Develop Reference

How to make a JButtons appear

I want to make a JButton that lies on the NorthPane of the frame, but when I run the program there's no button. Why does it do that?
I'm using IntelliJ IDEA.
BTW I'm posting this question again, cause the first time I didn't get the desired answer.
Here's my code.
package com.company;
import javax.swing.*;
import javax.swing.border.Border;
import java.awt.*;
class Fantasyrpglifesim implements JButton {
Fantasyrpglifesim() {
}
public static void main(String[] args) {
MouseInputAdapter();
//Frame//
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(WindowConstants.HIDE_ON_CLOSE);
frame.setSize(1500, 1500);
frame.getContentPane();
frame.setVisible(true);
JPanel mainPanel = new JPanel(new BorderLayout());
JPanel northPanel = new JPanel();
mainPanel.add(northPanel,BorderLayout.NORTH );
//frame.setLayout(new FlowLayout());//
//Buttons//
frame.add(BUTTON);
BUTTON.setText("Age up");
northPanel.add(BUTTON);
northPanel.add(BUTTON1);
BUTTON1.setText("Test");
northPanel.add(BUTTON2);
BUTTON2.setText("Test1");
northPanel.add(BUTTON2);
BUTTON2.setText("Test2");
northPanel.add(BUTTON3);
BUTTON3.setText("Test3");
northPanel.add(BUTTON4);
BUTTON4.setText("Test4");
northPanel.add(BUTTON5);
BUTTON5.setText("Test5");
northPanel.add(BUTTON6);
BUTTON6.setText("Test6");
northPanel.add(BUTTON7);
BUTTON7.setText("Test7");
northPanel.add(BUTTON8);
BUTTON8.setText("Test8");
northPanel.add(BUTTON9);
BUTTON9.setText("Test9");
northPanel.add(BUTTON10);
BUTTON10.setText("Test10");
northPanel.add(BUTTON11);
BUTTON11.setText("Test11");
northPanel.add(BUTTON12);
BUTTON12.setText("Test12");
northPanel.add(BUTTON13);
BUTTON13.setText("Test13");
northPanel.setVisible(true);
//panels//
//mainPanel.add(northPanel, BorderLayout.NORTH);//
}
private static void MouseInputAdapter() {
}
}

to add a JButton you have to create a JButton object and add that to the JPanel.
And you need to define it for EVERY button that you want to have.
anywhere. I'm surprised your compiler isn't flagging that
Anyway what you want should look sth like this
JButton testButton = new JButton("test");
northPanel.add(testButton);

First, I want you to check your compiler and IntelliJ cause they're not working if you can run the code you posted.
You cannot implement a JButton unless you have made an interface yourself.
Cause the JButton is not an interface.
No need to set a BorderLayout for your JPanel. FlowLayout will do the job.
Use a for loop to avoid duplicate code.
Learn how to use Swing components.
import javax.swing.*;
import java.awt.*;
class Fantasyrpglifesim {
private static int count = 1;
public static void main(String[] args) {
JFrame frame = new JFrame();
JPanel mainPanel = new JPanel();
JButton age = new JButton("Age up");
mainPanel.add(age);
for (int x=0; x<14;x++){
JButton button = new JButton();
button.setText("Test"+ count++);
mainPanel.add(button);
}
frame.getContentPane().add(BorderLayout.NORTH,mainPanel);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(1500, 1500);
frame.setVisible(true);
}
}
Is this your desired output?

