JFace - TreeViewer

1) TreeNode

/**
 * It's used by TreeViewer
 * TreeNode root = new TreeNode("Root");
 * treeViewer = new TreeViewer(container, SWT.BORDER);
 * treeViewer.setLabelProvider(new TreeLableProvider());
 * treeViewer.setContentProvider(new TreeContentProvider());
 * treeViewer.setInput(root);
 * 
 * The root node has no parent
 *
 * @author Louis
 */
public class TreeNode {
    //Root has no parent
    public TreeNode parent;

    public String name;
    public List<TreeNode> chidren = new ArrayList<TreeNode>();

    public TreeNode(String name) {
        this.name = name;
    }

    public TreeNode(String name, TreeNode parent) {
        this.name = name;
        this.parent = parent;

        if (parent != null)
            parent.chidren.add(this);
    }

    public TreeNode(String name, TreeNode parent, List<TreeNode> children) {
        this.name = name;
        this.parent = parent;
        this.chidren = children;

        if (parent != null)
            parent.chidren.add(this);
    }

    public void addChild(String childName) {
        new TreeNode(childName, this);
    }

    public TreeNode getParent() {
        return parent;
    }

    public void setParent(TreeNode parent) {
        this.parent = parent;
    }

    public void setChidren(List<TreeNode> chidren) {
        this.chidren = chidren;
    }

    public TreeNode getChildNode(String nodeName) {
        return getChild(this, nodeName);
    }

    public List<TreeNode> getChidren() {
        return chidren;
    }

    public TreeNode getChild(String nodeName) {
        for (TreeNode child : chidren) {
            if (child.name.equals(nodeName)) {
                return child;
            }
        }

        return null;
    }

    public TreeNode getChild(TreeNode parent, String nodeName) {
        for (TreeNode child : parent.chidren) {
            if (child.name.equals(nodeName)) {
                return child;
            }
        }

        return null;
    }

    public boolean hasChild() {
        return this.chidren.size() > 0;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String toString() {
        return name == null ? "" : name;
    }

    public int hashCode() {
        return (name == null) ? 0 : name.hashCode();
    }
}

2) TreeLableProvider, TreeContentProvider

public class TreeLableProvider extends LabelProvider {
    @Override
    public String getText(Object element) {
        if (element instanceof TreeNode)
            return ((TreeNode) element).name;
        else
            return super.getText(element);
    }
}

public class TreeContentProvider implements ITreeContentProvider {
    //1)
    public Object[] getElements(Object inputElement) {
        Object[] elements = null;
        if (inputElement instanceof TreeNode) {
            TreeNode c = (TreeNode) inputElement;
            elements = c.chidren.toArray();
        } else
            elements = new Object[0];

        return elements;
    }

    //2) If has children, show +, click it to expand node
    public boolean hasChildren(Object element) {
        boolean hasChildren = false;

        if (element instanceof TreeNode) {
            TreeNode c = (TreeNode) element;
            hasChildren = c.chidren.size() > 0;
        }

        return hasChildren;
    }

    //3) Click + to get children from this method
    public Object[] getChildren(Object parentElement) {
        Object[] children = null;

        if (parentElement instanceof TreeNode) {
            TreeNode c = (TreeNode) parentElement;
            children = c.chidren.toArray();
        } else
            children = new Object[0];

        return children;
    }

    public Object getParent(Object element) {
        return null;
    }

    public void dispose() {
    }

    public void inputChanged(Viewer viewer, Object oldInput, Object newInput) {
    }
}

3) Create TreeViewer

//Must has a hidden root node, it's invisible, as ancestor of all other nodes
private TreeNode root = new TreeNode("Root");

private void createTreeViewer(Composite container) {
    treeViewer = new TreeViewer(container, SWT.BORDER);
    treeViewer.setLabelProvider(new TreeLableProvider());
    treeViewer.setContentProvider(new TreeContentProvider());
    treeViewer.setInput(root);

    tree = treeViewer.getTree();
    tree.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));
}

4) Add init data

private void initData() {
    root.getChidren().clear();
    
    //Level 1 Node - China
    TreeNode china = new TreeNode("China", root);
        //Level 2 Node - Guangdong
        TreeNode guangDong = new TreeNode("Guang Dong", china);
            guangDong.addChild("Zhu Hai");
            guangDong.addChild("Shen Zhen");

        //Level 2 Node - Fujian
        TreeNode fuJian = new TreeNode("Fu Jian", china);
            fuJian.addChild("Xia Men");
            fuJian.addChild("San Ming");
            new TreeNode("Fu Zhou", fuJian);

    //Level 1 - US
    TreeNode us = new TreeNode("US", root);
        TreeNode newYork = new TreeNode("New York", us);
            newYork.addChild("Beacon");
            newYork.addChild("Glen Cove");
            new TreeNode("Rome", newYork);
        
        us.addChild("Los Angeles");
        new TreeNode("Pittsburgh", us);
}