为什么在运行此JFrame时我的按钮不出现？

Question

I am trying to make a Rock, Paper, Scissors game and I have added 3 buttons to the frame, however when I launch the program two of the buttons don't appear until you hover over them, anyone have any idea why?

import javax.swing.*;
import java.awt.event.*;
import java.util.Random;
import java.awt.FlowLayout;
import javax.swing.JOptionPane;
public class RPSFrame extends JFrame {
public static void main(String [] args){
    new RPSFrame();
}
public RPSFrame(){
    JFrame Frame1 = new JFrame();
    this.setSize(500,500);
    this.setVisible(true);
    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    this.setTitle("Rock, Paper or Scissors game");
    this.setLocationRelativeTo(null);
    ClickListener cl1 = new ClickListener();
    ClickListener cl2 = new ClickListener();
    ClickListener cl3 = new ClickListener();

    JPanel panel1 = new JPanel();
    JLabel label1 = new JLabel("Result:");
    panel1.setLayout(new FlowLayout(FlowLayout.CENTER, 25, 25));
    this.add(panel1);
    this.setVisible(false);

    JPanel panel2 = new JPanel();
    JButton Rock = new JButton("Rock");
    Rock.addActionListener(cl1);
    panel2.setLayout(new FlowLayout(FlowLayout.LEFT));
    panel2.add(Rock);
    this.add(panel2);
    this.setVisible(true);
    JPanel panel3 = new JPanel();
    JButton Paper = new JButton("Paper");
    Paper.addActionListener(cl2);
    panel3.setLayout(new FlowLayout(FlowLayout.CENTER));
    panel3.add(Paper);
    this.add(panel3);
    this.setVisible(true);
    JPanel panel4 = new JPanel();
    JButton Scissors = new JButton("Scissors");
    Scissors.addActionListener(cl3);
    panel4.setLayout(new FlowLayout(FlowLayout.RIGHT));
    panel4.add(Scissors);
    this.add(panel4);
    this.setVisible(true);
}
private class ClickListener implements ActionListener{

    public void actionPerformed(ActionEvent e){
        if(e.getSource() == "Rock"){
            int AI = new Random().nextInt(3) + 1;
            JOptionPane.showMessageDialog(null, "I have been clicked!");
        }
    }
}

}

Answer 1

The setVisible(true) statement should be invoked AFTER all the components have been added to the frame.

You currently have two setVisible(...) statements, so you need to get rid of the first one.

Edit:

1. Took a second look at the code. You have multiple setVisible(...) statements. Get rid of them all except for the last one.

2. Don't create separate panels for each button. Instead you create one panel (called buttonPanel ) for all the buttons. In your case you might use a horizontal BoxLayout . Add a button to the panel, then add glue then add a button, then add glue and then add your final button. Then add this buttonPanel to the NORTH of the frame. ie. this.add(buttonPanel, BorderLayout.NORTH) . Read the section from the Swing tutorial on How to Use Box Layout for more information on how the layout works and on what glue is.

Answer 2

The problem is that JFrame has a default BorderLayout . When you just add(component) without specifying a BorderLayout.[POSITION] eg add(panel, BorderLayout.SOUTH) , then the component will get added to the CENTER . The problem with that is each POSITION can only have one component. So the only component you see id the last one you add.

Now I don't know after specifying the positions, if you will get your desired result. A BorderLayout may not be the right fit. But just to see a change, you can set the layout to GridLayout(0, 1) and you will see the component.

this.setLayout(new GridLayout(0, 1));

If this is not the result you want, then you should look over Laying out Components within a Container to learn the different layouts available to you.

---

Also as I pointed out in my comment

if(e.getSource() == "Rock"){

with the above, you are trying to compare an object (ultimately a button) with a String. Instead you will want to compare the actionCommand

String command = e.getActionCommand();
if("Rock".equals(command)){