因此，诀窍是使用单个TreeModel，将树的SelectionModels 和两个自定义TreeCellRenderers 链接起来，并使用TreeExpansionListener能够确定展开/折叠的树并镜像结果的能力。
基本上，每棵树都共享相同的TreeModel和SelectionModel，这使得生活变得如此简单，因为它们都会响应对两个模型所做的更改。
展开/折叠有点困难，因为这需要通过 custom 来处理TreeExpansionListener，它会检测谁触发了事件，然后通知对面的树发生了变化。
接下来，我使用一个常见的“数据对象”，它包含有关应该由树的...显示的数据的基本信息。
最后，我使用两个不同TreeCellRenderer的 s 来渲染由TreeModel
import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.SimpleDateFormat;
import java.util.Date;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.event.TreeExpansionEvent;
import javax.swing.event.TreeExpansionListener;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeCellRenderer;
import javax.swing.tree.DefaultTreeModel;
import javax.swing.tree.MutableTreeNode;
import javax.swing.tree.TreePath;
public class DynamicTreeDemo extends JPanel implements ActionListener {
protected static final SimpleDateFormat SDF = new SimpleDateFormat("HH:mm:ss");
private int newNodeSuffix = 1;
private static String ADD_COMMAND = "add";
private static String REMOVE_COMMAND = "remove";
private static String CLEAR_COMMAND = "clear";
private DefaultMutableTreeNode rootNode;
private final DefaultTreeModel treeModel;
private JTree left;
private JTree right;
public DynamicTreeDemo() {
super(new BorderLayout());
rootNode = new DefaultMutableTreeNode("Root Node");
treeModel = new DefaultTreeModel(rootNode);
left = new JTree(treeModel);
left.setCellRenderer(new LeftTreeCellRenderer());
right = new JTree(treeModel);
right.setCellRenderer(new RightTreeCellRenderer());
MyExpansionListener expansionListener = new MyExpansionListener(left, right);
left.addTreeExpansionListener(expansionListener);
right.addTreeExpansionListener(expansionListener);
right.setSelectionModel(left.getSelectionModel());
populateModel();
JButton addButton = new JButton("Add");
addButton.setActionCommand(ADD_COMMAND);
addButton.addActionListener(this);
JButton removeButton = new JButton("Remove");
removeButton.setActionCommand(REMOVE_COMMAND);
removeButton.addActionListener(this);
JButton clearButton = new JButton("Clear");
clearButton.setActionCommand(CLEAR_COMMAND);
clearButton.addActionListener(this);
JPanel panel = new JPanel(new GridLayout(1, 2));
panel.add(new JScrollPane(left));
panel.add(new JScrollPane(right));
add(panel, BorderLayout.CENTER);
JPanel buttons = new JPanel(new GridLayout(0, 3));
buttons.add(addButton);
buttons.add(removeButton);
buttons.add(clearButton);
add(buttons, BorderLayout.SOUTH);
}
protected TreeData createNodeData() {
return new TreeData("New Node " + newNodeSuffix++, SDF.format(new Date()));
}
public void populateModel() {
String p1Name = "Parent 1";
String p2Name = "Parent 2";
DefaultMutableTreeNode p1, p2;
p1 = addObject(null, p1Name);
p2 = addObject(null, p2Name);
addObject(p1, createNodeData());
addObject(p1, createNodeData());
addObject(p2, createNodeData());
addObject(p2, createNodeData());
}
@Override
public void actionPerformed(ActionEvent e) {
String command = e.getActionCommand();
if (ADD_COMMAND.equals(command)) {
// Add button clicked
addObject(createNodeData());
} else if (REMOVE_COMMAND.equals(command)) {
// Remove button clicked
removeCurrentNode();
} else if (CLEAR_COMMAND.equals(command)) {
// Clear button clicked.
clear();
}
}
/**
* Create the GUI and show it. For thread safety, this method should be
* invoked from the event-dispatching thread.
*/
private static void createAndShowGUI() {
// Create and set up the window.
JFrame frame = new JFrame("DynamicTreeDemo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Create and set up the content pane.