Java GUI, transitioning from one class to another

I am stumped and desperate for help. Been able to figure everything else out until I got into GUI's. What I am trying to do is go from the LogInPane (Log In Page) to JobSelectionGUI (Job Selection Page);
When I compile it runs how I want it to, but I can't figure out how to get my JFrame from LogInPaneGUI to close when it opens JobSelectionGUI, Tons of reading and videos and picking GUI's/Applying them is rough! I started with a GridLayout then switched to GridBagLAyout, then tried CardLayout and now back to GBL.
I don't use an IDE; I use SublimeText, so if something looks extremely elongated in my code, its because I had to write it out long for Sublime (or because I'm bad). All my code is separated into different classes so it stays neat and easy to debug. Every class has its own package, and every package has no more than 2 Methods. I work my butt off to keep my main completely empty!
Taking all criticism and advice!
MAIN:
package com.hallquist.kurtis.leigh.srcmain;
import java.awt.*;
import javax.swing.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.text.*;
// Class imports;
import JobSelection.*;
import LogInPane.*;
// My Main function. Used to pull packages and methods and compile them here;
public class SrcMainUserInformation{
public static void main(String[] args){
LogInPaneGUI logInGUI = new LogInPaneGUI();
logInGUI.logInPaneMainGUI();
}
}
First Class:
package LogInPane; // package name;
import java.awt.*;
import javax.swing.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.ImageIcon;
import JobSelection.*; //import for next GUI when LogInButton is clicked;
public class LogInPaneGUI{
private static final JFrame frame = new JFrame();
private static final int COLS = 10; // Max columns;
private static final JPanel panelForm = new JPanel(new GridBagLayout()); // layout
private static final JTextField fieldLogInName = new JTextField(COLS); //login
private static final JPasswordField logInPassword = new JPasswordField(COLS); //pw
private static final JButton logInButton = new JButton("Log In"); //login button
private static final JButton exitButton = new JButton("EXIT"); //system.exit button
private static final JButton newUser = new JButton("New User? Click here to sign up!"); // new user button
// Wigits on login page;
public LogInPaneGUI(){
GridBagConstraints c = new GridBagConstraints();
// Creates the panel that goes ontop of the JFrame;
c.gridx = 0;
c.gridy = 0;
c.anchor = GridBagConstraints.LINE_END;
panelForm.add(new JLabel("Account Name: "), c);
c.gridy ++;
panelForm.add(new JLabel("Password: "), c);
c.gridy ++;
c.gridx = 1;
c.gridy = 0;
c.anchor = GridBagConstraints.LINE_START;
panelForm.add(fieldLogInName, c);
c.gridy++;
panelForm.add(logInPassword, c);
c.gridy++;
panelForm.add(logInButton, c);
c.gridy++;
panelForm.add(newUser, c);
c.gridy++;
panelForm.add(exitButton, c);
// Goes to fourm/website on newUser click;
newUser.addActionListener(new ActionListener(){
#Override
public void actionPerformed(ActionEvent e){
System.out.println("Fourm/Website to sign up for game");
}
});
// Exits program on exitButton click;
exitButton.addActionListener(new ActionListener(){
#Override
public void actionPerformed(ActionEvent e){
System.exit(0);
}
});
// Goes to JobSelectionGUI on logInButton Click;
logInButton.addActionListener(new ActionListener(){
#Override
public void actionPerformed(ActionEvent e){
JobSelectionGUI jobSelecting = new JobSelectionGUI();
jobSelecting.jobSelectionJFrameGUI();
// frame.dispose();
// System.out.println("Will log you in when I set it up");
}
});
}
// Actual JFrame that everything goes ontop of;
public static void logInPaneMainGUI(){
JFrame frame = new JFrame("FirstProject");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.setSize(1080, 720);
frame.setResizable(false);
frame.setVisible(true);
frame.setLocationRelativeTo(null);
frame.getContentPane().add(panelForm);
}
}
Second Class:
package JobSelection;
import java.awt.*;
import java.awt.event.ActionEvent.*;
import javax.swing.*;
import javax.swing.text.*;
// Mass import from JobSelection package; All base job information;
import JobSelection.JobInformationIndex.JobAmazonData.*;
import JobSelection.JobInformationIndex.JobBanditData.*;
import JobSelection.JobInformationIndex.JobLancerData.*;
import JobSelection.JobInformationIndex.JobSorcererData.*;
import JobSelection.JobInformationIndex.JobWitchData.*;
import LogInPane.*; // to return to login screen;
import JobSelection.*; // dont know if needed;
public class JobSelectionGUI{
private static JFrame frame = new JFrame();
private static JSplitPane jSplitPane = new JSplitPane();
private static JPanel leftPane = new JPanel();
private static JLabel logInCharacterName = new JLabel();
private static JTextField userCharacterName = new JTextField();
private static JButton logInAccept = new JButton("Accept");
private static JButton logInBack = new JButton("Back");
private static JTextArea firstGameIntroduction = new JTextArea();
private static JTextArea descriptionIntroduction = new JTextArea();
private static JTextArea jobSelectedInformation = new JTextArea();
private static JPanel allWidgits = new JPanel();
public JobSelectionGUI(){
JTextArea firstGameIntroduction = new JTextArea("\ Text.");
firstGameIntroduction.setLineWrap(true);
firstGameIntroduction.setWrapStyleWord(true);
JScrollPane areaScrollPane = new JScrollPane(firstGameIntroduction);
areaScrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
areaScrollPane.setPreferredSize(new Dimension(250, 250));
areaScrollPane.setBorder(
BorderFactory.createCompoundBorder(
BorderFactory.createCompoundBorder(
BorderFactory.createTitledBorder("Introduction"),
BorderFactory.createEmptyBorder(5,5,5,5)),
areaScrollPane.getBorder()));
leftPane.add(areaScrollPane);
JTextArea descriptionIntroduction = new JTextArea(" Text.\n");
descriptionIntroduction.setLineWrap(true);
descriptionIntroduction.setWrapStyleWord(true);
JScrollPane areaScrollPaneTwo = new JScrollPane(descriptionIntroduction);
areaScrollPaneTwo.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
areaScrollPaneTwo.setPreferredSize(new Dimension(250, 250));
areaScrollPaneTwo.setBorder(
BorderFactory.createCompoundBorder(
BorderFactory.createCompoundBorder(
BorderFactory.createTitledBorder("What to expect"),
BorderFactory.createEmptyBorder(5,5,5,5)),
areaScrollPaneTwo.getBorder()));
leftPane.add(areaScrollPaneTwo);
}
public static void jobSelectionJFrameGUI(){
JFrame frame = new JFrame("FirstProject");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(1080, 720);
frame.setResizable(false);
frame.setVisible(true);
frame.setLocationRelativeTo(null);
frame.getContentPane().add(leftPane);
}
}

