Java JTree仅展开一级节点
Java JTree仅展开一级节点
提问于 2009-02-04 09:10:58
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？
回答 5
Stack Overflow用户
回答已采纳
发布于 2009-02-04 09:46:43
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);Stack Overflow用户
发布于 2009-02-04 09:38:02
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。
Stack Overflow用户
发布于 2009-02-04 09:54:40
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();
}
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/510610
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