鼠标悬停之前，JButton不会出现

Question

When i run my program everything works as planned except that the button i have to change the cards on the screen does not appear until it is moused over. Im assuming this is because whatever container that is holding the images is over it but i dont know how to move it into the background or even what kind of container i can use to add images to.

import java.io.*;
import java.awt.*;
import javax.swing.*;
import java.util.Random;
import java.awt.event.*;
import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;

public class oneplayer extends JFrame {
    BufferedImage  image1, image2, image3, image4;
    Random gen = new Random();
    public void redo() {
        int p1, p2, p3, p4;
        p1 = gen.nextInt(13) + 1;
        p2 = gen.nextInt(13) + 14;
        p3 = gen.nextInt(13) + 27;
        p4 = gen.nextInt(13) + 40;
         try {
         File input1 = new File("C:/Users/Mike/Desktop/eclipse/workspace/inClass/src/" + p1 + ".png");
         File input2 = new File("C:/Users/Mike/Desktop/eclipse/workspace/inClass/src/" + p2 + ".png");
         File input3 = new File("C:/Users/Mike/Desktop/eclipse/workspace/inClass/src/" + p3 + ".png");
         File input4 = new File("C:/Users/Mike/Desktop/eclipse/workspace/inClass/src/" + p4 + ".png");
         image1 = ImageIO.read(input1);
         image2 = ImageIO.read(input2);
         image3 = ImageIO.read(input3);
         image4 = ImageIO.read(input4);
     } catch (IOException ie) {
         System.out.println("Error:"+ie.getMessage());
     }
     repaint();
}

public oneplayer() {
    JPanel buttonPanel = new JPanel();
    setLayout(new BorderLayout());
    JButton refresh = new JButton("Refresh");
    refresh.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            redo();
        }
    });
    add(buttonPanel, BorderLayout.SOUTH);
    buttonPanel.add(refresh, BorderLayout.CENTER);
    redo();
}

public void paint(Graphics g) {
     g.drawImage(image1, 20, 55, null);
     g.drawImage(image2, 96, 55, null);
     g.drawImage(image3, 172, 55, null);
     g.drawImage(image4, 248, 55, null);
}

public static void main(String args[]) {
    oneplayer frame = new oneplayer();
    frame.setTitle("Random Cards");
    frame.setSize(350, 200);
    frame.setLocationRelativeTo(null);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setVisible(true);
}
}

Answer 1

Don't override paint() method. Instead override paintComponent() of main container.

Call super.paintComponent(g)

Don't extend JFrame but eg JPanel , add all you content to the panel and set the panel as a content pane of usual JFrame instance.

Answer 2

您需要在paint(Graphics)函数中调用super.paint(g)以确保正确显示框架内的Swing组件。

Answer 3

Haven't tested this with your sample, but I think you need to call the parent class's paint when overriding paint on your Frame in order for the Frame's components to show up. Like so:

public void paint(Graphics g) {
     super.paint(g);
     g.drawImage(image1, 20, 55, null);
     g.drawImage(image2, 96, 55, null);
     g.drawImage(image3, 172, 55, null);
     g.drawImage(image4, 248, 55, null);
}