Java JApplet : Button-Tree problem

Question

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，代表单击的按钮。

我无法让按钮在单击另一个按钮时发生变化。

我不是特别确定这棵树是否构建正确，因为它不是特别容易测试。

如有任何帮助，我们将不胜感激。

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);
        }
    }

}

Answer 1

按照@Andrew 的帮助大纲，TreeSelectionListener 似乎很合适。参见 How to Use Trees了解详情。应用程序似乎更容易调试。使用 revalidate() 是更新修改后的布局的关键。

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://stackoverflow.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();
        }
    }
}