创建 UI java 的问题

Question

我正在尝试用 java 制作一个扫雷游戏，但是当按下新游戏按钮时我的组件没有显示出来。这是整个代码：

    /*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package campominado;

import java.awt.BorderLayout;
import java.awt.FlowLayout;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;

/**
 *
 * @author Felipe
 */
public class MainUI extends javax.swing.JFrame {

    /**
     * Creates new form MainUI
     */
    public MainUI() {
        initComponents();
    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        jMenuBar1 = new javax.swing.JMenuBar();
        file = new javax.swing.JMenu();
        novoJogo = new javax.swing.JMenuItem();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        file.setText("File");

        novoJogo.setText("Novo Jogo");
        novoJogo.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                novoJogoActionPerformed(evt);
            }
        });
        file.add(novoJogo);

        jMenuBar1.add(file);

        setJMenuBar(jMenuBar1);

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 400, Short.MAX_VALUE)
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 277, Short.MAX_VALUE)
        );

        pack();
    }// </editor-fold>                        

    private void novoJogoActionPerformed(java.awt.event.ActionEvent evt) {                                         
        JPanel area = new JPanel();
        JPanel areaJogo = new JPanel();
        JPanel areaMenu = new JPanel();

        this.add(area);

        area.setLayout(new BorderLayout());
        area.add(areaMenu, BorderLayout.NORTH);
        area.add(areaJogo, BorderLayout.SOUTH);

        JLabel linhas, colunas, minas;
        linhas = new JLabel("Linhas:");
        colunas = new JLabel("Colunas:");
        minas = new JLabel("Minas:");
        JTextField lin, col, min;
        lin = new JTextField();
        col = new JTextField();
        min = new JTextField();

        areaMenu.setLayout(new FlowLayout());
        areaMenu.add(linhas);
        areaMenu.add(lin);
        areaMenu.add(colunas);
        areaMenu.add(col);
        areaMenu.add(minas);
        areaMenu.add(min);
        areaMenu.add(new JButton("Iniciar"));

        areaMenu.validate();
        areaMenu.repaint();
        System.out.println("teste");
    }                                        

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /* Set the Nimbus look and feel */
        //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
         * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
         */
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(MainUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(MainUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(MainUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(MainUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(() -> {
            new MainUI().setVisible(true);
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JMenu file;
    private javax.swing.JMenuBar jMenuBar1;
    private javax.swing.JMenuItem novoJogo;
    // End of variables declaration                   
}

关于一个相关问题：在此方法开始工作后，我计划使用网格布局上的许多按钮为 OK 按钮创建一个侦听器，以使用游戏的单元格填充第二个面板。有没有更好的方法可以做到这一点，或者我的想法很好？

Answer 1

当您在运行时将JPanel 添加到this 时，您必须指出this 的布局已更改，以便swing 可以重做新布局并重新绘制。
您的更改不仅限于 areaMenu。
所以而不是：

areaMenu.validate();
areaMenu.repaint();

呼叫：

this.revalidate();  // redo the layout and notify the parent 
this.repaint();     // redraw the updated state

详情请参阅here。