Whats causing all these errors in my GUI?

Question

I'm trying to work on my GUI coding so am taking it upon myself just to create several different interfaces for examples I had been given in class.

Im trying to create a GUI here that at the top has Labels followed by their respective text fields for the user to input, with one on top of the other. I then want this to be followed by a series of two buttons and finally a results field that is uneditable (as will later introduce some fields for results) and opaque. I get a whole series of errors so was wondering if I am just doing something stupid wrong.

The code for the panel is here:

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.BorderFactory;
import javax.swing.Box;
import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class GradePanel extends JPanel {

private JButton addEntry, calculate;
private JLabel name, grade;
private JTextField nameField, gradeField, resultField;

public GradePanel() {

    // Button to add entry to list
    addEntry = new JButton("Add entry to list");
   // addEntry.addActionListener(new tempListener());

    // Button to print all entries in correct format
    calculate = new JButton("Print all user grades");
   // calculate.addActionListener(new tempListener());

    //Create Labels
    name = new JLabel("Enter student name: ");
    nameField = new JTextField(10);
   // nameField.addActionListener(new tempListener());

    grade = new JLabel("Enter students mark: ");
    gradeField = new JTextField(5);
    // gradeField.addActionListener(new tempListener());

    //Bottom segment for result
    resultField = new JTextField();
    resultField.setOpaque(false);
    resultField.setEditable(false);

    setLayout(new BorderLayout());

    //Bottom Panel
    JPanel GradePanel = new JPanel();
    GradePanel.setBorder(BorderFactory.createTitledBorder("Students/Results"));
    GradePanel.setOpaque(false);
    GradePanel.add(resultField);

    //Button Panel
    JPanel ButtonPane = new JPanel();
    ButtonPane.add(addEntry, BoxLayout.LINE_AXIS);
    ButtonPane.add(calculate, BoxLayout.LINE_AXIS);

    //Label Panel
    JPanel labelPane = new JPanel();
    labelPane.add(name);
    labelPane.add(Box.createRigidArea(new Dimension (5,0)));
    labelPane.add(nameField);
    labelPane.add(Box.createRigidArea(new Dimension (0,2)));
    labelPane.add(grade);
    labelPane.add(Box.createRigidArea(new Dimension (5,0)));
    labelPane.add(gradeField);

    //Add all panels to the main panel
    add(labelPane, BorderLayout.NORTH); 
    add(ButtonPane, BorderLayout.CENTER);
    add(GradePanel, BorderLayout.SOUTH);

    setBackground(Color.WHITE);
    setPreferredSize(new Dimension(400, 300));
}

Thanks in advance!

EDIT: Forgot the errors:

Exception in thread "AWT-EventQueue-0" java.lang.IllegalArgumentException: illegal component position
    at java.awt.Container.addImpl(Container.java:1087)
    at java.awt.Container.add(Container.java:467)
    at GradePanel.<init>(GradePanel.java:55)
    at Grade$1.run(Grade.java:26)
    at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:756)
    at java.awt.EventQueue.access$500(EventQueue.java:97)
    at java.awt.EventQueue$3.run(EventQueue.java:709)
    at java.awt.EventQueue$3.run(EventQueue.java:703)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:726)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

EDIT 2:

public class GradePanel2 extends JPanel {

    private JButton addEntry, calculate;
    private JLabel name, grade;
    private JTextField nameField, gradeField, resultField;

    public GradePanel2() {

        // Button to add entry to list
        addEntry = new JButton("Add entry to list");
        // addEntry.addActionListener(new tempListener());

        // Button to print all entries in correct format
        calculate = new JButton("Print all user grades");
        // calculate.addActionListener(new tempListener());

        // Create Labels
        name = new JLabel("Enter student name: ");
        nameField = new JTextField(10);
        // nameField.addActionListener(new tempListener());

        grade = new JLabel("Enter students mark: ");
        gradeField = new JTextField(5);
        // gradeField.addActionListener(new tempListener());

        // Bottom segment for result
        resultField = new JTextField();
        resultField.setOpaque(false);
        resultField.setEditable(false);

        setLayout(new BorderLayout());

        // Bottom Panel
        JPanel GradePanel = new JPanel();
        GradePanel.setBorder(BorderFactory.createTitledBorder("Students/Results"));
        GradePanel.setOpaque(false);
        GradePanel.add(resultField);

