GotoItemByIndex Method

Summary

Scroll to the top-left of an item giving its index.

Syntax

C++

public virtual void GotoItemByIndex( 
   int index 
)

Public Overridable Sub GotoItemByIndex( 
   ByVal index As Integer 
)

public:  
   virtual void GotoItemByIndex( 
      int index 
   )

Parameters

index

The 0-based index of the item

Remarks

To go to an item, use GotoItem, to go to an item by its index, use GotoItemByIndex.

The "GoTo" methods scrolls the viewer so the top-left portion of the item is visible in the current control boundary without changing the other transformation properties.

To ensure that an item is visible, use EnsureItemVisible, to ensure an item is visible giving its index, use EnsureItemVisibleByIndex.

The "Ensure" methods scrolls the viewer the minimum required to ensure the item is fully visible in the current control boundary without changing the other transformation property. If the item is already fully visible, then nothing happens. If the item is larger than the current control boundary, then the viewer will scrolls the minimum amount required where any of the edges (top-left, top-right, bottom-left or bottom-right) is visible.

For more information refer to Image Viewer Layouts, Image Viewer Appearance, Image Viewer Items, Image Viewer Transformation, and Image Viewer Bounds and Transform.

Example

This example will add a few items to the viewer and then allows the user to go to an item.

Run the demo and click the Example button.

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 LeadtoolsExamples.Common; 
using Leadtools.ImageProcessing; 
using Leadtools.ImageProcessing.Color; 
 
public void ImageViewerGotoItemByIndex_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.ItemPadding = new Padding(8, 8, 8, 20); 
   _imageViewer.ImageBorderThickness = 1; 
 
   // 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); 
         } 
 
         item.Text = string.Format("Item {0}", page - 1); 
         _imageViewer.Items.Add(item); 
      } 
   } 
 
   // Add a combobox control to show the items 
   var comboBox = new ComboBox(); 
   comboBox.Top = _label.Bottom; 
   if (_label.Parent != null) 
   { 
      _label.Parent.Controls.Add(comboBox); 
   } 
 
   // Add an entry for each item to the combo box 
   foreach (var item in _imageViewer.Items) 
      comboBox.Items.Add(item.Text); 
 
   // When the user selects an item from the combo box ... 
   comboBox.SelectedIndexChanged += (sender, e) => 
   { 
      // Get the corresponding item index... 
      var index = comboBox.SelectedIndex; 
      // And go to it 
      _imageViewer.GotoItemByIndex(index); 
   }; 
}

Imports Leadtools 
Imports Leadtools.Controls 
Imports Leadtools.Codecs 
Imports Leadtools.Drawing 
Imports Leadtools.ImageProcessing 
Imports Leadtools.ImageProcessing.Color 
Imports LeadtoolsControlsExamples.LeadtoolsExamples.Common 
 
Public Sub ImageViewerGotoItemByIndex_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.ItemPadding = New Padding(8, 8, 8, 20) 
   _imageViewer.ImageBorderThickness = 1 
 
   ' 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 
 
         item.Text = String.Format("Item {0}", page - 1) 
         _imageViewer.Items.Add(item) 
      Next page 
   End Using 
 
   ' Add a combobox control to show the items 
   Dim comboBox As New ComboBox() 
   comboBox.Top = _label.Bottom 
   _label.Parent.Controls.Add(comboBox) 
 
   ' Add an entry for each item to the combo box 
   For Each item As ImageViewerItem In _imageViewer.Items 
      comboBox.Items.Add(item.Text) 
   Next item 
 
   ' When the user selects an item from the combo box ... 
   AddHandler comboBox.SelectedIndexChanged, 
   Sub(sender, e) 
      ' Get the corresponding item index... 
      Dim index As Integer = comboBox.SelectedIndex 
      ' And go to it 
      _imageViewer.GotoItemByIndex(index) 
   End Sub 
End Sub

Requirements

Target Platforms

Reference

ImageViewer Class

ImageViewer Members

Leadtools.Controls Namespace

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Help Version 20.0.2020.4.3

Leadtools.Controls Assembly

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