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POEclipse SWT - Java Programming Dilemma
 

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    <p>I am writing an Eclipse Plugin that opens a file and displays all the images contained within the file. This image display is part of a GUI application. Each image is rendered by associating it with an SWT Canvas widget. When I open the file I have all the information I need to determine the number of images I will have to display. I though it would make sense to create all the Canvas objects, one after another and store each Canvas object in some type of array like data structure. Every file I open with have a different number of images to display. I decided to use an <code>ArrayList</code>. </p> <p>I proceed as follows: I create a Canvas object for each image and store all of the Canvas objects in a <code>ArrayList</code>. Here's the problem: Each Canvas object has a <code>PaintListener</code> and <code>MouseListener</code> associated with it - for resizing and detecting if an image has been 'clicked.' I am creating all the Canvas objects in a 'for loop' - which includes assigning a <code>PaintListener</code> and <code>MouseListener</code> to each Canvas object, like so:</p> <p>`</p> <pre><code>// // Assume the following ArrayLists have been defined: // myCanvases, myImages, and myFrames // for (int i = 0; i &lt; numberOfImages; i++) { canvas = new Canvas(getMyComposite(), SWT.BORDER | SWT.NO_MERGE_PAINTS | SWT.NONE ); canvas.setLayoutData(getMyGridData()); . . . canvas.addPaintListener(new PaintListener() { public void paintControl(final PaintEvent event) { if (myImages.get(i) != null) { myImages.get(i).dispose(); event.gc.drawImage(mySceneImages.get(element), 0, 0); } } }); currentCanvas.addMouseListener(new MouseAdapter() { @Override public void mouseUp(MouseEvent event) { getVideo().setCurrentFrame(myFrames.get(i).getFrameNumber()); } }); canvas.setVisible(true); myCanvases.add(i, canvas); } // End for (int i = 0; i &lt; numberOfScenes; i++) </code></pre> <p>`</p> <p><strong>The Problem</strong>: The variable 'i' is used to determine which element to access in the different ArrayLists in the <code>PaintListener</code> and <code>MouseListener</code>. Note I am using 'i' for illustrative purposes here. I realize the variable 'i' defined in the 'for loop' cannot be used in the inner classes of the Listeners. Anyway...... When the Listeners receive an event, whatever variable I do use to attempt to access a specific element of an ArrayList <strong>contains it's present value, not the value when the Listeners were defined.</strong></p> <p>How can I get around this in Java? What I literally need is code in the definition of each Listener that essentially says equates to:</p> <p>`</p> <pre><code>myCanvases.get(7); // or whatever the for loop iteration is for that specific object); // Not myCanvases.get(i); // - which will contain the present value of i; </code></pre> <p>`</p> <p>when the Listener executes.</p> <p>Any ideas would be appreciated.</p> <p>Thanks.</p>
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