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Getting started

This article demonstrates a simple image gallery implemented with TouchManager and demonstrates the basic usage of the manager.

TouchManager requires the Telerik.Windows.Controls assembly to be referenced in the project.

First, we can create the UI of the gallery (Example 1). We will use one panel to hold several Image elements that will represent the gallery with the small images (the thumbnails). Then we can add another panel that will display the selected image.

Example 1: Defining the UI of the TouchManager example

<Window x:Class="WpfApplication2.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"&#13;    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"&#13;    xmlns:telerik="http://schemas.telerik.com/2008/xaml/presentation"&#13;    Title="MainWindow">
    <Grid Background="#323232">
        <Border x:Name="galleryContainer"
                Background="#E4E4E4" 
                Width="800" 
                Height="320">
            <Border.Clip>
                <RectangleGeometry Rect="0, 0, 800, 320"/>
            </Border.Clip>
            <StackPanel x:Name="galleryPanel" Orientation="Horizontal">
                <Image Source="Images/001.jpg" Height="320" Stretch="UniformToFill" Width="150" Margin="5 0 5 0" />
                <Image Source="Images/002.jpg" Height="320" Stretch="UniformToFill" Width="150" Margin="5 0 5 0" />
                <Image Source="Images/003.jpg" Height="320" Stretch="UniformToFill" Width="150" Margin="5 0 5 0" />
                <Image Source="Images/004.jpg" Height="320" Stretch="UniformToFill" Width="150" Margin="5 0 5 0" />
                <Image Source="Images/005.jpg" Height="320" Stretch="UniformToFill" Width="150" Margin="5 0 5 0" />
                <Image Source="Images/006.jpg" Height="320" Stretch="UniformToFill" Width="150" Margin="5 0 5 0" />
                <Image Source="Images/007.jpg" Height="320" Stretch="UniformToFill" Width="150" Margin="5 0 5 0" />
                <Image Source="Images/008.jpg" Height="320" Stretch="UniformToFill" Width="150" Margin="5 0 5 0" />
                <Image Source="Images/009.jpg" Height="320" Stretch="UniformToFill" Width="150" Margin="5 0 5 0" />
                <Image Source="Images/010.jpg" Height="320" Stretch="UniformToFill" Width="150" Margin="5 0 5 0" />
                <Image Source="Images/011.jpg" Height="320" Stretch="UniformToFill" Width="150" Margin="5 0 5 0" />                
            </StackPanel>
        </Border>

        <Border x:Name="largeImageContainer" Visibility="Collapsed" Width="500" Height="500">
            <Border.Clip>
                <RectangleGeometry Rect="0, 0, 500, 500"/>
            </Border.Clip>               
            <Image x:Name="largeImage" Stretch="UniformToFill" />
        </Border>
    </Grid>
</Window>

This is the frame over which we will implement the touch interactions - swipe and tap.

Here is an image that demonstrates the view:
Getting Started 01

Let us start by implementing the swipe of the gallery items. We can do that by handling the swipe and swipe inertia events of TouchManager. Example 2 demonstrates how to subscribe to the events:

Example 2: Subscribing to TouchManager events

TouchManager.AddSwipeStartedEventHandler(this.galleryContainer, new TouchEventHandler(OnGallerySwipeStarted));
TouchManager.AddSwipeEventHandler(this.galleryContainer, new SwipeEventHandler(OnGallerySwipe));
TouchManager.AddSwipeFinishedEventHandler(this.galleryContainer, new TouchEventHandler(OnGallerySwipeFinished));

TouchManager.AddSwipeInertiaStartedEventHandler(this.galleryContainer, new RadRoutedEventHandler(OnGallerySwipeInertiaStarted));
TouchManager.AddSwipeInertiaEventHandler(this.galleryContainer, new SwipeInertiaEventHandler(OnGallerySwipeInertia));
TouchManager.AddSwipeInertiaFinishedEventHandler(this.galleryContainer, new RadRoutedEventHandler(OnGallerySwipeInertiaFinished));
TouchManager.AddSwipeStartedEventHandler(Me.galleryContainer, New TouchEventHandler(AddressOf OnGallerySwipeStarted))
TouchManager.AddSwipeEventHandler(Me.galleryContainer, New SwipeEventHandler(AddressOf OnGallerySwipe))
TouchManager.AddSwipeFinishedEventHandler(Me.galleryContainer, New TouchEventHandler(AddressOf OnGallerySwipeFinished))

