java - JButtons 没有出现在我的 JFrame 上

Question

我正在制作一个包含 GUI 的程序。出于某种原因，当我运行程序时，我创建的 JButton 对象没有显示在我的 JFrame 上。这是代码:

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class ReverseAStringMain extends JPanel {
private JButton enterButton, exitButton;
private JTextField textField;
private JPanel buttonPanel;
private JTextArea textArea;


public ReverseAStringMain(){
    JButton enterButton = new JButton("Enter");
    JButton exitButton = new JButton("Exit");
    enterButton.setPreferredSize(new Dimension(60,60));
    exitButton.setPreferredSize(new Dimension(60,60));

    ButtonListener listener = new ButtonListener();
    enterButton.addActionListener(listener);
    exitButton.addActionListener(listener);

    buttonPanel = new JPanel();
    buttonPanel.setPreferredSize(new Dimension(200,50));
    buttonPanel.setBackground(Color.black);
    buttonPanel.add(enterButton);
    buttonPanel.add(exitButton);


    textField = new JTextField();
    textField.setSize(200, 100);

    textArea = new JTextArea();
    textArea.add(textField);


    add(buttonPanel);
    add(textField);

}

//Creating a ButtonListener class that implements the ActionListener interface
private class ButtonListener implements ActionListener{
        @Override
        //Overriding the ActionPerformed method of ActionListener
        public void actionPerformed(ActionEvent action) {
            if(action.getSource()== enterButton)
                enterButton();
            if(action.getSource()== exitButton)
                System.exit(0);
        }
}       

private void enterButton() {
            // TODO Auto-generated method stub

}


public static void main (String[] args){
    JFrame frame = new JFrame("Raj's Reverse a String Program");
    frame.setBackground(Color.white);
    frame.setVisible(true);
    frame.setResizable(false);
    frame.setLocationRelativeTo(null);
    frame.setSize(new Dimension(600,600));
    //frame.pack();
    frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
    frame.getContentPane().add(new ReverseAStringMain());



}

}

如果我的代码有任何问题或改进，请告诉我!

Answer 1

您在 JFrame 可见后将其添加到 JFrame 中。您应该在 JFrame 可见之前将它们添加到 JFrame，或者在添加组件之后重新验证 JFrame。