运行 JPanel 表单

Question

我是Java的初学者。我在java(NetBeans)中创建了一个JPanel表单。然后，我定义了一些动作，例如数学计算。当我运行我的项目时，我没有收到任何错误，但我在运行时看不到JPanel表单。因为我没有在主类中定义 jform。 如何在主类中定义JPanel窗体以在运行时向我显示JPanel窗体。

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

如果没有像JFrame这样的顶级容器，JPanel就不是一个可运行的类，你需要一个main方法。您应该创建一个JFrame窗体，而不是创建JPanel窗体，该窗体具有自动生成的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 设计视图，您只需将JPanel窗体拖放到窗体JFrame

如下所示另外，要显式指定项目的 Main 类，请参阅此处

Answer 2

JFrame frameName = new JFrame();
frameName.setVisible(true);
//Now add your JPanel (JPanel yourJPanelName = new JPanel();)
frameName.add(yourJPanelName);

你可以使用 JFrame。