JFrame not adding JPanel in Eclipse Neon

Question

public class DrawablePanel extends JPanel {

    public static void main(String[] args) {
        JFrame frame = new JFrame();
        
        frame.setSize(500,500);
        frame.setLayout(null);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(new DrawablePanel());
        frame.setVisible(true);
    }

    public DrawablePanel(){
        setBackground(Color.black);
     }

    public Color pickColor(){
        Random rand = new Random();
        int a = rand.nextInt(255)+0;
        int b = rand.nextInt(255)+0;
        int c = rand.nextInt(255)+0;
        Color color = new Color(a,b,c);
        return color;
    }
}

I have no idea why the JPanel is not showing up on the JFrame. I have attached an image of what it looks like when I run the code.

I forgot to mention that I have also already re-downloaded Eclipse — Calvin Stineburg, Apr 28 '17 at 00:16
Do you understand what happens when you call `setLayout(null)`? Do you understand what the layout management API does? — MadProgrammer, Apr 28 '17 at 00:34
`frame.setLayout(null);` We have to deal with this at least once a day, two or three times on some days. Java GUIs have to work on different OS', screen size, screen resolution etc. using different PLAFs in different locales. As such, they are not conducive to pixel perfect layout. Instead use layout managers, or [combinations of them](http://stackoverflow.com/a/5630271/418556) along with layout padding and borders for [white space](http://stackoverflow.com/a/17874718/418556). — Andrew Thompson, Apr 28 '17 at 00:34
@MadProgrammer Is there a canonical Q&A that can be used to close this as a dupe? — Code-Apprentice, Apr 28 '17 at 00:38
did you notice that you are assigning a `null` to the `Layout` check this line: `frame.setLayout(null);` — Teocci, Apr 28 '17 at 00:39
@Code-Apprentice Probably, but I'm kind of over doing all the searching — MadProgrammer, Apr 28 '17 at 00:40
@MadProgrammer Me, too. And I haven't been in the Java tag for a while. I'll just reference this for future dupes ;-) — Code-Apprentice, Apr 28 '17 at 00:41

Code-Apprentice · Accepted Answer · 2017-04-28T00:58:39.967

3

frame.setLayout(null);

This line removes the Layout Manager. To fix the immediate problem, just remove this line and you will get the expected black background. Then you need to learn how to use Layout Managers. The Swing API provides many options. Which one you choose depends on the look you want your program to have. I suggest checking out A Visual Guide to Layout Managers to get an overview of the most common Layout Managers.

edited Apr 28 '17 at 00:58

answered Apr 28 '17 at 00:36

Code-Apprentice

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@AndrewThompson Thanks for the feedback. Feel free to edit my answer to improve the wording there. – Code-Apprentice Apr 28 '17 at 00:49
@AndrewThompson okay...I took the time to edit it myself. Let's clean up the comments now. – Code-Apprentice Apr 28 '17 at 00:59

JFrame not adding JPanel in Eclipse Neon

1 Answers1