java - 运行 JPanel 窗体

Question

我是java初学者。我在 java (NetBeans) 中创建了一个 JPanel 表单。然后，我定义了一些 Action ，例如数学计算。当我运行我的项目时，我没有收到任何错误，但在运行时我看不到 JPanel 表单。因为我没有在主类中定义 jform 。我如何在主类中定义 JPanel 表单以在运行时显示 JPanel 表单。

public class NewJPanel extends javax.swing.JPanel {


    public NewJPanel() {
        initComponents();
    }

    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        jLabel1 = new javax.swing.JLabel();
        jLabel2 = new javax.swing.JLabel();
        jLabel3 = new javax.swing.JLabel();
        jTextField1 = new javax.swing.JTextField();
        jTextField2 = new javax.swing.JTextField();
        jTextField3 = new javax.swing.JTextField();
        jButton1 = new javax.swing.JButton();
        jButton2 = new javax.swing.JButton();
        jButton3 = new javax.swing.JButton();
        jButton4 = new javax.swing.JButton();
        jButton5 = new javax.swing.JButton();

        jLabel1.setText("First Number:");

        jLabel2.setText("Second Number:");

        jLabel3.setText("Result:");

        jButton1.setText("Add");
        jButton1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton1ActionPerformed(evt);
            }
        });

        jButton2.setText("Subtract");
        jButton2.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton2ActionPerformed(evt);
            }
        });

        jButton3.setText("Multiply");
        jButton3.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton3ActionPerformed(evt);
            }
        });

        jButton4.setText("Divide");
        jButton4.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton4ActionPerformed(evt);
            }
        });

        jButton5.setText("Clear");
        jButton5.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton5ActionPerformed(evt);
            }
        });

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(this);
        this.setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(66, 66, 66)
                .addComponent(jButton1)
                .addGap(45, 45, 45)
                .addComponent(jButton2)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 69, Short.MAX_VALUE)
                .addComponent(jButton3)
                .addGap(27, 27, 27))
            .addGroup(layout.createSequentialGroup()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(layout.createSequentialGroup()
                        .addGap(39, 39, 39)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addComponent(jLabel1)
                            .addComponent(jLabel2)
                            .addComponent(jLabel3))
                        .addGap(88, 88, 88)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                            .addComponent(jTextField1, javax.swing.GroupLayout.DEFAULT_SIZE, 77, Short.MAX_VALUE)
                            .addComponent(jTextField2)
                            .addComponent(jTextField3)))
                    .addGroup(layout.createSequentialGroup()
                        .addGap(120, 120, 120)
                        .addComponent(jButton4)
                        .addGap(45, 45, 45)
                        .addComponent(jButton5)))
                .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(39, 39, 39)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel1)
                    .addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(18, 18, 18)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel2)
                    .addComponent(jTextField2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(18, 18, 18)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel3)
                    .addComponent(jTextField3, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(34, 34, 34)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jButton1)
                    .addComponent(jButton2)
                    .addComponent(jButton3))
                .addGap(18, 18, 18)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jButton4)
                    .addComponent(jButton5))
                .addContainerGap(67, Short.MAX_VALUE))
        );
    }// </editor-fold>                        

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        double num1, num2, result;
        num1 = Double.parseDouble(jTextField1.getText());
        num2 = Double.parseDouble(jTextField2.getText());
        result = num1 + num2;
        jTextField3.setText(String.valueOf(result));
    }                                        

    private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        double num1, num2, result;
        num1 = Double.parseDouble(jTextField1.getText());
        num2 = Double.parseDouble(jTextField2.getText());
        result = num1 - num2;
        jTextField3.setText(String.valueOf(result));
    }                                        

    private void jButton3ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        double num1,num2, result;
        num1 = Double.parseDouble(jTextField3.getText());
        num2 = Double.parseDouble(jTextField2.getText());
        result = num1*num2;
        jTextField3.setText(String.valueOf(result));
    }                                        

    private void jButton4ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        double num1, num2, result;
        num1 = Double.parseDouble(jTextField1.getText());
        num2 = Double.parseDouble(jTextField2.getText());
        result = num1 / num2;

    }                                        

    private void jButton5ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        jTextField1.setText("");
        jTextField2.setText("");
        jTextField3.setText("");
    }                                        


    // Variables declaration - do not modify                     
    private javax.swing.JButton jButton1;
    private javax.swing.JButton jButton2;
    private javax.swing.JButton jButton3;
    private javax.swing.JButton jButton4;
    private javax.swing.JButton jButton5;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JTextField jTextField1;
    private javax.swing.JTextField jTextField2;
    private javax.swing.JTextField jTextField3;
    // End of variables declaration                   
}

Answer 1

JPanel 不是像 JFrame 这样的顶级容器的可运行类，您需要一个 main 方法。您应该创建一个 JFrame 表单，而不是创建 JPanel 表单，该表单具有为您自动生成的 main 方法。看起来您正在使用 Netbeans GUI Builder。只需打开一个新的 JFrame 表单。您只需将 JPanel 表单添加到 JFrame 表单即可。

使用 NetBeans 设计 View ，您只需将 JPanel 表单拖放到 JFrame 表单，如 here 所示

还要明确指定项目的 Main 类，请参阅 here