java - 使用 swing 在运行时创建和显示对象

Question

我正在尝试为允许插入和删除的 BST 树创建一个简单的 GUI。但是，我在运行时将组件插入 GUI 时遇到了很多麻烦。我想做的是在每次发生插入或删除时“刷新”GUI。我创建了一个名为 printBst 的方法，它创建 Jlabels 来显示编号索引，如下所示，但它们没有显示出来。之后我尝试重新验证和验证 GUI，但它仍然不起作用。有人有什么想法吗？

package source;
import javax.swing.*;
import source.BST.BSTnode;

import java.awt.Color;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.util.ArrayList;
import java.util.List;

public class Frame2 extends JFrame implements  ActionListener{
    BST bst;
    JPanel displayPanel, buttonPanel, totalGUI;
    JButton insertButton, deleteButton, resetButton;
    JTextField insertField, deleteField;

    public JPanel createContentPane (){
        bst = new BST();
        totalGUI = new JPanel();
        totalGUI.setLayout(null);

        displayPanel = new JPanel();
        displayPanel.setLayout(null);
        displayPanel.setLocation(10, 80);
        displayPanel.setSize(400, 300);
        totalGUI.add(displayPanel);

        buttonPanel = new JPanel();
        buttonPanel.setLayout(null);
        buttonPanel.setLocation(10, 0);
        buttonPanel.setSize(800, 80);
        totalGUI.add(buttonPanel);

        insertField = new JTextField(1);
        insertField.addActionListener(this);
        insertField.setLocation(0, 10);
        insertField.setSize(150, 30);
        buttonPanel.add(insertField);

        insertButton = new JButton("Insert");
        insertButton.setLocation(160, 10);
        insertButton.setSize(150, 30);
        insertButton.addActionListener(this);
        buttonPanel.add(insertButton);

        deleteField = new JTextField(1);
        deleteField.addActionListener(this);
        deleteField.setLocation(320, 10);
        deleteField.setSize(150, 30);
        buttonPanel.add(deleteField);

        deleteButton = new JButton("Delete");
        deleteButton.setLocation(480, 10);
        deleteButton.setSize(150, 30);
        deleteButton.addActionListener(this);
        buttonPanel.add(deleteButton);

        resetButton = new JButton("Reset");
        resetButton.setLocation(640, 10);
        resetButton.setSize(150, 30);
        resetButton.addActionListener(this);
        buttonPanel.add(resetButton);

        totalGUI.setOpaque(true);
        return totalGUI;
    }

    public void printBst(BSTnode node, int x, int x2, int y) {
        if (node != null) {
            JLabel current = new JLabel(""+ node.data);
            current.setLocation((x+x2)/2, y);
            current.setSize(100, 30);
            current.setHorizontalAlignment(0);
            displayPanel.add(current);
            printBst(node.left, x, (x2+x)/2, y+60);
            printBst(node.right, (x2+x)/2, x2, y+60);
            System.out.println("here");
        }
    }

    public void actionPerformed(ActionEvent e) {
        if(e.getSource() == insertButton)
        {
            bst.insert(Integer.valueOf(insertField.getText()));
            displayPanel.removeAll();
            printBst(bst.root, 0, 800, 0);
            totalGUI.revalidate();  
            validate(); 
        }
        else if(e.getSource() == deleteButton)
        {
            bst.delete(Integer.valueOf(deleteField.getText()));
            displayPanel.removeAll();
            printBst(bst.root, 0, 800, 0);
            totalGUI.revalidate();  
            validate(); 
        }
        else if(e.getSource() == resetButton)
        {
            bst.clear();
            displayPanel.removeAll();
            printBst(bst.root, 0, 800, 0);
            totalGUI.revalidate();  
            validate(); 
        }
    }

    private static void createAndShowGUI() {

        JFrame.setDefaultLookAndFeelDecorated(true);
        JFrame frame = new JFrame("[=] JButton Scores! [=]");

        Frame2 demo = new Frame2();
        frame.setContentPane(demo.createContentPane());

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(900, 400);
        frame.setVisible(true);

    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
}

Answer 1

确保在从 displayPanel 移除组件后调用 revalidate() 和 repaint() 即:

displayPanel.removeAll();
printBst(0, 800, 0);
displayPanel.revalidate();
displayPanel.repaint();

另外，请注意:

printBst(0, 800, 0);

导致 displayPanel 内的无效(不在边界内)坐标，其大小定义为 (400, 300) 窗口的左上角为 0,0。尝试以下操作，您应该会在面板中间的某处看到您的标签:

printBst(0, 400, 0);

Absolute positioning可能很难管理。查看A Visual Guide to Layout Managers看看你是否能找到合适的布局来帮助你。

您还可以考虑可以为您提供 2D Canvas 的现成框架。例如JGraph , JFreeChart或 Piccolo2D .