activeItem Property

Summary

Active item of this image viewer.

Syntax
TypeScript
JavaScript
Object.defineProperty(ImageViewer.prototype, 'activeItem', 
	get: function(), 
	set: function(value) 
) 
activeItem: ImageViewerItem; 

Property Value

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

Remarks

For more information, refer to Image Viewer Items.

Example

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

ActiveItemChanged.ts
ImageViewer.ts
ActiveItemChanged.js
ImageViewer.js
ActiveItemChanged.html
import { ImageViewer_Example } from "../ImageViewer"; 
 
export class ImageViewer_ActiveItemChangedExample { 
   private viewerExample; 
   constructor() { 
      this.viewerExample = new ImageViewer_Example(this.run); 
   } 
 
   private run = (viewer: lt.Controls.ImageViewer) => { 
      // Clear all the images already the viewer 
      viewer.items.clear(); 
      // Use vertical view layout 
      viewer.viewLayout = new lt.Controls.ImageViewerVerticalViewLayout(); 
      // Make sure the item size is larger than the image size (thumbnails mode) 
      viewer.itemBorderThickness = 3; 
      // Change the active item background color 
      viewer.activeItemBorderColor = "forestgreen"; 
 
      // Add 4 items to the viewer 
      for (let page = 1; page <= 4; page++) { 
         const item: lt.Controls.ImageViewerItem = new lt.Controls.ImageViewerItem(); 
         const imageUrl: string = "https://demo.leadtools.com/images/png/ocr" + page.toString() + ".png"; 
         item.url = imageUrl; 
         viewer.items.add(item); 
      } 
 
      const panZoom: lt.Controls.ImageViewerPanZoomInteractiveMode = viewer.interactiveModes.findById(lt.Controls.ImageViewerInteractiveMode.panZoomModeId) as lt.Controls.ImageViewerPanZoomInteractiveMode; 
      // Tell the mode to set the active item for us 
      panZoom.autoItemMode = lt.Controls.ImageViewerAutoItemMode.autoSetActive; 
 
      const output = document.getElementById("output"); 
 
      // Hook to the ActiveItemChanged event and update the label 
      const updateActiveItem = () => { 
         const index = viewer.items.indexOf(viewer.activeItem); 
         output.innerHTML = "Active item index: " + index; 
      } 
      viewer.activeItemChanged.add(updateActiveItem); 
      updateActiveItem(); 
   } 
} 
export class ImageViewer_Example { 
   // LEADTOOLS ImageViewer to be used with this example 
   protected imageViewer: lt.Controls.ImageViewer = null; 
   // Generic state value used by the examples 
   public timesClicked: number = 0; 
 
   constructor(callback?: (viewer: lt.Controls.ImageViewer) => void) { 
      // Set the LEADTOOLS license. Replace this with your actual license file 
      lt.RasterSupport.setLicenseUri("https://demo.leadtools.com/licenses/v200/LEADTOOLSEVAL.txt", "EVAL", null); 
 
      // Create an image viewer inside the imageViewerDiv element 
      const imageViewerDiv = document.getElementById("imageViewerDiv"); 
      const createOptions: lt.Controls.ImageViewerCreateOptions = new lt.Controls.ImageViewerCreateOptions(imageViewerDiv); 
      this.imageViewer = new lt.Controls.ImageViewer(createOptions); 
      this.imageViewer.viewVerticalAlignment = lt.Controls.ControlAlignment.center; 
      this.imageViewer.viewHorizontalAlignment = lt.Controls.ControlAlignment.center; 
      this.imageViewer.autoCreateCanvas = true; 
 
      // Add Pan/Zoom interactive mode 
      // Click and drag to pan, CTRL-Click and drag to zoom in and out 
      this.imageViewer.interactiveModes.add(new lt.Controls.ImageViewerPanZoomInteractiveMode()); 
 
      // Load an image 
      this.imageViewer.imageUrl = "https://demo.leadtools.com/images/jpeg/cannon.jpg"; 
 
      this.imageViewer.zoom(lt.Controls.ControlSizeMode.fit, .9, this.imageViewer.defaultZoomOrigin); 
 
      const exampleButton = document.getElementById("exampleButton"); 
      exampleButton.addEventListener("click", () => { 
         this.timesClicked++; 
         // Run the example 
         if (callback) 
            callback(this.imageViewer); 
      }); 
   } 
} 
import { ImageViewer_Example } from "../ImageViewer"; 
 
export class ImageViewer_ActiveItemChangedExample { 
   viewerExample; 
   constructor() { 
      this.viewerExample = new ImageViewer_Example(this.run); 
   } 
 
   run = (viewer) => { 
      // Clear all the images already the viewer 
      viewer.items.clear(); 
      // Use vertical view layout 
      viewer.viewLayout = new lt.Controls.ImageViewerVerticalViewLayout(); 
      // Make sure the item size is larger than the image size (thumbnails mode) 
      viewer.itemBorderThickness = 3; 
      // Change the active item background color 
      viewer.activeItemBorderColor = "forestgreen"; 
 