You grossly overuse the static modifier and most of your fields should not in fact be static. I would venture to state that most if not all of your class's fields should be private instance fields.
The log-in window should not be a JFrame but rather a blocking or "modal" dialog, and for Swing that means using a modal JDialog or JOptionPane (which creates a modal JDialog behind the scenes)
A modal dialog will block the calling code when it is displayed
And if the dialog is modal, then you know when it is no longer visible since the calling code is unblocked. This is when you would query the state of the dialog's fields (using public getter methods, not calling static fields directly), and decide if the login was successful or not. If so, show your main GUI window or JFrame.
Another option is to yes, use CardLayout, but for this to work, all your major GUI classes should be geared towards creating JPanels, not JFrames. This way you can insert the panels where and when needed, including within top-level windows such as JFrames or JDialogs, within or JPanels, or swapped using a CardLayout.
Note that frame.dispose() isn't working for you because you shadow the frame field by re-declaring it logInPaneMainGUI() method.
public static void logInPaneMainGUI() {
// ***** this creates a new local JFrame variable called frame
JFrame frame = new JFrame("FirstProject");
// so calling frame.dispose() elsewhere will have no effect on this window
Don't do this, and the .dispose() method call will close the first window.
public static void logInPaneMainGUI() {
frame = new JFrame("FirstProject"); // this initializes the frame field
// so calling frame.dispose() elsewhere will have no effect on this window
Of course frame would have to be non-final or not-initialized previously. I still would recommend using a JDialog however, as well as moving out of the static world and into the instance world
Unrelated criticism:
Less chatty text in your question, text that is completely unrelated to your actual problem at hand, and more text that tells us useful information that helps us to understand your problem and your code, and thereby helping us solve the problem.

