Create A JTree The Easy Way Using Java
Posted by admin on
October 13, 2009
I forgot where I got this code but I am posting it here for others who may want to have an easy way to use a JTree. Rather than doing lines of codes for adding nodes, you can use this class (I call it EasyJTree) to add notes using String names. Here is the code.
public class EasyJTree extends JTree { //create map of names to node objects private HashMap namesToNodes = new HashMap(); public EasyJTree() { //create root of tree DefaultMutableTreeNode root = new DefaultMutableTreeNode(""); this.setModel(new DefaultTreeModel(root)); //add to map namesToNodes.put("root", root); } //get node object with name private DefaultMutableTreeNode getNode(String name) { //make lowercase //name = name.toLowerCase(); //get node from map DefaultMutableTreeNode node = (DefaultMutableTreeNode)(namesToNodes.get(name)); //if not defined if(node == null) { //create new node DefaultMutableTreeNode newNode = new DefaultMutableTreeNode(name); //add to map namesToNodes.put(name, newNode); //return new node return newNode; } else { //return old node return node; } } public void expandRoot() { //expand path to root expandPath(new TreePath(getNode("root"))); } //add first node to second node public void addNodeTo(String childNodeName, String parentNodeName) { //get two nodes DefaultMutableTreeNode parentNode = getNode(parentNodeName); DefaultMutableTreeNode childNode = getNode(childNodeName); //add child to parent at the end of child list ((DefaultTreeModel)getModel()).insertNodeInto(childNode, parentNode, parentNode.getChildCount()); } }
To use the EasyJTree class is pretty easy. Note that you must always supply the root node’s String value as “root”. Do not worry. The class’ root node is set to hidden by default but the code needs a root node so it can form the tree hierarchy properly.
EasyJTree tree = new EasyJTree(); tree.addNodeTo("Item1","root"); tree.addNodeTo("Sub Item 1","Item1"); tree.addNodeTo("Sub Item 2","Item1"); tree.addNodeTo("Item2","root"); tree.expandRoot();
tags: java, jtree
No Comments
Java: Get Leaf Node Index From Leaf Nodes In A JTree
Posted by admin on
October 10, 2009
I created this method to return the index of a leaf node from its leaf nodes in the JTree object. Using the TreePaths of the root and the leaf node to search for, the method loops through all the root’s contents until it encounters the leaf node equal to the one passed to the second parameter.
public static int getLeafIndex(TreePath tproot, TreePath tp) { int index = -1; DefaultMutableTreeNode dmtn_dummy = null; while (true) { if (dmtn_dummy == null) dmtn_dummy = (DefaultMutableTreeNode) tproot.getLastPathComponent(); else dmtn_dummy = dmtn_dummy.getNextNode(); if (dmtn_dummy != null) { if (dmtn_dummy.isLeaf()) { index++; if (new TreePath(dmtn_dummy.getPath()).equals(tp)) break; } } else break; } return index; }
tags: index, jtree, leaf, node
2 Comments
Java: Paging Leaf Nodes Of JTree
Posted by admin on
October 7, 2009
I made a method for a JTree object that will mimic paging features within its leaf nodes. If you have FIRST, NEXT, PREVIOUS and LAST buttons and you click say, NEXT, it will go to the next leaf node of the JTree. If the path to that leaf node is not expanded, it will expand it right away. This is useful in cases wherein you only want the navigation to affect leaf nodes.
The method has 2 parameters: first is the JTree object while the second will require you what kind of paging you want. Either the FIRST, NEXT, PREVIOUS and LAST leaf nodes of the JTree. Here is the code:
public final static int FIRST = 0, NEXT = 1, PREVIOUS = 2, LAST = 3; public static boolean expandPagingLeaf(JTree tree, int paging) { TreePath tp = null; DefaultMutableTreeNode dmtn_dummy = null, dmtn = null, dmtn_prev = null; if (paging == FIRST) tp = tree.getPathForRow(0); else tp = tree.getSelectionPath(); dmtn = (DefaultMutableTreeNode) tp.getLastPathComponent(); while (true) { if (dmtn_dummy == null) if (paging == PREVIOUS) dmtn_dummy = dmtn.getPreviousNode(); else dmtn_dummy = dmtn.getNextNode(); else if (paging == PREVIOUS) dmtn_dummy = dmtn_dummy.getPreviousNode(); else dmtn_dummy = dmtn_dummy.getNextNode(); if (dmtn_dummy != null) { if (dmtn_dummy.isLeaf()) { if (isSameTreePath(new TreePath(dmtn_dummy.getPath()), tree.getSelectionPath())) return false; else if (paging != LAST) { tree.setSelectionPath(new TreePath(dmtn_dummy.getPath())); break; } } dmtn_prev = dmtn_dummy; } else { if (paging == LAST && dmtn_prev != null) { tree.setSelectionPath(new TreePath(dmtn_prev.getPath())); break; } else return false; } } tree.scrollPathToVisible(tree.getSelectionPath()); return true; }
To call the method to go to the next leaf node available, you can do it like this:
JTreeTool.expandPagingLeaf(tree, JTreeTool.NEXT)
