Calling another JFrame/JPanel from another Class

Question

So I have this code in my main class:

import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.JLabel;

@SuppressWarnings("serial")
public class Main extends JPanel{

private final int height = 285;
private final int width = 416;   
private static final double appversion = 0.1;
private BufferedImage sdk001;
private static final String appname = "App's Name";
private static final String appstage = "Alpha";
private JFrame frame;

public Main() {
   try {                
        sdk001 = ImageIO.read(getClass().getResourceAsStream("img\\cards\\sdk001.png"));
        frame = new JFrame(appname + " (" + appversion + " " + appstage + ")");
        frame.add(new Main());
        frame.setSize(1020, 680);
        frame.setVisible(true);
        frame.setResizable(false);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setExtendedState(JFrame.MAXIMIZED_BOTH);
   } 
   catch (IOException e) {
       Logger LogErr = Logger.getLogger(Main.class.getName());
       System.err.println("Caught IOException: " + e.getMessage());
   }
}

@Override
protected void paintComponent(Graphics g) {
    super.paintComponent(g);
    g.drawImage(sdk001, 0, 0, height, width, null);
}

public static void main(String[] args) {
        Main main = new Main();
        JFrame frame = main.getFrame();
}

public JFrame getFrame() {
    return frame;
} 

And I tried to call it in my "A" class, here's the code:

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JLabel;
import java.awt.Graphics;
import java.awt.image.BufferedImage;

public class A {

public A(Main main){
    JFrame frame = main.getFrame();
    frame.add(new JLabel("Hi OtherClass did this") );
}

The code returns without error but no JFrame, or any GUI, showing up. Can anyone help me with this; I'm quite baffled by this. Thanks.

Answer 1

You need to initialize JFrame with new keyword and make it visible with preferred size, than you can view your GUI.

 Main main = new Main();
 JFrame frame = new JFrame(); //main.getFrame();
 frame.add(main); // Add JPanel with components to JFrame
 frame.setSize(300,300);
 frame.setVisible(true);