Not all of my JButtons are showing up after I add a dozen of them. What am I doing wrong?

问题

I want to add 52 buttons in a JPanel. All with ActionListeners. When I reach a certain amount (13) and run the program, not all of the buttons show up. For example I've added 15 buttons and only 9 or 12 of them show up. Sometimes all of them, but not every time.

Here's the code for two of the JButtons:

    JButton button_one=new JButton();
    button_one.setPreferredSize(new Dimension(100,150));
    mainpanel.add(button_one);
    button_one.addActionListener(new ActionListener(){
        
        @Override
        public void actionPerformed(ActionEvent button_1_picked){
            amount_of_cards_picked=amount_of_cards_picked+1;
            cardamountcheck();
            if(twocardspicked==true){
                userpick2=0;
                System.out.println(setoutcards[userpick2]);
                pairdetermination();
            }
            else if(twocardspicked==false){
                userpick1=0;
                System.out.println(setoutcards[userpick1]);
                
            }
        }
    });
    
    JButton button_two = new JButton();
    button_two.setPreferredSize(new Dimension(100, 150));
    mainpanel.add(button_two);
    button_two.addActionListener(new ActionListener(){
        
        @Override
        public void actionPerformed(ActionEvent button_2_picked){
            amount_of_cards_picked=amount_of_cards_picked+1;
            cardamountcheck();
            if(twocardspicked==true){
                userpick2=1;
                System.out.println(setoutcards[userpick2]);
                pairdetermination();
            }
            else if(twocardspicked==false){
                userpick1=1;
                System.out.println(setoutcards[userpick1]);
                
            }
        }
    });

Basically when one of these buttons are clicked, variables in my code get changed. These buttons run fine and work exactly how I want them to, but they don't all appear when there is more than 13 of them, and I need 52.

回答1:

I want to add 52 buttons in a JPanel. All with ActionListeners.

Done. I created a GUI that displays 52 JButtons. I made them half the size of the OP's, so the GUI would fit better in the answer.

It's fairly straightforward using a GridLayout on a JPanel.

Here's the complete runnable code. A minimal reproducible example.

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class FiftyTwoJButtonGUI implements Runnable {

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new FiftyTwoJButtonGUI());
    }

    @Override
    public void run() {
        JFrame frame = new JFrame("52 JButton GUI");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        
        frame.add(createMainPanel(), BorderLayout.CENTER);
        
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }
    
    private JPanel createMainPanel() {
        JPanel panel = new JPanel(new GridLayout(0, 13, 5, 5));
        panel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
        
        CardListener listener = new CardListener();
        
        for (int i = 0; i < 52; i++) {
            JButton button = new JButton("" + (i + 1));
            button.addActionListener(listener);
            button.setPreferredSize(new Dimension(50, 75));
            panel.add(button);
        }
        
        return panel;
    }
    
    public class CardListener implements ActionListener {

        @Override
        public void actionPerformed(ActionEvent event) {
            JButton button = (JButton) event.getSource();
            int cardNumber = Integer.valueOf(button.getText());
            System.out.println(cardNumber);
        }
        
    }

}

来源：https://stackoverflow.com/questions/65596037/not-all-of-my-jbuttons-are-showing-up-after-i-add-a-dozen-of-them-what-am-i-doi