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!

MadProgrammer · Accepted Answer · 2016-02-13T02:51:54.110

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)

But how come it worked one time but not the other? Shouldn't it either always work or never work? — akarshkumar0101, Feb 13 '16 at 02:50
See update, it's possible you have a race condition between the "main" thread and the Event Dispatching Thread (among other things) — MadProgrammer, Feb 13 '16 at 02:52
That makes sense that one time the main method might have reached set bounds before the frame was actually displayed...Alright thanks! — akarshkumar0101, Feb 13 '16 at 02:55

Java Swing elements change every runtime

1 Answers1