Java JApplet：按钮树问题
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【中文标题】Java JApplet：按钮树问题【英文标题】：Java JApplet: Button-Tree problem 【发布时间】：2011-11-12 15:37:24 【问题描述】：此小程序应采用存储在 menuTree 中的树并遵循基于它的菜单构造。
currentNode 存储小程序当前所在的菜单，它的每个子项都应显示为按钮。
单击按钮后，小程序应将您带到一个新菜单，表示单击的按钮。
我无法在单击另一个按钮时更改按钮。
我不确定这棵树的构造是否正确，因为它不是特别容易测试。
任何帮助将不胜感激。
谢谢。
import javax.swing.*;
import javax.swing.tree.*;
import java.awt.event.*;
import java.awt.*;
public class Menu extends JApplet implements ActionListener
private static final long serialVersionUID = 2142470002L;
private JTree menuTree;
private DefaultMutableTreeNode currentNode;
private JPanel buttonPanel;
public void init()
this.setSize(700, 550);
buttonPanel=new JPanel();
buttonPanel.setSize(300, 500);
this.add(buttonPanel);
/**
* will make node out of the first entry in the array, then make nodes out of subsequent entries
* and make them child nodes of the first one. The process is repeated recursively for entries that are arrays.
* this idea of tree declaration as well as the code from the method was lovingly
* stolen from: http://www.apl.jhu.edu/~hall/java/Swing-Tutorial/Swing-Tutorial-JTree.html
*/
Object [] menuNames = "ROOT",
new Object[] "Classic Chess",
new Object[] "Game",
"AI",
"Hotseat",
"Online"
,
"Challenges",
new Object[] "Practice",
"Situations",
"Coaching"
,
,
new Object[] "Fairy Chess",
new Object[] "Game",
"AI",
"Hotseat",
"Online"
,
"Challenges",
new Object[] "Practice",
"Situations",
"Coaching"
,
"Create Pieces"
;
currentNode=processHierarchy(menuNames);
menuTree = new JTree(currentNode);
initializeButtons(currentNode);
/**
* Clicking one of the buttons(which should be in the children of the currentNode), takes you to that node in the tree
* setting currentNode to that node and redoing buttons to represent its children.
*/
public void actionPerformed(ActionEvent ae)
Button b=(Button)ae.getSource();
for(int i =0; i<currentNode.getChildCount(); i++)
if(b.getLabel().equals(currentNode.getChildAt(i)+""))
currentNode=(DefaultMutableTreeNode)currentNode.getChildAt(i);
initializeButtons(currentNode);
/**
* will make node out of the first entry in the array, then make nodes out of subsequent entries
* and make them child nodes of the first one. The process is repeated recursively for entries that are arrays.
* this idea of tree declaration as well as the code from the method was lovingly
* stolen from: http://www.apl.jhu.edu/~hall/java/Swing-Tutorial/Swing-Tutorial-JTree.html
*/
private DefaultMutableTreeNode processHierarchy(Object[] hierarchy)
DefaultMutableTreeNode node = new DefaultMutableTreeNode(hierarchy[0]);
DefaultMutableTreeNode child;
for (int i = 1; i < hierarchy.length; i++)
Object nodeSpecifier = hierarchy[i];
if (nodeSpecifier instanceof Object[]) // Ie node with children
child = processHierarchy((Object[]) nodeSpecifier);
else
child = new DefaultMutableTreeNode(nodeSpecifier); // Ie Leaf
node.add(child);
return (node);
/**
* creates buttons for each child of the given node, labels them with their String value, and adds them to the panel.
*/
private void initializeButtons(DefaultMutableTreeNode node)
Button b;
buttonPanel.removeAll();
for(int i =0; i<node.getChildCount(); i++)
b=new Button();
b.setLabel(""+node.getChildAt(i));
buttonPanel.add(b);
【问题讨论】：
Swing GUI 对象应构造为on the event dispatch thread。 “它不是特别容易测试。” ..menuTree = new JTree(currentNode); menuTree.setVisibleRowCount(6); JOptionPane.showMessageDialog(null, new JScrollPane(menuTree)); 2) 为什么这是一个小程序？ 3）如果不添加到小程序中，树是什么？ 4) 你打算给任何东西添加一个动作监听器吗？ 5）如果没有，为什么要实施？ 6) 小程序和面板都不应设置大小。 7) 你的问题是什么？
为sscce+1。
【参考方案1】：
按照@Andrew 的有用大纲，TreeSelectionListener 似乎很合适。有关详细信息，请参阅How to Use Trees。应用程序似乎更容易调试。使用revalidate() 是更新布局的关键。
import java.awt.BorderLayout;
import java.awt.Button;
import java.awt.Container;
import java.awt.EventQueue;
import java.awt.GridLayout;
import javax.swing.JApplet;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.event.TreeSelectionEvent;
import javax.swing.event.TreeSelectionListener;
import javax.swing.tree.DefaultMutableTreeNode;
/** @see http://***.com/questions/7342713 */
public class Menu extends JApplet
private JTree menuTree;
private JPanel buttonPanel;
public static void main(String[] args)
EventQueue.invokeLater(new Runnable()
@Override
public void run()
JFrame frame = new JFrame();
frame.setTitle("Menu");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
new Menu().initContainer(frame);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
);
@Override
public void init()
EventQueue.invokeLater(new Runnable()
@Override
public void run()
initContainer(Menu.this);
);
private void initContainer(Container container)
container.setLayout(new GridLayout(1, 0));
buttonPanel = new JPanel(new GridLayout(0, 1));
Object[] menuNames = "ROOT",
new Object[]"Classic Chess",
new Object[]"Game", "AI", "Hotseat", "Online",
"Challenges",
new Object[]"Practice", "Situations", "Coaching"
,
new Object[]"Fairy Chess",
new Object[]"Game", "AI", "Hotseat", "Online",
"Challenges",
new Object[]"Practice", "Situations", "Coaching",
"Create Pieces"
;
DefaultMutableTreeNode currentNode = processHierarchy(menuNames);
menuTree = new JTree(currentNode);
menuTree.setVisibleRowCount(10);
menuTree.expandRow(2);
initializeButtons(currentNode);
container.add(buttonPanel, BorderLayout.WEST);
container.add(new JScrollPane(menuTree), BorderLayout.EAST);
menuTree.addTreeSelectionListener(new TreeSelectionListener()
@Override
public void valueChanged(TreeSelectionEvent e)
initializeButtons((DefaultMutableTreeNode)
menuTree.getLastSelectedPathComponent());
);
private DefaultMutableTreeNode processHierarchy(Object[] hierarchy)
DefaultMutableTreeNode node = new DefaultMutableTreeNode(hierarchy[0]);
DefaultMutableTreeNode child;
for (int i = 1; i < hierarchy.length; i++)
Object nodeSpecifier = hierarchy[i];
if (nodeSpecifier instanceof Object[])
child = processHierarchy((Object[]) nodeSpecifier);
else
child = new DefaultMutableTreeNode(nodeSpecifier);
node.add(child);
return (node);
private void initializeButtons(DefaultMutableTreeNode node)
Button b;
buttonPanel.removeAll();
for (int i = 0; i < node.getChildCount(); i++)
b = new Button();
b.setLabel("" + node.getChildAt(i));
buttonPanel.add(b);
buttonPanel.revalidate();
【讨论】：
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