Nothing is appearing when i switch JPanels

Im rather new at Java, I am have created a home page and a few buttons, When i click one of the buttons it sets the homepage panel visibility to false, opens a new class and sets that classes Jpanel to visible.
homePanel.setVisible(false);
Goodsin Barcode = new Goodsin();
Goodsin.setVisible(true);
However once it opens the new class "Goodsin" it wont show any of the Buttons or TextFileds. I know it is opening the new class as a System.out.println prints to the console but nothing displays in the JFrame and i do not know why.
Here is my code of the new class
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
public class Goodsin {
public JPanel Goodsin;
public JTextField item1;
public String code;
public JButton btn1;
public Goodsin() {
System.out.println("TEST");
Goodsin = new JPanel();
item1 = new JTextField(10);
btn1 = new JButton("Look up Barcode");
Goodsin.setVisible(true);
Goodsin.add(item1);
item1.setSize(80, 30);
Goodsin.add(btn1);
btn1.setSize(80, 30);
}
public void getString(String code) {
System.out.println(code);
}
}
Im sure i am not doing something correct with the Jpanel or adding the textfields or button but all the answers i have seen so far havnt worked.

I suggest you add your panels to a JFrame. You can either do this by extending JFrame from the class or simply instantiating one in your constructor. Then you can simply add and remove (or set visible/invisible) as you wish. Be sure to validate your JFrame/JPanel after changing visibility though.

Try to do something like this:
Goodsin = new JPanel();
item1 = new JTextField(10);
btn1 = new JButton("Look up Barcode");
item1.setSize(80, 30);
Goodsin.add(item1);
btn1.setSize(80, 30);
Goodsin.add(btn1);
JFrame frame = new JFrame("JFrame Example");
Goodsin.setLayout(new FlowLayout());
frame.add(Goodsin);

I suggest you try the following code :
public class Goodsin extends JFrame{
public static void main(String[] args) {
Goodsin ui = new Goodsin();
JTextField item1 = new JTextField(10);
JButton btn1 = new JButton("Look up Barcode");
JPanel centralPanel = new JPanel(new FlowLayout());
centralPanel.add(item1);
centralPanel.add(btn1);
item1.setSize(80, 30);
btn1.setSize(80, 30);
ui.add(centralPanel);
ui.pack();
ui.setVisible(true);
}
}
Everything is done in the main method in my example, however you still can improve this code and refactor it in a better way.

just you have to set Bounds of Goodsin panel or set Size and add in home page frame