      // Add 4 items to the viewer 
      for (let page = 1; page <= 4; page++) { 
         const item = new lt.Controls.ImageViewerItem(); 
         const imageUrl = "https://demo.leadtools.com/images/png/ocr" + page.toString() + ".png"; 
         item.url = imageUrl; 
         viewer.items.add(item); 
      } 
 
      const panZoom = viewer.interactiveModes.findById(lt.Controls.ImageViewerInteractiveMode.panZoomModeId); 
      // Tell the mode to set the active item for us 
      panZoom.autoItemMode = lt.Controls.ImageViewerAutoItemMode.autoSetActive; 
 
      const output = document.getElementById("output"); 
 
      // Hook to the ActiveItemChanged event and update the label 
      const updateActiveItem = () => { 
         const index = viewer.items.indexOf(viewer.activeItem); 
         output.innerHTML = "Active item index: " + index; 
      } 
      viewer.activeItemChanged.add(updateActiveItem); 
      updateActiveItem(); 
   } 
} 
export class ImageViewer_Example { 
   // LEADTOOLS ImageViewer to be used with this example 
   imageViewer = null; 
   // Generic state value used by the examples 
   timesClicked = 0; 
 
   constructor(callback) { 
      // Set the LEADTOOLS license. Replace this with your actual license file 
      lt.RasterSupport.setLicenseUri("https://demo.leadtools.com/licenses/v200/LEADTOOLSEVAL.txt", "EVAL", null); 
 
      // Create an image viewer inside the imageViewerDiv element 
      const imageViewerDiv = document.getElementById("imageViewerDiv"); 
      const createOptions = new lt.Controls.ImageViewerCreateOptions(imageViewerDiv); 
      this.imageViewer = new lt.Controls.ImageViewer(createOptions); 
      this.imageViewer.viewVerticalAlignment = lt.Controls.ControlAlignment.center; 
      this.imageViewer.viewHorizontalAlignment = lt.Controls.ControlAlignment.center; 
      this.imageViewer.autoCreateCanvas = true; 
 
      // Add Pan/Zoom interactive mode 
      // Click and drag to pan, CTRL-Click and drag to zoom in and out 
      this.imageViewer.interactiveModes.add(new lt.Controls.ImageViewerPanZoomInteractiveMode()); 
 
      // Load an image 
      this.imageViewer.imageUrl = "https://demo.leadtools.com/images/jpeg/cannon.jpg"; 
 
      this.imageViewer.zoom(lt.Controls.ControlSizeMode.fit, .9, this.imageViewer.defaultZoomOrigin); 
 
      const exampleButton = document.getElementById("exampleButton"); 
      exampleButton.addEventListener("click", () => { 
         this.timesClicked++; 
         // Run the example 
         if (callback) 
            callback(this.imageViewer); 
      }); 
   } 
} 
<!doctype html> 
<html lang="en"> 
<title>Controls Example | ActiveItemChanged</title> 
 
<head> 
   <script src="https://code.jquery.com/jquery-2.2.4.min.js" 
      integrity="sha256-BbhdlvQf/xTY9gja0Dq3HiwQF8LaCRTXxZKRutelT44=" crossorigin="anonymous"></script> 
 
   <script src="../../LT/Leadtools.js"></script> 
   <script src="../../LT/Leadtools.Controls.js"></script> 
   <script src="../../LT/Leadtools.Annotations.Engine.js"></script> 
   <script src="../../LT/Leadtools.Annotations.Designers.js"></script> 
   <script src="../../LT/Leadtools.Annotations.Rendering.Javascript.js"></script> 
   <script src="../../LT/Leadtools.Annotations.Automation.js"></script> 
   <script src="../../LT/Leadtools.ImageProcessing.Main.js"></script> 
   <script src="../../LT/Leadtools.ImageProcessing.Color.js"></script> 
   <script src="../../LT/Leadtools.ImageProcessing.Core.js"></script> 
   <script src="../../LT/Leadtools.ImageProcessing.Effects.js"></script> 
   <script src="../../LT/Leadtools.Document.js"></script> 
   <script src="../../LT/Leadtools.Document.Viewer.js"></script> 
   <style> 
      body { 
         font-family: 'Segoe UI', sans-serif; 
      } 
 
      #imageViewerDiv { 
         border: 1px solid #888; 
         width: 500px; 
         height: 500px; 
         background-color: #eee; 
      } 
   </style> 
 
   <!-- All demo files are bundled and appended to the window --> 
   <script src="../../bundle.js" type="text/javascript"></script> 
</head> 
 
<body> 
   <p>Press and drag on the image to pan.</p> 
   <p>Hold down the control key and press and drag on the image or pinch with two fingers to zoom in and out.</p> 
   <div> 
      <button type="button" id="exampleButton">Run Example</button> 
   </div> 
   <div id="imageViewerDiv"></div> 
   <div id="output"></div> 
</body> 
 
<script> 
   window.onload = () => { 
      const example = new window.examples.ImageViewer.ActiveItemChanged(); 
 
   }; 
</script> 
</html> 

Requirements

Target Platforms

Help Version 20.0.2019.10.14
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Leadtools.Controls Assembly