TouchManager.AddSwipeInertiaStartedEventHandler(Me.galleryContainer, New RadRoutedEventHandler(AddressOf OnGallerySwipeInertiaStarted))
TouchManager.AddSwipeInertiaEventHandler(Me.galleryContainer, New SwipeInertiaEventHandler(AddressOf OnGallerySwipeInertia))
TouchManager.AddSwipeInertiaFinishedEventHandler(Me.galleryContainer, New RadRoutedEventHandler(AddressOf OnGallerySwipeInertiaFinished))

The logic for the swipe action will be implemented in the Swipe and SwipeInertia event handlers. We can place the implementation in a separate method and use it in the handlers.

Example 3: Event handlers implementation

private void OnGallerySwipe(object sender, SwipeEventArgs args)
{
    args.Handled = true;
    this.MoveGallery(args.HorizontalChange);
}   

private void OnGallerySwipeInertia(object sender, SwipeInertiaEventArgs args)
{
    args.Handled = true;
    this.MoveGallery(args.HorizontalChange);
}

private void MoveGallery(double horizontalOffset)
{
    var margin = this.galleryPanel.Margin;
    var newLeft = margin.Left + horizontalOffset;
    newLeft = Math.Min(newLeft, 0);
    newLeft = Math.Max(newLeft, this.galleryContainer.ActualWidth - this.galleryPanel.ActualWidth);
    this.galleryPanel.Margin = new Thickness(newLeft, margin.Top, margin.Right, margin.Bottom);
}
Private Sub OnGallerySwipe(sender As Object, args As SwipeEventArgs)
    args.Handled = True
    Me.MoveGallery(args.HorizontalChange)
End Sub

Private Sub OnGallerySwipeInertia(sender As Object, args As SwipeInertiaEventArgs)
    args.Handled = True
    Me.MoveGallery(args.HorizontalChange)
End Sub

Private Sub MoveGallery(horizontalOffset As Double)
    Dim margin = Me.galleryPanel.Margin
    Dim newLeft = margin.Left + horizontalOffset
    newLeft = Math.Min(newLeft, 0)
    newLeft = Math.Max(newLeft, Me.galleryContainer.ActualWidth - Me.galleryPanel.ActualWidth)
    Me.galleryPanel.Margin = New Thickness(newLeft, margin.Top, margin.Right, margin.Bottom)
End Sub

Although we are working directly only with the Swipe and SwipeInertia events, we are going to handle the related events for consistency - SwipeStarted, SwipeFinisihed, SwipeInertiaStarted and SwipeInertiaFinished.

Example 4: Event handlers implementation

private void OnGallerySwipeStarted(object sender, TouchEventArgs args)
{
    args.Handled = true;
}

private void OnGallerySwipeFinished(object sender, TouchEventArgs args)
{
    args.Handled = true;
}

private void OnGallerySwipeInertiaStarted(object sender, RadRoutedEventArgs e)
{            
    e.Handled = true;            
}

private void OnGallerySwipeInertiaFinished(object sender, RadRoutedEventArgs e)
{
    e.Handled = true;
}
Private Sub OnGallerySwipeStarted(sender As Object, args As TouchEventArgs)
    args.Handled = True
End Sub

Private Sub OnGallerySwipeFinished(sender As Object, args As TouchEventArgs)
    args.Handled = True
End Sub

Private Sub OnGallerySwipeInertiaStarted(sender As Object, e As RadRoutedEventArgs)
    e.Handled = True
End Sub

Private Sub OnGallerySwipeInertiaFinished(sender As Object, e As RadRoutedEventArgs)
    e.Handled = True
End Sub

The SwipeInertia event won't be fired unless the SwipeInertiaStarted is handled.
args.Handled=true

Now when you swipe horizontally through the gallery, the images will scroll.

See Also

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