JFrame没有显示Java中的JPanel和其他小部件

Question

这是我的代码，我还是Java GUI的新手（本周刚开始）。据我所知，你创建了一个JFrame，向其中添加JPanels，然后在这些面板上添加JRadioButton等小部件。

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
public class Binary extends JFrame{
private JLabel header;
private JTextField userInput1;
private JButton doIt;
private JButton clear;
private JRadioButton binary, decimal;
private JLabel number2;
private JFrame frame1;
private JPanel panel1;
private JPanel panel2;
public Binary(){
    super("Number Converter");
    frame1 = new JFrame("Binary to Decimal Converter");
    frame1.setLayout(new FlowLayout());
    frame1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame1.setSize(250,500);
    frame1.setVisible(true);
    panel1 = new JPanel();
    panel1.setSize(250, 450);
    frame1.add(panel1);
    header = new JLabel("1- Select the mode: ");
    panel1.add(header);
    panel2 = new JPanel();
    panel2.setSize(250, 25);
    panel2.setOpaque(true);
    panel2.setBackground(Color.GRAY);
    frame1.add(panel2);

    ButtonGroup choices= new ButtonGroup();
    binary = new JRadioButton("Binary to Decimal"); // add the first radiobutton binary to decimal
    choices.add(binary);
    decimal = new JRadioButton("Decimal to Binary"); // add the second radiobutton decimal to binary
    choices.add(decimal);
    this.add(binary); // adds both to the program
    this.add(decimal);
    userInput1 = new JTextField(20); // Adds a blank text field for user input
    frame1.add(userInput1);
    number2 = new JLabel("2- Enter some words then click Do It:"); 
    frame1.add(number2);
    doIt = new JButton("Do It"); // left button do it
    frame1.add(doIt);
    clear = new JButton("Clear"); // right button clear
    frame1.add(clear);
}
}

对于我在这里的代码，当我运行它时，只有一个Binary to Decimal Converter的帧，没有其他内容，我在这里做错了什么？

Answer 1

您正在制作JFrame的两个副本，一个显示在屏幕上，另一个添加组件。

public class Binary extends JFrame {
    //...    
    private JFrame frame1;
    //...
    public Binary() {
        super("Number Converter");
        frame1 = new JFrame("Binary to Decimal Converter");

与其从JFrame扩展，不如简单地创建一个实例并使用它。。。

import java.awt.Color;
import java.awt.FlowLayout;
import javax.swing.ButtonGroup;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JRadioButton;
import javax.swing.JTextField;
public class Binary {
    private JLabel header;
    private JTextField userInput1;
    private JButton doIt;
    private JButton clear;
    private JRadioButton binary, decimal;
    private JLabel number2;
    private JFrame frame1;
    private JPanel panel1;
    private JPanel panel2;
    public Binary() {
        frame1 = new JFrame("Binary to Decimal Converter");
        frame1.setLayout(new FlowLayout());
        frame1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        panel1 = new JPanel();
        panel1.setSize(250, 450);
        frame1.add(panel1);
        header = new JLabel("1- Select the mode: ");
        panel1.add(header);
        panel2 = new JPanel();
        panel2.setSize(250, 25);
        panel2.setOpaque(true);
        panel2.setBackground(Color.GRAY);
        frame1.add(panel2);
        ButtonGroup choices = new ButtonGroup();
        binary = new JRadioButton("Binary to Decimal"); // add the first radiobutton binary to decimal
        choices.add(binary);
        decimal = new JRadioButton("Decimal to Binary"); // add the second radiobutton decimal to binary
        choices.add(decimal);
        frame1.add(binary); // adds both to the program
        frame1.add(decimal);
        userInput1 = new JTextField(20); // Adds a blank text field for user input
        frame1.add(userInput1);
        number2 = new JLabel("2- Enter some words then click Do It:");
        frame1.add(number2);
        doIt = new JButton("Do It"); // left button do it
        frame1.add(doIt);
        clear = new JButton("Clear"); // right button clear
        frame1.add(clear);
        frame1.pack();
        frame1.setVisible(true);
    }
}