Java Swing elements change every runtime

Question

So I made a program using java's swing library. I made a program that graphs equations and here is the main method if it's relevant:

public static void main(String[] args) throws Exception {

    JFrame frame= new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setVisible(true);

    frame.setLayout(new GridLayout(1,2));

    GraphPanel gp = new GraphPanel();
    GraphPanel gp2 = new GraphPanel();

    //gp.functs.add(new Function(Phrase.createPhrase("2(25-x^2)^(1/2)")));
    //gp.functs.add(new Function(Phrase.createPhrase("-1.1((25-x^2)^(1/2))")));
    gp.functs.add(new Function(Phrase.createPhrase("x^2")));
    //gp.functs.add(new Function(Phrase.createPhrase("-4/x^2+6")));
    gp2.functs.add(new Function(Phrase.createPhrase("sinx")));

    frame.add(gp);
    frame.add(gp2);
    frame.pack();
    frame.setSize(800, 800);


    //gp.setBorder(BorderFactory.createLineBorder(Color.RED));
    gp.setBounds(100, 100, 700, 700);//I WANT THIS TO ALWAYS RUN

}

I ran two trial runs of the program WITHOUT CHANGING ANY PART OF IT and this is what it looked like:

Then the next time i ran it:

If it's relevant, GraphPanel is of type JLabel. I know that if i use a null absolute LayoutManager, it will always work. But I'm just wondering why swing has such inconsistencies in it. I've noticed stuff like this before but I though it was just some error in the program. Why is this? Thanks in advance!

Answer 1

• Start by moving frame.setVisible(true); to the end of the main method
• This gp.setBounds(100, 100, 700, 700); is pointless, as gp is under the control of a layout manager ( GridLayout )
• There's no point in using both path and setSize , pack is generally a safer option, but that will depend on your components correctly overriding getPreferredSize

But I'm just wondering why swing has such inconsistencies in it. I've noticed stuff like this before but I though it was just some error in the program. Why is this?

Mostly because you're not using the API properly. It's possible, because of the way a JFrame is physically attached to a native peer, that the frame may or may not actually be visible on the screen when you reach gp.setBounds .

Also, because you're doing all your work from within the "main" thread and not the Event Dispatching Thread, you're running the risk of a race condition between them, see Initial Threads for more details.

Swing is VERY flexible, it's also unforgiving when you do the wrong things (or things the wrong way)