How to reference JFrame

I have a problem which is most likely "simple" however I can't figure it out. I am trying to reference my current JFrame so that I can dispose of it, and create a new one, thus "resetting" the program, however I and having trouble figuring out how to reference the JFrame, I have tried, super, this and getParent(), but none of the seem to work. Thanks for any / all help. ^^
Here is my code:
Main Class, just sets up the Jframe and calls the class that creates everything:
public static void main(String args[]) {
JFrame window = new JFrame();
Director director = new Director(window, args);
window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
window.setLocationRelativeTo(null);
window.pack();
window.setVisible(true);
}
}
Class the creates everything:
import java.awt.Color;
import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.ButtonGroup;
import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JRadioButton;
public class Director extends JFrame implements CollisionListener {
private BrickWall wall;
private JLabel gameTitle, gameScore, gameLives;
private JPanel controlPanel;
private JButton reset, quit;
private JRadioButton hard, normal, easy;
private int score = 6, lives = 5;
private ButtonGroup difficulty;
public Director(JFrame window, String[] args) {
window.getContentPane().add(makeGamePanel(), BorderLayout.CENTER);
window.getContentPane().add(gameControlPanel(), BorderLayout.NORTH);
}
public void collisionDetected(CollisionEvent e) {
wall.setBrick(e.getRow(), e.getColumn(), null);
}
private JComponent makeGamePanel() {
wall = new BrickWall();
wall.addCollisionListener(this);
wall.buildWall(3, 6, 1, wall.getColumns(), Color.GRAY);
return wall;
}
// Reset method I'm trying to dispose of the JFrame in.
private void reset() {
JFrame frame = new JFrame();
frame.getContentPane().add(makeGamePanel(), BorderLayout.CENTER);
frame.getContentPane().add(gameControlPanel(), BorderLayout.NORTH);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setVisible(true);
}
private JComponent gameControlPanel() {
// CONTROL PANEL PANEL!
controlPanel = new JPanel();
gameTitle = new JLabel("Brickles");
gameScore = new JLabel("Score:" + " " + score);
gameLives = new JLabel("Lives:" + " " + lives);
reset = new JButton("Reset");
quit = new JButton("Quit");
hard = new JRadioButton("Hard", false);
normal = new JRadioButton("Normal", true);
easy = new JRadioButton("Easy", false);
difficulty = new ButtonGroup();
difficulty.add(hard);
difficulty.add(normal);
difficulty.add(easy);
controlPanel.setLayout(new GridLayout(4, 2));
controlPanel.add(gameTitle);
controlPanel.add(gameScore);
controlPanel.add(hard);
controlPanel.add(gameLives);
controlPanel.add(normal);
controlPanel.add(reset);
controlPanel.add(easy);
controlPanel.add(quit);
// Action Listener, where I'm caling the reset method.
reset.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
reset();
}
});
return controlPanel;
}
}

You can refer to the "outer this" from a nested class with the following syntax:
reset.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
Director.this.reset();
}
});

Yes, you can refer to the outer class by specifying it with the class name as noted in DSquare's good answer (1+ to it), but I urge you not to fling JFrame's at the user as you're program is trying to do. I recommend:
Instead of opening and closing multiple JFrames, use only one JFrame as the main application's window.
If you need helper windows, such as modal windows to get critical information that is absolutely needed, before the program can progress, use modal dialogs such as JDialogs or JOptionPanes.
If you need to swap GUI's, instead of swapping JFrames, swap "views" inside the JFrame via a CardLayout.
Gear your code towards creating these JPanel views and not JFrames as it will make your Swing GUI's much more flexible and portable.

