按钮在Jframe中不显示

Question

btn3在Netbeans中运行时没有显示。当我在记事本中运行它时，它显示了第三个按钮。我实在想不出是什么问题。

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class Regform2 extends JFrame implements ActionListener {
    JLabel l1, l2, l3, l4, l5, l6, l7, l8;
    JTextField tf1, tf2, tf5, tf6, tf7;
    JButton btn1, btn2, btn3;
    JPasswordField p1, p2;
    Regform2() {
        setTitle("Registration Form in Java");
        l1 = new JLabel("Registration Form in Windows Form:");
        l1.setForeground(Color.blue);
        l1.setFont(new Font("Serif", Font.BOLD, 20));
        l2 = new JLabel("Name:");
        l3 = new JLabel("Email-ID:");
        l4 = new JLabel("Create Passowrd:");
        l5 = new JLabel("Confirm Password:");
        l6 = new JLabel("Country:");
        l7 = new JLabel("State:");
        l8 = new JLabel("Phone No:");
        tf1 = new JTextField();
        tf2 = new JTextField();
        p1 = new JPasswordField();
        p2 = new JPasswordField();
        tf5 = new JTextField();
        tf6 = new JTextField();
        tf7 = new JTextField();
        btn1 = new JButton("Submit");
        btn2 = new JButton("Clear");
        btn3 = new JButton("nxt");
        btn1.addActionListener(this);
        btn2.addActionListener(this);
        btn3.addActionListener(this);
        l1.setBounds(100, 30, 400, 30);
        l2.setBounds(80, 70, 200, 30);
        l3.setBounds(80, 110, 200, 30);
        l4.setBounds(80, 150, 200, 30);
        l5.setBounds(80, 190, 200, 30);
        l6.setBounds(80, 230, 200, 30);
        l7.setBounds(80, 270, 200, 30);
        l8.setBounds(80, 310, 200, 30);
        tf1.setBounds(300, 70, 200, 30);
        tf2.setBounds(300, 110, 200, 30);
        p1.setBounds(300, 150, 200, 30);
        p2.setBounds(300, 190, 200, 30);
        tf5.setBounds(300, 230, 200, 30);
        tf6.setBounds(300, 270, 200, 30);
        tf7.setBounds(300, 310, 200, 30);
        btn1.setBounds(50, 350, 100, 30);
        btn2.setBounds(170, 350, 100, 30);
        btn3.setBounds(300, 350, 100, 30);
        add(l1);
        add(l2);
        add(tf1);
        add(l3);
        add(tf2);
        add(l4);
        add(p1);
        add(l5);
        add(p2);
        add(l6);
        add(tf5);
        add(l7);
        add(tf6);
        add(l8);
        add(tf7);
        add(btn1);
        add(btn2);
        add(btn3);
        setVisible(true);
        setSize(700, 700);
        setLayout(null);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == btn1) {
            int x = 0;
            String s1 = tf1.getText();
            String s2 = tf2.getText();
            char[] s3 = p1.getPassword();
            char[] s4 = p2.getPassword();
            String s8 = new String(s3);
            String s9 = new String(s4);
            String s5 = tf5.getText();
            String s6 = tf6.getText();
            String s7 = tf7.getText();
            if (s8.equals(s9)) {
                JOptionPane.showMessageDialog(btn1, "Data Saved Successfully");
            } else {
                JOptionPane.showMessageDialog(btn1, "Password Does Not Match");
            }

        } else if (e.getSource() == btn2) {
            tf1.setText("");
            tf2.setText("");
            p1.setText("");
            p2.setText("");
            tf5.setText("");
            tf6.setText("");
            tf7.setText("");

        } else {
            this.dispose();
            NewJFrame nw = new NewJFrame();
            nw.setVisible(true);

        }
    }
    public static void main(String args[]) {
        new Regform2();
    }}

Answer 1

如果先设置setlayout(null)，然后设置setVisible(true)， btn3将在jframe中显示。这样的:

    setLayout(null);
    setVisible(true);
    setSize(700, 700);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

Answer 2

您需要添加一个JPanel。向这个面板添加组件。不要忘记在框架中添加面板，像这样:

