Imported Class of Components are Hidden

I'm not sure how to word this, but I did my best in the title. I'm creating a GUI and for simplicity it has a frame, a tabbed pane, a panel, and a button. Originally, they started in the same class, but I want to try splitting them into two classes.

So now I have this...

Code java:

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import FirstPanel.java
 
public class GUI extends JFrame{
private JFrame frame;
private JTabbedPane tabs;
private FirstPanel firstPanel;
 
//Constructor
public GUI(){
frame = new JFrame();
tabs = new JTabbedPane();
firstPanel = new FirstPanel();
 
tabs.add("Tab #1", firstPanel);
frame.add(tabs);
//Set frame visible and the size etc...
 
}
 
public static void main(String[] args){
GUI gui = new GUI();
gui.setVisible(true);
}

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What is FirstPanel? It's the second class!

Code java:

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public class FirstPanel extends JPanel{
private JPanel panel;
private JButton button;
 
//Constructor
public FirstPanel(){
 
panel = new JPanel();
button = new JButton("Why can't you see me?");
 
panel.add(button);
}
}

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The output I am looking for is a frame with a tab with a panel with a button.

Now, when I run GUI, I get a frame with a tab with a panel but there is no button displayed. I thought at first that it was because all components need to be in the same class, but I dismiss that because I am at least getting ONE panel.

I get no errors or output from this, only a missing button.

Any help is greatly appreciated!
Cheers!
-Polaris395 :confused:

FirstPanel IS A JPanel (it extends JPanel). It also HAS A JPanel (named panel). You're adding the JButton to the HAS A JPanel, but you're adding the IS A JPanel to the JFrame.

Oh! Duh! I guess I've been looking at my code to long to notice that, lol.

Thanks!

Quote:

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Originally Posted by polaris395

Oh! Duh! I guess I've been looking at my code to long to notice that, lol.

Thanks!

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No problem. This is one reason people argue for "composition over inheritance". If FirstPanel doesn't actually modify the functionality of JPanel, there's no reason for it to extend JPanel. Instead, just have a getPanel() method that returns the JPanel after whatever initialization is done. I might not be explaining it that great, but a google of "composition over inheritance" brings back some good results.