DynamicTreeDemo newContentPane = new DynamicTreeDemo();
newContentPane.setOpaque(true); // content panes must be opaque
frame.setContentPane(newContentPane);
// Display the window.
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args) {
// Schedule a job for the event-dispatching thread:
// creating and showing this application's GUI.
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
/**
* Remove all nodes except the root node.
*/
public void clear() {
rootNode.removeAllChildren();
treeModel.reload();
}
/**
* Add child to the currently selected node.
*/
public DefaultMutableTreeNode addObject(Object child) {
DefaultMutableTreeNode parentNode = null;
TreePath parentPath = left.getSelectionPath();
if (parentPath == null) {
parentNode = rootNode;
} else {
parentNode = (DefaultMutableTreeNode) (parentPath.getLastPathComponent());
}
return addObject(parentNode, child, true);
}
public DefaultMutableTreeNode addObject(DefaultMutableTreeNode parent,
Object child) {
return addObject(parent, child, false);
}
public DefaultMutableTreeNode addObject(DefaultMutableTreeNode parent,
Object child, boolean shouldBeVisible) {
DefaultMutableTreeNode childNode = new DefaultMutableTreeNode(child);
if (parent == null) {
parent = rootNode;
}
// It is key to invoke this on the TreeModel, and NOT DefaultMutableTreeNode
treeModel.insertNodeInto(childNode, parent, parent.getChildCount());
// Make sure the user can see the lovely new node.
if (shouldBeVisible) {
left.scrollPathToVisible(new TreePath(childNode.getPath()));
right.scrollPathToVisible(new TreePath(childNode.getPath()));
}
return childNode;
}
/**
* Remove the currently selected node.
*/
public void removeCurrentNode() {
TreePath currentSelection = left.getSelectionPath();
if (currentSelection != null) {
DefaultMutableTreeNode currentNode = (DefaultMutableTreeNode) (currentSelection
.getLastPathComponent());
MutableTreeNode parent = (MutableTreeNode) (currentNode.getParent());
if (parent != null) {
treeModel.removeNodeFromParent(currentNode);
return;
}
}
}
public class TreeData {
private String left;
private String right;
public TreeData(String left, String right) {
this.left = left;
this.right = right;
}
public String getLeft() {
return left;
}
public String getRight() {
return right;
}
}
public class LeftTreeCellRenderer extends DefaultTreeCellRenderer {
@Override
public Component getTreeCellRendererComponent(JTree tree, Object value, boolean sel, boolean expanded, boolean leaf, int row, boolean hasFocus) {
if (value instanceof DefaultMutableTreeNode) {
DefaultMutableTreeNode node = (DefaultMutableTreeNode) value;
Object userData = node.getUserObject();
if (userData instanceof TreeData) {
value = ((TreeData) userData).getLeft();
}
}
return super.getTreeCellRendererComponent(tree, value, sel, expanded, leaf, row, hasFocus);
}
}
public class RightTreeCellRenderer extends DefaultTreeCellRenderer {
@Override
public Component getTreeCellRendererComponent(JTree tree, Object value, boolean sel, boolean expanded, boolean leaf, int row, boolean hasFocus) {
if (value instanceof DefaultMutableTreeNode) {
DefaultMutableTreeNode node = (DefaultMutableTreeNode) value;
Object userData = node.getUserObject();
if (userData instanceof TreeData) {
value = ((TreeData) userData).getRight();
}
}
return super.getTreeCellRendererComponent(tree, value, sel, expanded, leaf, row, hasFocus);
}
}
public class MyExpansionListener implements TreeExpansionListener {
private JTree left;
private JTree right;
public MyExpansionListener(JTree left, JTree right) {
this.left = left;
this.right = right;
}
@Override
public void treeExpanded(TreeExpansionEvent event) {
TreePath path = event.getPath();
if (event.getSource() == left) {
right.expandPath(path);
} else {
left.expandPath(path);
}
}
@Override
public void treeCollapsed(TreeExpansionEvent event) {
TreePath path = event.getPath();
if (event.getSource() == left) {
right.collapsePath(path);
} else {
left.collapsePath(path);
}
}
}
}
有关更多详细信息，请参阅如何使用树
