org.csstudio.alarm.beast.ui.alarmtree.Snippet047VirtualLazyTreeViewer.java Source code

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Here is the source code for org.csstudio.alarm.beast.ui.alarmtree.Snippet047VirtualLazyTreeViewer.java

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/*******************************************************************************
 * Copyright (c) 2006, 2007 Tom Schindl and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     Tom Schindl - initial API and implementation
 *******************************************************************************/

package org.csstudio.alarm.beast.ui.alarmtree;

import org.eclipse.jface.viewers.ILazyTreeContentProvider;
import org.eclipse.jface.viewers.LabelProvider;
import org.eclipse.jface.viewers.TreeViewer;
import org.eclipse.jface.viewers.Viewer;
import org.eclipse.swt.SWT;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;

/**
 * A simple TreeViewer to demonstrate usage of an ILazyContentProvider.
 */
@SuppressWarnings("nls")
public class Snippet047VirtualLazyTreeViewer {
    // Totally beside the point but was confusing when
    // trying to understand this snippet:
    // The model is a hack, not an obvious tree.
    // The tree usually doesn't show its 'root' element.
    // Here elements[] is the input to the tree viewer,
    // but because getParent() returns elements[] as parent of elements[],
    // those elements[] in the input serve as both the (not visible) root
    // of the tree and the first (visible) level.

    private class MyContentProvider implements ILazyTreeContentProvider {
        private TreeViewer viewer;
        private IntermediateNode[] elements;

        public MyContentProvider(TreeViewer viewer) {
            this.viewer = viewer;
        }

        @Override
        public void dispose() {

        }

        @Override
        public void inputChanged(Viewer viewer, Object oldInput, Object newInput) {
            this.elements = (IntermediateNode[]) newInput;
        }

        @Override
        public Object getParent(Object element) {
            if (element instanceof LeafNode)
                return ((LeafNode) element).parent;
            return elements;
        }

        @Override
        public void updateElement(Object parent, int index) {
            Object element;
            if (parent instanceof IntermediateNode)
                element = ((IntermediateNode) parent).children[index];

            else
                element = elements[index];
            viewer.replace(parent, index, element);
            updateChildCount(element, -1);
        }

        @Override
        public void updateChildCount(Object element, int currentChildCount) {

            int length = 0;
            if (element instanceof IntermediateNode) {
                IntermediateNode node = (IntermediateNode) element;
                length = node.children.length;
            }
            if (element == elements)
                length = elements.length;
            viewer.setChildCount(element, length);
        }
    }

    public class LeafNode {
        public int counter;
        public IntermediateNode parent;

        public LeafNode(int counter, IntermediateNode parent) {
            this.counter = counter;
            this.parent = parent;
        }

        @Override
        public String toString() {
            return "Leaf " + this.counter;
        }
    }

    public class IntermediateNode {
        public int counter;
        public LeafNode[] children = new LeafNode[0];

        public IntermediateNode(int counter) {
            this.counter = counter;
        }

        @Override
        public String toString() {
            return "Node " + this.counter;
        }

        public void generateChildren(int i) {
            children = new LeafNode[i];
            for (int j = 0; j < i; j++) {
                children[j] = new LeafNode(j, this);
            }

        }
    }

    public Snippet047VirtualLazyTreeViewer(Shell shell) {
        // THIS IS THE KEY POINT:
        // With SWT.MULTI expanding tree items is slow as snot
        // (at least on Windows, Eclipse 3.6.2)
        // See https://bugs.eclipse.org/bugs/show_bug.cgi?id=259141
        // The original snippet without SWT.MULTI is fine.
        final TreeViewer v = new TreeViewer(shell, SWT.VIRTUAL | SWT.BORDER | SWT.MULTI);
        v.setLabelProvider(new LabelProvider());
        v.setContentProvider(new MyContentProvider(v));
        v.setUseHashlookup(true);
        IntermediateNode[] model = createModel();
        v.setInput(model);
        v.getTree().setItemCount(model.length);

    }

    private IntermediateNode[] createModel() {
        IntermediateNode[] elements = new IntermediateNode[10];

        for (int i = 0; i < 10; i++) {
            elements[i] = new IntermediateNode(i);
            elements[i].generateChildren(1000);
        }

        return elements;
    }

    /**
     * @param args
     */
    public static void main(String[] args) {
        Display display = new Display();
        Shell shell = new Shell(display);
        shell.setLayout(new FillLayout());
        new Snippet047VirtualLazyTreeViewer(shell);
        shell.open();

        while (!shell.isDisposed()) {
            if (!display.readAndDispatch())
                display.sleep();
        }

        display.dispose();

    }

}