 milliseconds has passed the timer is stopped and disabled until another mouse click is received.
To start, let’s create our timer and add a listener for the MouseLeftButtonDown event.
DispatcherTimer _doubleClickTimer;
Image _lastImage = null;
public Page()
{
InitializeComponent();
_doubleClickTimer = new DispatcherTimer();
_doubleClickTimer.Interval = new TimeSpan(0, 0, 0, 0, 200);
_doubleClickTimer.Tick += new EventHandler(DoubleClick_Timer);
this.MouseLeftButtonDown += new MouseButtonEventHandler(Page_MouseLeftButtonDown);
}
// too much time has passed for it to be a double click.
void DoubleClick_Timer(object sender, EventArgs e)
{
_doubleClickTimer.Stop();
}
Now, in the Page_MouseLeftButtonDown() method we:
- Check if the timer is enabled.
- If it is enabled already, then we have already clicked once and have made a double click.
- If is it not enabled start the timer.
void Page_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
if (_doubleClickTimer.IsEnabled)
{
// a double click has occured
_doubleClickTimer.Stop();
Image catImg = new Image();
Uri uri = new Uri("cat.png", UriKind.Relative);
ImageSource imgSource = new
System.Windows.Media.Imaging.BitmapImage(uri);
catImg.Source = imgSource;
catImg.SetValue(Canvas.LeftProperty,(double) e.GetPosition(LayoutRoot).X-90);
catImg.SetValue(Canvas.TopProperty, (double)e.GetPosition(LayoutRoot).Y-113);
if(null != _lastImage)
MainCanvas.Children.Remove(_lastImage);
MainCanvas.Children.Add(catImg);
_lastImage = catImg;
}
else
{
_doubleClickTimer.Start();
}
}
Here is a demo of this code:
Thank you,
--Mike Snow
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