SelectedItemsChanged Event

Summary

Occurs when any of the items inside this viewer selection state changes.

Syntax

C++

public event EventHandler SelectedItemsChanged

Public Event SelectedItemsChanged As EventHandler

public:  
   event EventHandler^ SelectedItemsChanged

Remarks

This event will occur when the value of ImageViewerItem.IsSelected of any of the items inside this image viewer changes. To get the selected items of the viewer:

Loop through the Items collection and check the IsSelected property of each item
Use the ImageViewerItems.GetSelected method that will return an array of the currently selected items.

Item selection state changes in many ways:

The IsSelected value of an item inside this viewer is changed programmatically.
If a selected item was removed from the viewer.
The ImageViewerItems.Select method is called.
The ImageViewerSelectItemsInteractiveMode is set in the viewer and is working.

When any of this occurs, the viewer will automatically re-renders the affected items and uses the "Selected" border, background and text color properties for any selected items. Besides this rendering behavior, the viewer does have treat selected items any differently and the selection state do not behave differently programmatically than any other item. Also there is no restriction on the number of items selected, you can select none, one or many items. For more information, refer to Image Viewer Items.

Example

This example will use the viewer as a multi-selection enabled list of images and shows how to track the current selected items.

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:

using Leadtools; 
using Leadtools.Controls; 
using Leadtools.Codecs; 
using Leadtools.Drawing; 
using Leadtools.ImageProcessing; 
using Leadtools.ImageProcessing.Color; 
 
 
public void SelectedItemsChanged_Example() 
{ 
 
   // 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 selected item background color 
   _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(LEAD_VARS.ImagesDir, 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 (multiple) 
   var selectItemsMode = new ImageViewerSelectItemsInteractiveMode(); 
   selectItemsMode.SelectionMode = ImageViewerSelectionMode.Multi; 
   _imageViewer.DefaultInteractiveMode = selectItemsMode; 
 
   // Hook to the SelectItemsChanged event and update the label 
   _imageViewer.SelectedItemsChanged += (sender, e) => 
   { 
      var sb = new StringBuilder(); 
      sb.Append("Selected indices:"); 
 
      // Get the selected items 
      var items = _imageViewer.Items.GetSelected(); 
      foreach (var item in items) 
         sb.Append(_imageViewer.Items.IndexOf(item) + " "); 
      _label.Text = sb.ToString(); 
   }; 
 
} 
 
static class LEAD_VARS 
{ 
   public const string ImagesDir = @"C:\LEADTOOLS21\Resources\Images"; 
}

Imports Leadtools 
Imports Leadtools.Controls 
Imports Leadtools.Codecs 
Imports Leadtools.Drawing 
Imports Leadtools.ImageProcessing 
Imports Leadtools.ImageProcessing.Color 
Imports LeadtoolsControlsExamples.LeadtoolsExamples.Common 
 
Public Sub SelectedItemsChanged_Example() 
   ' 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 selected item background color 
   _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 (multiple) 
   Dim selectItemsMode As New ImageViewerSelectItemsInteractiveMode() 
   selectItemsMode.SelectionMode = ImageViewerSelectionMode.Multi 
   _imageViewer.DefaultInteractiveMode = selectItemsMode 
 
   ' Hook to the SelectItemsChanged event and update the label 
   AddHandler _imageViewer.SelectedItemsChanged, 
   Sub(sender, e) 
      Dim sb As New StringBuilder() 
      sb.Append("Selected indices:") 
 
      ' Get the selected items 
      Dim items() As ImageViewerItem = _imageViewer.Items.GetSelected() 
      For Each item As ImageViewerItem In items 
         sb.Append(_imageViewer.Items.IndexOf(item) & " ") 
      Next item 
      _label.Text = sb.ToString() 
   End Sub 
End Sub

Event Data

Parameter	Type	Description
sender	object	The source of the event.

Requirements

Target Platforms

Reference

ImageViewer Class

ImageViewer Members

Leadtools.Controls Namespace

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Help Version 21.0.2021.7.2

Leadtools.Controls Assembly

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