JTree学习

import  java.awt.Dimension;
import  java.awt.Color;
import  javax.swing.JFrame;
import  javax.swing.JPanel;
import  javax.swing.JScrollPane;
import  javax.swing.JTree;
import  javax.swing.BoxLayout;
import  javax.swing.tree.TreePath;
import  javax.swing.tree.DefaultMutableTreeNode;
import  javax.swing.tree.DefaultTreeModel;
/*
JTree的构造函数:
JTree()
JTree(Hashtable value)
JTree(Object[] value)//只有这个构造函数可以创建多个根结点
JTree(TreeModel newModel)
JTree(TreeNode root)
JTree(TreeNode root, boolean asksAllowsChildren)
JTree(Vector value)

*/
public   class  JTreeDemo
{
  public   static   void  main (String[] args)
{


   // 构造函数：JTree()
  JTree example1  =   new  JTree();



 
   // 构造函数：JTree(Object[] value)
  Object[] letters =  { " a " ,  " b " ,  " c " ,  " d " ,  " e " };
  JTree example2  =   new  JTree (letters);




   // 构造函数：JTree(TreeNode root)(TreeNode空)
   // 用空结点创建树
  DefaultMutableTreeNode node1  =   new  DefaultMutableTreeNode(); // 定义树结点
  JTree example3  =   new  JTree (node1); // 用此树结点做参数调用 JTree的构造函数创建含有一个根结点的树




   // 构造函数：JTree(TreeNode root)(同上,只是TreeNode非空)
   // 用一个根结点创建树
  DefaultMutableTreeNode node2  =   new  DefaultMutableTreeNode( " Color " );
  JTree example4  =   new  JTree (node2); // 结点不可以颜色,默认为白面黑字
  example4.setBackground (Color.lightGray);




   // 构造函数：JTree(TreeNode root, boolean asksAllowsChildren)(同上,只是TreeNode又有不同)
   // 使用DefaultMutableTreeNode类先用一个根结点创建树，设置为可添加孩子结点,再添加孩子结点
  DefaultMutableTreeNode color  =   new  DefaultMutableTreeNode( " Color " ,  true );
  DefaultMutableTreeNode gray  =   new  DefaultMutableTreeNode ( " Gray " );
  color.add (gray);
  color.add ( new  DefaultMutableTreeNode ( " Red " ));
  gray.add ( new  DefaultMutableTreeNode ( " Lightgray " ));
  gray.add ( new  DefaultMutableTreeNode ( " Darkgray " ));
  color.add ( new  DefaultMutableTreeNode ( " Green " ));
  JTree example5  =   new  JTree (color);
 
 
 
 
   // 构造函数：JTree(TreeNode root)(同上,只是TreeNode非空)
   // 通过逐个添加结点创建树
  DefaultMutableTreeNode biology  =   new  DefaultMutableTreeNode ( " Biology " );
  DefaultMutableTreeNode animal  =   new  DefaultMutableTreeNode ( " Animal " );
  DefaultMutableTreeNode mammal  =   new  DefaultMutableTreeNode ( " Mammal " );
  DefaultMutableTreeNode horse  =   new  DefaultMutableTreeNode ( " Horse " );
  mammal.add (horse);
  animal.add (mammal);
  biology.add (animal);
  JTree example6  =   new  JTree (biology);
  horse.isLeaf();
  horse.isRoot();
 
 


   // 构造函数:JTree(TreeModel newModel)
   // 用DefaultMutableTreeNodel类定义一个结点再用这个结点做参数定义一个用DefaultTreeMode
   // 创建一个树的模型,再用JTree的构造函数创建一个树
 
  DefaultMutableTreeNode root  =   new  DefaultMutableTreeNode ( " Root1 " );
  DefaultMutableTreeNode child1  =   new  DefaultMutableTreeNode ( " Child1 " );
  DefaultMutableTreeNode child11  =   new  DefaultMutableTreeNode ( " Child11 " );
  DefaultMutableTreeNode child111  =   new  DefaultMutableTreeNode ( " Child111 " );
  root.add (child1); child1.add (child11); child11.add (child111);
 
 
 
  DefaultTreeModel model  =   new  DefaultTreeModel (root);
 
  JTree example7  =   new  JTree (model);



  JPanel panel  =   new  JPanel();
  panel.setLayout ( new  BoxLayout (panel, BoxLayout.X_AXIS));
  panel.setPreferredSize ( new  Dimension ( 700 ,  400 ));
  panel.add ( new  JScrollPane (example1)); // JTree必须放在JScrollPane上
  panel.add ( new  JScrollPane (example2));
  panel.add ( new  JScrollPane (example3));
  panel.add ( new  JScrollPane (example4));
  panel.add ( new  JScrollPane (example5));
  panel.add ( new  JScrollPane (example6));
  panel.add ( new  JScrollPane (example7));
 



