问Java JTree仅展开一级节点
EN

Stack Overflow用户

提问于 2009-02-04 01:10:58

回答 5查看 26.1K关注 0票数 12

对于JTree，假设根节点是级别0，并且根节点下可能最多有5个级别，我如何轻松地展开所有级别1节点，以便所有级别1&2分支和叶子都可见，但级别3及以下不可见？

jtree

java

swing

回答 5

Stack Overflow用户

回答已采纳

发布于 2009-02-04 01:46:43

感谢你们的快速反应。然而，我现在找到了我正在寻找的简单解决方案。由于某种原因，我就是看不到JavaDocs中的DefaultMutableTreeNode.getLevel()！仅供参考，我现在要做的是：

DefaultMutableTreeNode currentNode = treeTop.getNextNode();
do {
    if (currentNode.getLevel() == 1) 
        myTree.expandPath(new TreePath(currentNode.getPath()));
    currentNode = currentNode.getNextNode();
} while (currentNode != null);

票数 21

Stack Overflow用户

发布于 2009-02-04 01:38:02

您可以使用一些Tree实用程序类来实现这一点：

像this one一样

public class SimpleNavigatorTreeUtil {

   /**
    * Expands/Collapse specified tree to a certain level.
    * 
    * @param tree jtree to expand to a certain level
    * @param level the level of expansion
    */
   public static void expandOrCollapsToLevel(JTree tree, TreePath treePath,int level,boolean expand) {
      try {
         expandOrCollapsePath(tree,treePath,level,0,expand);
      }catch(Exception e) {
e.printStackTrace();
         //do nothing
      }
   }

   public static void expandOrCollapsePath (JTree tree,TreePath treePath,int level,int currentLevel,boolean expand) {
//      System.err.println("Exp level "+currentLevel+", exp="+expand);
      if (expand && level<=currentLevel && level>0) return;

      TreeNode treeNode = ( TreeNode ) treePath.getLastPathComponent();
      TreeModel treeModel=tree.getModel();
      if ( treeModel.getChildCount(treeNode) >= 0 ) {
         for ( int i = 0; i < treeModel.getChildCount(treeNode); i++  ) {
            TreeNode n = ( TreeNode )treeModel.getChild(treeNode, i);
            TreePath path = treePath.pathByAddingChild( n );
            expandOrCollapsePath(tree,path,level,currentLevel+1,expand);
         }
         if (!expand && currentLevel<level) return;
      }      
      if (expand) {
         tree.expandPath( treePath );
//         System.err.println("Path expanded at level "+currentLevel+"-"+treePath);
      } else {
         tree.collapsePath(treePath);
//         System.err.println("Path collapsed at level "+currentLevel+"-"+treePath);
      }
   }


}

基本上，您需要探索子节点，直到满足您的条件(这里是深度级别)，然后展开所有节点。

票数 3

Stack Overflow用户

发布于 2009-02-04 01:54:40

以下方法适用于第一级子对象。要展开所有子对象，请将.children()替换为.breadthFirstEnumeration()

import javax.swing.*;
import javax.swing.tree.*;
import java.awt.BorderLayout;
import java.awt.event.*;
import java.util.*;

public class Tree {
    public static void main(String[] args) {
        JPanel panel = new JPanel(new BorderLayout());
        final JTree tree = new JTree();
        panel.add(new JScrollPane(tree));
        JButton btn = new JButton("Press Me");
        btn.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent ae) {
                for (Enumeration e = ((TreeNode)tree.getModel().getRoot()).children();e.hasMoreElements();) {
                    TreeNode tn = (TreeNode)e.nextElement();
                    tree.expandPath(new TreePath(((DefaultTreeModel)tree.getModel()).getPathToRoot(tn)));
                }
            }
        });
        panel.add(btn, BorderLayout.SOUTH);
        JFrame frame = new JFrame("");
        frame.getContentPane().add(panel);
        frame.setSize(300, 300);
        frame.setLocation(100, 100);
        frame.pack();
        frame.show();
    }
}