左边是JTree，右边是JTable，用于显示表格（头痛的有关问题，求解.）

左边是JTree，右边是JTable，用于显示表格（头痛的问题，求解...）
import java.awt.*;
import javax.swing.*;
import javax.swing.tree.*;
import javax.swing.event.*;
public class TestTree extends JFrame implements TreeSelectionListener{
  JPanel panel = new JPanel();
   
  JScrollPane scrollpane1,scrollpane2,scrollpane3; 
  JTable jt1,jt2; 
  JTree jtree;
  JSplitPane js;
  Object colName[]={"学号","姓名","年龄","家庭住址"};
  Object rowData[][]={{"2081714101","张三","20","湖北"},{"2081714102","王五","21","湖南"}};
  Object rowData1[][]={{"2091714101","李四","20","河南"},{"2091714102","王五","21","湖南"}};
 
  DefaultMutableTreeNode root = new DefaultMutableTreeNode("信息工程系"),
  jike = new DefaultMutableTreeNode("计科"),
  guangxin= new DefaultMutableTreeNode("光信"),
  jike1 = new DefaultMutableTreeNode("20817141"),
  jike2 = new DefaultMutableTreeNode("20917141");
   
  public TestTree() {
  setBounds(200,200,800,400);
  setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
  jike.add(jike1);
  jike.add(jike2);
  root.add(jike);
  root.add(guangxin);

  jtree = new JTree(root);
  jtree.addTreeSelectionListener(this);
  jtree.getSelectionModel().setSelectionMode(TreeSelectionModel.SINGLE_TREE_SELECTION);
  scrollpane1 = new JScrollPane(jtree);
  add(scrollpane1);
   
   
  jt1 =new JTable(rowData,colName);
  scrollpane2 = new JScrollPane(jt1);
  // panel.add(scrollpane2); 
  // add(panel);
   
  jt2 =new JTable(rowData1,colName);
  scrollpane3 = new JScrollPane(jt2);
// panel.add(scrollpane3); 
  // add(panel);
   
   
  js = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT,true,scrollpane1,panel);
  js.setDividerLocation(150);
  js.setOneTouchExpandable(true);
  add(js);
  setVisible(true);
  setContentPane(js);
  }
  public void valueChanged(TreeSelectionEvent e){
  JTree tree = (JTree) e.getSource();
  DefaultMutableTreeNode selectionNode =(DefaultMutableTreeNode)tree.getLastSelectedPathComponent();
  if (selectionNode==jike1){
  System.out.println("hello....");
  panel.add(scrollpane2); 
  add(panel);
  }  
  else if (selectionNode==jike2){
System.out.println("hello world....");
panel.add(scrollpane3); 
  add(panel);
  }


  }

  public static void main(String[] args){
  new TestTree();
  }
   
}

出现异常，而且显示的有问题，中间的分割线跑到最右边....高手指教啊

hello....
Exception in thread "AWT-EventQueue-0" java.lang.IllegalArgumentException: cannot add to layout: unknown constraint: null
  at javax.swing.plaf.basic.BasicSplitPaneUI$BasicHorizontalLayoutManager.addLayoutComponent(BasicSplitPaneUI.java:1417)
  at javax.swing.plaf.basic.BasicSplitPaneUI$BasicHorizontalLayoutManager.addLayoutComponent(BasicSplitPaneUI.java:1518)

  at java.awt.Container.addImpl(Container.java:1074)
  at javax.swing.JSplitPane.addImpl(JSplitPane.java:1015)
  at java.awt.Container.add(Container.java:959)
  at javax.swing.JFrame.addImpl(JFrame.java:540)
  at java.awt.Container.add(Container.java:365)
  at TestTree.valueChanged(TestTree.java:62)
  at javax.swing.JTree.fireValueChanged(JTree.java:2820)
  at javax.swing.JTree$TreeSelectionRedirector.valueChanged(JTree.java:3191)
  at javax.swing.tree.DefaultTreeSelectionModel.fireValueChanged(DefaultTreeSelectionModel.java:629)
  at javax.swing.tree.DefaultTreeSelectionModel.notifyPathChange(DefaultTreeSelectionModel.java:1078)
  at javax.swing.tree.DefaultTreeSelectionModel.setSelectionPaths(DefaultTreeSelectionModel.java:287)
  at javax.swing.tree.DefaultTreeSelectionModel.setSelectionPath(DefaultTreeSelectionModel.java:170)
  at javax.swing.JTree.setSelectionPath(JTree.java:1598)
  at javax.swing.plaf.basic.BasicTreeUI.selectPathForEvent(BasicTreeUI.java:2311)
  at javax.swing.plaf.basic.BasicTreeUI$Handler.handleSelection(BasicTreeUI.java:3520)
  at javax.swing.plaf.basic.BasicTreeUI$Handler.mousePressed(BasicTreeUI.java:3459)
  at java.awt.Component.processMouseEvent(Component.java:6260)
  at javax.swing.JComponent.processMouseEvent(JComponent.java:3267)
  at java.awt.Component.processEvent(Component.java:6028)
  at java.awt.Container.processEvent(Container.java:2041)
  at java.awt.Component.dispatchEventImpl(Component.java:4630)
  at java.awt.Container.dispatchEventImpl(Container.java:2099)
  at java.awt.Component.dispatchEvent(Component.java:4460)
  at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4574)
  at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4235)
  at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4168)
  at java.awt.Container.dispatchEventImpl(Container.java:2085)
  at java.awt.Window.dispatchEventImpl(Window.java:2478)
  at java.awt.Component.dispatchEvent(Component.java:4460)
  at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
  at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
  at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
  at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
  at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
  at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
  at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
hello world....
hello....


