ActiveItem Property

C#
Visual Basic
Objective-C
Java

public virtual ImageViewerItem ActiveItem {get; set;}

'Declaration

Public Overridable Property ActiveItem As ImageViewerItem

Property Value

The active item of this image viewer. This value cannot be null.

For more information, refer to Image Viewer Items.

This example will use the viewer as a single-selection enabled list of images and shows how to track the current active item.

Start with the ImageViewer example, remove all the code inside the example function (search for the "// TODO: add example code here" comment) and insert the following code:

C#
Visual Basic
WinRT C#
WinRT JavaScript
Silverlight C#
Silverlight VB

Copy Code

Imports Leadtools
Imports Leadtools.Controls
Imports Leadtools.Codecs
Imports Leadtools.Drawing
Imports Leadtools.ImageProcessing
Imports Leadtools.ImageProcessing.Color

' Clear all the images already the viewer
_imageViewer.Items.Clear()
' Use vertical view layout
_imageViewer.ViewLayout = New ImageViewerVerticalViewLayout()
' Make sure the item size is larger than the image size (thumbnails mode)
_imageViewer.ItemSize = LeadSize.Create(200, 200)
_imageViewer.ImageBorderThickness = 1
' Change the active item background color
_imageViewer.ActiveItemBackgroundColor = Color.LightBlue
_imageViewer.SelectedItemBackgroundColor = Color.LightBlue
' Add 4 items to the viewer
Using codecs As New RasterCodecs()
   For page As Integer = 1 To 4
      Dim item As New ImageViewerItem()
      Dim fileName As String = Path.Combine(ImagesPath.Path, String.Format("ocr{0}.tif", page))

      ' Create a thumbnail from the image
      Using image As RasterImage = codecs.Load(fileName, page)
         item.Image = image.CreateThumbnail(180, 180, 24, RasterViewPerspective.TopLeft, RasterSizeFlags.Resample)
      End Using
      _imageViewer.Items.Add(item)
   Next page
End Using

' Add the interface mode to select items (single)
Dim selectItemsMode As New ImageViewerSelectItemsInteractiveMode()
selectItemsMode.SelectionMode = ImageViewerSelectionMode.Single
' Tell the mode to set the active item for us
selectItemsMode.AutoItemMode = ImageViewerAutoItemMode.AutoSetActive
_imageViewer.DefaultInteractiveMode = selectItemsMode

' Hook to the ActiveItemChanged event and update the label
AddHandler _imageViewer.ActiveItemChanged,
Sub(sender, e)
   Dim index As Integer = _imageViewer.Items.IndexOf(_imageViewer.ActiveItem)
   _label.Text = "ActiveIndex index is " & index.ToString()

using Leadtools;
using Leadtools.Controls;
using Leadtools.Codecs;
using Leadtools.Drawing;
using Leadtools.ImageProcessing;
using Leadtools.ImageProcessing.Color;

// Clear all the images already the viewer
_imageViewer.Items.Clear();
// Use vertical view layout
_imageViewer.ViewLayout = new ImageViewerVerticalViewLayout();
// Make sure the item size is larger than the image size (thumbnails mode)
_imageViewer.ItemSize = LeadSize.Create(200, 200);
_imageViewer.ImageBorderThickness = 1;
// Change the active item background color
_imageViewer.ActiveItemBackgroundColor = Color.LightBlue;
_imageViewer.SelectedItemBackgroundColor = Color.LightBlue;
// Add 4 items to the viewer
using (var codecs = new RasterCodecs())
{
   for (var page = 1; page <= 4; page++)
   {
      var item = new ImageViewerItem();
      var fileName = Path.Combine(ImagesPath.Path, string.Format("ocr{0}.tif", page));

      // Create a thumbnail from the image
      using (var image = codecs.Load(fileName, page))
      {
         item.Image = image.CreateThumbnail(180, 180, 24, RasterViewPerspective.TopLeft, RasterSizeFlags.Resample);
      }
      _imageViewer.Items.Add(item);
   }
}

// Add the interface mode to select items (single)
var selectItemsMode = new ImageViewerSelectItemsInteractiveMode();
selectItemsMode.SelectionMode = ImageViewerSelectionMode.Single;
// Tell the mode to set the active item for us
selectItemsMode.AutoItemMode = ImageViewerAutoItemMode.AutoSetActive;
_imageViewer.DefaultInteractiveMode = selectItemsMode;

// Hook to the ActiveItemChanged event and update the label
_imageViewer.ActiveItemChanged += (sender, e) =>
{
   var index = _imageViewer.Items.IndexOf(_imageViewer.ActiveItem);
   _label.Text = "ActiveIndex index is " + index.ToString();
};

Target Platforms

Reference

ImageViewer Class
ImageViewer Members