  JFrame frame  =   new  JFrame ( " JTreeDemo " );
  frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
  frame.setContentPane (panel);
  frame.pack();
  frame.show();
}
}
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在实际开发过程中会经常使用JTree组件，平时会遇到这样或那样的问题，在此将偶得一点经验写下来，与大家共享，希望对大家有所帮助。

private JTree jtNetDevice;//数组件申明
private JScrollPane jspTree;//滚动面板申明


1、初始化
    DefaultMutableTreeNode rootNode = new DefaultMutableTreeNode("root");
    jtNetDevice = new JTree(rootNode);
    jtNetDevice.setAutoscrolls(true);
    getTreeSelectionModel().setSelectionMode(TreeSelectionModel.SINGLE_TREE_SELECTION);//设置单选模式
    jspTree = new JScrollPane();
    jspTree.getViewport().add(jtNetDevice, null);

2、三个经常使用的取值函数
  private DefaultTreeModel getTreeModel(){
    return (DefaultTreeModel)jtNetDevice.getModel();
  }

  private DefaultMutableTreeNode getRootNode(){
    return (DefaultMutableTreeNode)getTreeModel().getRoot();
  }
 
  private TreeSelectionModel getTreeSelectionModel(){
    return jtNetDevice.getSelectionModel();
  }


3、根据node得到path：
  TreePath visiblePath = new TreePath(getTreeModel().getPathToRoot(node));

4、根据Path展开到该节点
  jtNetDevice.makeVisible(visiblePath);

5、根据path设定该节点选定
  jtNetDevice.setSelectionPath(visiblePath);

6、选中节点的方法
  首先，根据节点得到树路径，其中chosen为需要选中的节点
  TreePath visiblePath = new TreePath( ( (DefaultTreeModel) jtNetDevice.getModel()).
                                        getPathToRoot(chosen));
  然后根据Path选中该节点
  jtNetDevice.setSelectionPath(visiblePath);

7、滚动到可见位置
  jtNetDevice.scrollPathToVisible(visiblePath);

8、给JTree添加右键弹出菜单
  void jtNetDevice_mouseReleased(MouseEvent e) {
    if (e.isPopupTrigger()) {
      jPopupMenu1.show(e.getComponent(), e.getX(), e.getY());//弹出右键菜单
    }
  }

9、关于JTree的展开
   // If expand is true, expands all nodes in the tree.
   // Otherwise, collapses all nodes in the tree.
   public void expandAll(JTree tree, boolean expand) {
       TreeNode root = (TreeNode)tree.getModel().getRoot();
  
       // Traverse tree from root
       expandAll(tree, new TreePath(root), expand);
   }
   private void expandAll(JTree tree, TreePath parent, boolean expand) {
       // Traverse children
       TreeNode node = (TreeNode)parent.getLastPathComponent();
       if (node.getChildCount() >= 0) {
           for (Enumeration e=node.children(); e.hasMoreElements(); ) {
               TreeNode n = (TreeNode)e.nextElement();
               TreePath path = parent.pathByAddingChild(n);
               expandAll(tree, path, expand);
           }
       }
  
       // Expansion or collapse must be done bottom-up
       if (expand) {
           tree.expandPath(parent);
       } else {
           tree.collapsePath(parent);
       }
   }


10、如何遍历JTree
   // 创建树
   JTree tree = new JTree();
  
   // 添加树节点......
  
   // 遍历所有节点
   visitAllNodes(tree);
  
   // 仅遍历展开的节点
   visitAllExpandedNodes(tree);
  
   // Traverse all nodes in tree
   public void visitAllNodes(JTree tree) {
       TreeNode root = (TreeNode)tree.getModel().getRoot();
       visitAllNodes(root);
   }
   public void visitAllNodes(TreeNode node) {
       // node is visited exactly once
       process(node);
  
       if (node.getChildCount() >= 0) {
           for (Enumeration e=node.children(); e.hasMoreElements(); ) {
               TreeNode n = (TreeNode)e.nextElement();
               visitAllNodes(n);
           }
       }
   }
  
   // Traverse all expanded nodes in tree
   public void visitAllExpandedNodes(JTree tree) {
       TreeNode root = (TreeNode)tree.getModel().getRoot();
       visitAllExpandedNodes(tree, new TreePath(root));
   }
   public void visitAllExpandedNodes(JTree tree, TreePath parent) {
       // Return if node is not expanded
       if (!tree.isVisible(parent)) {
           return;
       }
  
       // node is visible and is visited exactly once
       TreeNode node = (TreeNode)parent.getLastPathComponent();
       process(node);
  
       // Visit all children
       if (node.getChildCount() >= 0) {
           for (Enumeration e=node.children(); e.hasMoreElements(); ) {
               TreeNode n = (TreeNode)e.nextElement();
               TreePath path = parent.pathByAddingChild(n);
               visitAllExpandedNodes(tree, path);
           }
       }
   }