JPanel 未在 Java 中的 JFrame 内显示

Question

I know this question has been asked a lot and I have done my research but still can not find anything. Below is proof of this before anyone gets upset:

I found this link: https://coderanch.com/t/563764/java/Blank-Frame-Panel

and this: Adding panels to frame, but not showing when app is run

and this: Why shouldn't I call setVisible(true) before adding components?

and this: JPanel not showing in JFrame?

But the first question says use repaint which I tried with no fix and the second and third to last questions talk about putting setVisible after components added which I have.

The last one talks about making the users JPanelArt a extension (done so) of JPanel instead of JFrame and not to make a frame in a frame constructor (also have not done)

When ever I run this I just get a blank frame, as if the panel was never added in.

I apologise if I have missed something in those links. Anyway below is my classes:

GUI.java (extends JFrame)

package javaapplication2;

import javax.swing.JFrame;
import javax.swing.JPanel;

public class GUI extends JFrame{

public GUI(String name) {
    super(name);

    getContentPane().setLayout(null);

    JPanel myPanel1 = new GUIPanel();
    myPanel1.setLocation(20, 20);
    getContentPane().add(myPanel1);

    setDefaultCloseOperation(EXIT_ON_CLOSE);
    pack();
    setResizable(true);
}

public static void main(String[] args) {
    JFrame frame = new GUI("Game");
    frame.setVisible(true);
}
}

GUIPanel.java (extends JPanel)

package javaapplication2;

import java.awt.*;   
import javax.swing.*;


public class GUIPanel extends JPanel {

JButton start;
JButton inspect1;
JButton inspect2;
JButton inspect3;
JButton suspect;

public GUIPanel() {
    setLayout(new BorderLayout());

    start = new JButton("Start Game");
    inspect1 = new JButton("Inspect 1");
    inspect2 = new JButton("Inspect 2");
    inspect3 = new JButton("Inspect 3");
    suspect = new JButton("Choose Suspect");

    add(start, BorderLayout.WEST);
    add(inspect1, BorderLayout.WEST);
    add(inspect2, BorderLayout.WEST);
    add(inspect3, BorderLayout.WEST);
    add(suspect, BorderLayout.WEST);

}
}

I know it is very simple, but that is because I am following a tutorial from my lecturer to get the hang of things as I previously used a GUI builder which someone in this community pointed out to me is not good to start with (very correct!)

Answer 1

The issue lies in your GUI class when you call getContentPane().setLayout(null) . Because of this method call, your JFrame is not displaying anything. If you remove it, your elements should show up.

I also noticed that you were setting each JButton to have a constraint of BorderLayout.WEST . This will most likely put your JButtons on top of each other and render only one of them.