        // Button Panel
        JPanel ButtonPane = new JPanel();
        ButtonPane.setLayout(new BoxLayout(ButtonPane, BoxLayout.PAGE_AXIS));
        ButtonPane.add(addEntry, BoxLayout.LINE_AXIS);
        ButtonPane.add(calculate, BoxLayout.LINE_AXIS);

        // Label Panel
        JPanel labelPane = new JPanel();
        labelPane.setLayout(new BoxLayout(labelPane, BoxLayout.PAGE_AXIS));
        labelPane.add(name);
        labelPane.add(Box.createRigidArea(new Dimension(5, 0)));
        labelPane.add(nameField);
        labelPane.add(Box.createRigidArea(new Dimension(0, 2)));
        labelPane.add(grade);
        labelPane.add(Box.createRigidArea(new Dimension(5, 0)));
        labelPane.add(gradeField);

        // Add all panels to the main panel
        add(labelPane, BorderLayout.NORTH);
        add(ButtonPane, BorderLayout.CENTER);
        add(GradePanel, BorderLayout.SOUTH);

        setBackground(Color.WHITE);
        setPreferredSize(new Dimension(400, 300));
    }

}

`ButtonPane` is using a `FlowLayout`, but you seem to be trying to apply `BoxLayout` constraints to it which is confusing the API making it think you're trying to insert a component at a given location within it's list, which doesn't exist, hence the *"Exception in thread "AWT-EventQueue-0" java.lang.IllegalArgumentException: illegal component position"* exception — MadProgrammer, Mar 24 '16 at 01:40
Maybe you should take a closer look at [Laying Out Components Within a Container](http://docs.oracle.com/javase/tutorial/uiswing/layout/index.html) — MadProgrammer, Mar 24 '16 at 01:41
BTW - quite often compiler errors on line N will **cause** compiler errors on lines >N. So deal with the first one, first. Speaking of which: Always copy/paste error and exception output! — Andrew Thompson, Mar 24 '16 at 01:41
Please learn common Java nomenclature (naming conventions - e.g. `EachWordUpperCaseClass`, `firstWordLowerCaseMethod()`, `firstWordLowerCaseAttribute` unless it is an `UPPER_CASE_CONSTANT`) and use it consistently. — Andrew Thompson, Mar 24 '16 at 01:42
Added errors. @MadProgrammer I will certainly have a read, like I said Im doing all this to try and get fluent with it so any resources are a great help. Could you explain where about I have made ButtonPane run as a FlowLayout? — SkyPlus, Mar 24 '16 at 01:45
@SkyPlus The default layout for a `JPanel` is `FlowLayout`, so the moment you did `new JPanel()` you started using `FlowLayout` — MadProgrammer, Mar 24 '16 at 01:46
@MadProgrammer I see, that makes sense. So I have probably created errors in the other parts such as labels etc too then? Would a .setLayout help in this instance to fix the problem? Thanks — SkyPlus, Mar 24 '16 at 01:50
@SkyPlus IMHO, I'd be looking towards `GridBagLayout`, but I'm more familiar with it then I am with `BoxLayout` — MadProgrammer, Mar 24 '16 at 01:57
See [What is a stack trace, and how can I use it to debug my application errors?](http://stackoverflow.com/q/3988788/418556) — Andrew Thompson, Mar 24 '16 at 11:10

score 1 · Answer 1 · answered Mar 24 '16 at 01:45

1

You're applying BoxLayout constraints to a JPanel which is using a FlowLayout by default...

JPanel ButtonPane = new JPanel();
ButtonPane.add(addEntry, BoxLayout.LINE_AXIS);
ButtonPane.add(calculate, BoxLayout.LINE_AXIS);

which is causing a

Exception in thread "AWT-EventQueue-0" java.lang.IllegalArgumentException: illegal component position
    at java.awt.Container.addImpl(Container.java:1085)
    at java.awt.Container.add(Container.java:465)
    at javaapplication866.JavaApplication866$GradePanel.<init>(JavaApplication866.java:98)

Perhaps you should start by haiving a look at How to Use BoxLayout

answered Mar 24 '16 at 01:45

MadProgrammer

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Still getting an error after making some changes, any idea whats causing it now? – SkyPlus Mar 24 '16 at 02:09
Will come back and try it tomorrow with the GridBagLayout and start over but should try and fix this too to learn my errors. Thanks for the help – SkyPlus Mar 24 '16 at 02:15

Whats causing all these errors in my GUI?

1 Answers1