[解决办法]
改了下，更新组件不能一直add
要用updateUI();

Java code

import java.awt.*; 
 import javax.swing.*; 
 import javax.swing.tree.*; 
 import javax.swing.event.*; 
 public class TestTree extends JFrame implements TreeSelectionListener{ 
 JPanel panel = new JPanel(); 
    
 JScrollPane scrollpane1,scrollpane2,scrollpane3;   
 JTable jt1,jt2;   
 JTree jtree; 
 JSplitPane js; 
 Object colName[]={"学号","姓名","年龄","家庭住址"}; 
 Object rowData[][]={{"2081714101","张三","20","湖北"},{"2081714102","王五","21","湖南"}}; 
 Object rowData1[][]={{"2091714101","李四","20","河南"},{"2091714102","王五","21","湖南"}}; 
  
 DefaultMutableTreeNode root = new DefaultMutableTreeNode("信息工程系"),  
 
 jike = new DefaultMutableTreeNode("计科"), 
 guangxin= new DefaultMutableTreeNode("光信"), 
 jike1 = new DefaultMutableTreeNode("20817141"), 
 jike2 = new DefaultMutableTreeNode("20917141"); 
    
 public TestTree() { 
 setBounds(200,200,800,400); 
 setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
  
 jike.add(jike1); 
 jike.add(jike2); 
 root.add(jike); 
 root.add(guangxin); 
  
 jtree = new JTree(root); 
 jtree.addTreeSelectionListener(this); 
 jtree.getSelectionModel().setSelectionMode(TreeSelectionModel.SINGLE_TREE_SELECTION); 
 scrollpane1 = new JScrollPane(jtree); 
 add(scrollpane1); 
    
    
 jt1 =new JTable(rowData,colName); 
 scrollpane2 = new JScrollPane(jt1); 
 // panel.add(scrollpane2);   
 // add(panel); 
    
 jt2 =new JTable(rowData1,colName); 
 scrollpane3 = new JScrollPane(jt2); 
 // panel.add(scrollpane3);   
 // add(panel); 
    
    
 js = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT,true,scrollpane1,panel); 
 js.setDividerLocation(150); 
 js.setOneTouchExpandable(true); 
 add(js); 
 setVisible(true); 
 setContentPane(js); 
 } 
  
 public void valueChanged(TreeSelectionEvent e){ 
 JTree tree = (JTree) e.getSource(); 
 DefaultMutableTreeNode selectionNode =(DefaultMutableTreeNode)tree.getLastSelectedPathComponent(); 
 if (selectionNode==jike1){ 
   System.out.println("hello...."); 
   panel.removeAll(); 
   panel.add(scrollpane2);   
   panel.updateUI(); 
 }    
 else if (selectionNode==jike2){ 
   System.out.println("hello world...."); 
   panel.removeAll(); 
   panel.add(scrollpane3); 
   panel.updateUI(); 
 } 
 } 
  
 public static void main(String[] args){ 
 new TestTree();  
 } 
 }

[解决办法]
panel.removeAll();
这句不是必要的，
但是为了减少程序的资源消耗，这是一个好的习惯
（在想更新成新的组件之前，先移除老的组件）

panel.updateUI();
这个就是在组件更新之后，让组件按照当前的状态进行重绘
（如果没有这个，那即使你更新了组件（add，remove），组件的界面还是不会更新）

楼主可以看看java的API，这样对提高很有帮助
[解决办法]

探讨

add(panel);
请问为什么不用这句呢？panel没有添加到窗体。。。。

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