ActiveItemChanged Event

Summary

Occurs when the value of ActiveItem changes.

Syntax

C++/CLI

public event EventHandler ActiveItemChanged

public:  
   event EventHandler^ ActiveItemChanged

Remarks

For more information, refer to Image Viewer Items.

Example

using Leadtools; 
using Leadtools.Controls; 
using Leadtools.Codecs; 
using Leadtools.Drawing; 
using Leadtools.ImageProcessing; 
using Leadtools.ImageProcessing.Color; 
 
 
public ImageViewerForm _form = new ImageViewerForm(); 
public ImageViewer _imageViewer; 
 
public void ImageViewerActiveItemExample() 
{ 
   // Get the Form's ImageViewer control 
   _imageViewer = _form.ImageViewer; 
   // 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(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 (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 
   _imageViewer.ActiveItemChanged += (sender, e) => 
   { 
      var index = _imageViewer.Items.IndexOf(_imageViewer.ActiveItem); 
      Debug.WriteLine("ActiveIndex index is " + index.ToString()); 
   }; 
} 
 
static class LEAD_VARS 
{ 
   public const string ImagesDir = @"C:\LEADTOOLS23\Resources\Images"; 
}

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 23.0.2024.2.29

Leadtools.Controls Assembly

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Leadtools.Controls Namespace

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