    JPanel contentPane = new JPanel();
    content.add(new JButton("Test"));
    this.setDefaultCloseOperation(3);
    this.setContentPane(contentPanel);
    this.setSize(Width, Height);
    this.setResizable(false);
    this.setVisible(true);

Answer 3

此代码将工作…请在文件开头注明主框架代码构造函数，如 setTitle(); setSize(); setLayout();

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class Regform2 extends JFrame implements ActionListener {
JLabel l1, l2, l3, l4, l5, l6, l7, l8;
JTextField tf1, tf2, tf5, tf6, tf7;
JButton btn1, btn2, btn3;
JPasswordField p1, p2;
Regform2() {
    setTitle("Registration Form in Java");
    setSize(700, 700);
    setLayout(null);
    l1 = new JLabel("Registration Form in Windows Form:");
    l1.setForeground(Color.blue);
    l1.setFont(new Font("Serif", Font.BOLD, 20));
    l2 = new JLabel("Name:");
    l3 = new JLabel("Email-ID:");
    l4 = new JLabel("Create Passowrd:");
    l5 = new JLabel("Confirm Password:");
    l6 = new JLabel("Country:");
    l7 = new JLabel("State:");
    l8 = new JLabel("Phone No:");
    tf1 = new JTextField();
    tf2 = new JTextField();
    p1 = new JPasswordField();
    p2 = new JPasswordField();
    tf5 = new JTextField();
    tf6 = new JTextField();
    tf7 = new JTextField();
    btn1 = new JButton("Submit");
    btn2 = new JButton("Clear");
    btn3 = new JButton("Next");
    btn1.addActionListener(this);
    btn2.addActionListener(this);
    btn3.addActionListener(this);
    l1.setBounds(100, 30, 400, 30);
    l2.setBounds(80, 70, 200, 30);
    l3.setBounds(80, 110, 200, 30);
    l4.setBounds(80, 150, 200, 30);
    l5.setBounds(80, 190, 200, 30);
    l6.setBounds(80, 230, 200, 30);
    l7.setBounds(80, 270, 200, 30);
    l8.setBounds(80, 310, 200, 30);
    tf1.setBounds(300, 70, 200, 30);
    tf2.setBounds(300, 110, 200, 30);
    p1.setBounds(300, 150, 200, 30);
    p2.setBounds(300, 190, 200, 30);
    tf5.setBounds(300, 230, 200, 30);
    tf6.setBounds(300, 270, 200, 30);
    tf7.setBounds(300, 310, 200, 30);
    btn1.setBounds(50, 350, 100, 30);
    btn2.setBounds(170, 350, 100, 30);
    btn3.setBounds(290, 350, 100, 30);
    add(l1);
    add(l2);
    add(tf1);
    add(l3);
    add(tf2);
    add(l4);
    add(p1);
    add(l5);
    add(p2);
    add(l6);
    add(tf5);
    add(l7);
    add(tf6);
    add(l8);
    add(tf7);
    add(btn1);
    add(btn2);
    add(btn3);
    setVisible(true);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
public void actionPerformed(ActionEvent e) {
    if (e.getSource() == btn1) {
        int x = 0;
        String s1 = tf1.getText();
        String s2 = tf2.getText();
        char[] s3 = p1.getPassword();
        char[] s4 = p2.getPassword();
        String s8 = new String(s3);
        String s9 = new String(s4);
        String s5 = tf5.getText();
        String s6 = tf6.getText();
        String s7 = tf7.getText();
        if (s8.equals(s9)) {
            JOptionPane.showMessageDialog(btn1, "Data Saved Successfully");
        } else {
            JOptionPane.showMessageDialog(btn1, "Password Does Not Match");
        }

    } else if (e.getSource() == btn2) {
        tf1.setText("");
        tf2.setText("");
        p1.setText("");
        p2.setText("");
        tf5.setText("");
        tf6.setText("");
        tf7.setText("");

    } else {
        this.dispose();
        //NewJFrame nw = new NewJFrame();
        //nw.setVisible(true);

    }
}
public static void main(String args[]) {
    new Regform2();
}

}