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Snippet to reproduce exception when calling getExpandedTreePaths()
This snippet shows how to cause an AssertionFailedException when calling getExpandedTreePaths() on a virtual tree. When clicking the "refresh" button for the first time, everything works fine. On the second time, the following error is logged: > !MESSAGE Invalid index value 2 >= 2 On the third time, an AssertionFailedException is thrown. See: #2491
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‎examples/org.eclipse.jface.snippets/Eclipse JFace Snippets/org/eclipse/jface/snippets/viewers/Snippet070VirtualViewerWithExpandedState.java‎

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/*******************************************************************************
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* Copyright (c) 2024 DSA GmbH and others.
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*
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* This program and the accompanying materials
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* are made available under the terms of the Eclipse Public License 2.0
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* which accompanies this distribution, and is available at
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* https://www.eclipse.org/legal/epl-2.0/
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*
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* SPDX-License-Identifier: EPL-2.0
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*
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* Contributors:
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* DSA GmbH - initial API and implementation
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*******************************************************************************/
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package org.eclipse.jface.snippets.viewers;
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import java.net.MalformedURLException;
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import java.net.URI;
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import org.eclipse.core.runtime.Platform;
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import org.eclipse.jface.resource.ImageDescriptor;
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import org.eclipse.jface.resource.JFaceResources;
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import org.eclipse.jface.resource.ResourceManager;
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import org.eclipse.jface.viewers.ColumnLabelProvider;
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import org.eclipse.jface.viewers.ILazyTreeContentProvider;
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import org.eclipse.jface.viewers.TreeNode;
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import org.eclipse.jface.viewers.TreePath;
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import org.eclipse.jface.viewers.TreeViewer;
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import org.eclipse.swt.SWT;
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import org.eclipse.swt.events.SelectionListener;
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import org.eclipse.swt.graphics.Image;
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import org.eclipse.swt.layout.BorderData;
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import org.eclipse.swt.layout.BorderLayout;
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import org.eclipse.swt.widgets.Shell;
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import org.eclipse.swt.widgets.ToolBar;
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import org.eclipse.swt.widgets.ToolItem;
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/**
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* A simple example to illustrate how to preserve the expand/collapse state when
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* using a virtual viewer.
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*/
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public class Snippet070VirtualViewerWithExpandedState {
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public static class SimpleNode extends TreeNode {
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public SimpleNode(Object value) {
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super(value);
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}
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public int getChildCount() {
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SimpleNode[] children = getChildren();
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return children == null ? 0 : children.length;
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}
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public void setParentChildren(SimpleNode... children) {
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for (TreeNode child : children) {
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child.setParent(this);
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}
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setChildren(children);
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}
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@Override
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public SimpleNode[] getChildren() {
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return (SimpleNode[]) super.getChildren();
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}
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@Override
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public String toString() {
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return "[%s], %s".formatted(getClass().getSimpleName(), getValue());
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}
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}
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public static class LazyContentProvider implements ILazyTreeContentProvider {
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private final TreeViewer viewer;
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public LazyContentProvider(TreeViewer viewer) {
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this.viewer = viewer;
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}
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@Override
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public void updateElement(Object parent, int index) {
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SimpleNode[] children = ((SimpleNode) parent).getChildren();
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if (children == null) {
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// viewer.setHasChildren(parent, false);
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} else if (children.length > index) {
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SimpleNode child = children[index];
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viewer.replace(parent, index, child);
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viewer.setChildCount(child, child.getChildCount());
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} else {
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Platform.getLog(getClass()).warn("Invalid index value %d >= %d".formatted(index, children.length));
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}
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}
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@Override
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public void updateChildCount(Object element, int currentChildCount) {
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int newChildCount = ((SimpleNode) element).getChildCount();
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if (currentChildCount != newChildCount) {
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viewer.setChildCount(element, newChildCount);
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}
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}
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@Override
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public Object getParent(Object element) {
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return ((SimpleNode) element).getParent();
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}
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}
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static SimpleNode root;
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static SimpleNode node0;
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static SimpleNode node1;
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static SimpleNode node2;
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static SimpleNode node3;
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static SimpleNode node4;
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static SimpleNode node5;
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static SimpleNode node6;
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static SimpleNode node7;
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static SimpleNode node8;
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public static boolean flip = false;
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public static void flip() {
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flip = !flip;
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if (flip) {
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node0.setParentChildren(node1, node2, node8);
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} else {
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node0.setParentChildren(node2, node8);
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}
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}
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public static void main(String[] args) throws MalformedURLException {
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root = new SimpleNode("Invisible");
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node0 = new SimpleNode(0);
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node1 = new SimpleNode(1);
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node2 = new SimpleNode(2);
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node3 = new SimpleNode(3);
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node4 = new SimpleNode(4);
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node5 = new SimpleNode(5);
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node6 = new SimpleNode(6);
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node7 = new SimpleNode(7);
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node8 = new SimpleNode(8);
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root.setParentChildren(node0);
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node0.setParentChildren(node2, node8);
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node2.setParentChildren(node3, node4, node5);
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node5.setParentChildren(node6, node7);
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Shell shell = new Shell();
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shell.setSize(500, 155);
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shell.setLayout(new BorderLayout());
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TreeViewer viewer = new TreeViewer(shell, SWT.MULTI | SWT.H_SCROLL | SWT.V_SCROLL | SWT.BORDER | SWT.VIRTUAL);
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viewer.setContentProvider(new LazyContentProvider(viewer));
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viewer.setLabelProvider(new ColumnLabelProvider());
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viewer.getTree().setLayoutData(new BorderData(SWT.CENTER));
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viewer.setUseHashlookup(true);
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viewer.setInput(root);
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viewer.expandAll();
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ToolBar toolBar = new ToolBar(shell, SWT.NONE);
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toolBar.setLayoutData(new BorderData(SWT.TOP));
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ResourceManager resourceManager = JFaceResources.managerFor(shell);
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ImageDescriptor imageDescriptor = ImageDescriptor
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.createFromURL(URI.create("platform:/plugin/org.eclipse.pde.ui/icons/elcl16/refresh.png").toURL());
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Image image = resourceManager.create(imageDescriptor);
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ToolItem toolItem = new ToolItem(toolBar, SWT.PUSH);
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toolItem.setImage(image);
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toolItem.addSelectionListener(SelectionListener.widgetSelectedAdapter(event -> {
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flip();
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TreePath[] treePaths = viewer.getExpandedTreePaths();
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viewer.setInput(root);
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viewer.setExpandedTreePaths(treePaths);
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// This refresh is important, as it recalculates all tree items. Because the
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// viewer doesn't fit in the shell, some of those items remain virtual, which
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// then cause an exception, the next time this listener is executed.
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viewer.refresh();
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}));
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shell.open();
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while (!shell.isDisposed()) {
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shell.getDisplay().readAndDispatch();
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}
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}
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}

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