JPanels not added to JTabbedPane

For my homework extra credit I am creating a JTabbedPane and adding two Jpanels. I feel like I am very close, but it still does not compile. When I run it, both JPanels open, but the JTabbedPane does not. I get a lot of Unknown Source errors. I suspect that at this point my issue in in the JPanels themselves because they started out being JFrames and I have tried (unsuccessfully I think) to convert the JFrames to JPanels.
JTabbedPaneAssignment is supposed to create the JTabbedPane and populate the two panes with the apps DayGui on one tab and OfficeAreaCalculator on the other. I only include the JTabbedPaneAssignment and DayGui classes here. I apologize if its too much code, I have trimmed off a lot of what I consider extraneous, but there may still be too much.
Here is the calling class JTabbedPaneAssignment
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class JTabbedPaneAssignment extends JPanel
{
public JTabbedPaneAssignment()
{
//super(new GridLayout(1, 1));
JTabbedPane tabbedPane = new JTabbedPane();
DayGui pnlDay = new DayGui();
OfficeAreaCalculator pnlOffice = new OfficeAreaCalculator ();
this.add(tabbedPane);
JPanel panel1 = new JPanel();
JPanel panel2 = new JPanel();
tabbedPane.add(panel1,"First panel");
tabbedPane.add(panel2,"Second panel");
//JComponent panel1 = makeTextPanel("Pane #1");
panel1.setPreferredSize(new Dimension(300, 150));
tabbedPane.addTab("DayGui", panel1);
tabbedPane.setMnemonicAt(0, KeyEvent.VK_1);
//JComponent panel2 = makeTextPanel("Pane #2");
panel2.setPreferredSize(new Dimension(410, 50));
tabbedPane.addTab("OfficeAreaCalculator", panel2);
tabbedPane.setMnemonicAt(1, KeyEvent.VK_2);
add(tabbedPane);
}
protected JComponent makeTextPanel(String text)
{
JPanel panel = new JPanel(false);
JLabel filler = new JLabel(text);
filler.setHorizontalAlignment(JLabel.CENTER);
panel.setLayout(new GridLayout(1, 1));
panel.add(filler);
return panel;
}
// Create JTabbedPane
private static void createAndShowGUI()
{
// Create and set up the window.
JFrame frame = new JFrame("JTabbedPane");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new JTabbedPaneAssignment(), BorderLayout.CENTER);
JTabbedPane DayGui = new JTabbedPane();
JTabbedPane OfficeAreaCalculator = new JTabbedPane();
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args)
{
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
createAndShowGUI();
}
});
}
}
Here is DayGui class. It started out as a JFrame, but I am trying to convert it to a JPanel. I think my issue is in this section of code, but I don't know
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
//public class DayGui extends JPanel
public class DayGui extends JPanel
{
private JPanel dayPanel;
private JButton cmdGood;
private JButton cmdBad;
public DayGui()
{
//dayPanel = new JPanel("Messages");
cmdGood = new JButton("Good");
cmdBad = new JButton("Bad");
Container c = dayPanel.getRootPane();
c.setLayout(new FlowLayout());
c.add(cmdGood);
c.add(cmdBad);
dayPanel.setSize(300, 150);
ButtonsHandler bhandler = new ButtonsHandler();
cmdGood.addActionListener(bhandler);
cmdBad.addActionListener(bhandler);
dayPanel.setVisible(true);
dayPanel.getRootPane().setBackground(Color.CYAN);
}
class ButtonsHandler implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
if (e.getSource() == cmdGood)
JOptionPane.showMessageDialog(null, "Today is a good day!",
"Event Handler Message",
JOptionPane.INFORMATION_MESSAGE);
if (e.getSource() == cmdBad)
JOptionPane.showMessageDialog(null, "Today is a bad day!",
"Event Handler Message",
JOptionPane.INFORMATION_MESSAGE);
}
}
}

You have been very ambiguous with your question, and you've posted way more code than anyone here has time to trawl through.
I've made a very small but working JTabbedPane example for you to see the smallest amount of work you need to get it working.
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTabbedPane;
public class JTabbedPaneExample extends JFrame{
public JTabbedPaneExample(String title){
super(title);
setSize(800,600);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLocationRelativeTo(null);
JTabbedPane tabbedPane = new JTabbedPane();
JPanel panelOne = new JPanel();
JPanel panelTwo = new JPanel();
tabbedPane.add(panelOne,"First panel");
tabbedPane.add(panelTwo,"Second panel");
add(tabbedPane);
}
public static void main(String[] args){
new JTabbedPaneExample("JTP Example").setVisible(true);
}
}
Then running, this code looks like:
If you repeat the same process in your code, and you've still got errors, then the problem is not with your JTabbedPane, but something else.

Okay, here goes a second time. Now you've got the DayGui class up, we notice that you're trying to use dayPanel before you've initialised it. i.e. nowhere do you say dayPanel = new JPanel();. This resulted in a NullPointerException being thrown in your code, screwing up your normal course of exection. Fix this and your DayGui class would run fine at runtime.
Among your codebase, you also do some very funky things, namely start using something but never getting around to finishing it up. An example of this is you extending JPanel, but resorting to using a member variable of type JPanel to do the rest of the work. The suggestion is to scrap the instance variable all together and use the methods you've inherited from extending JPanel.
Now lets move onto your JTabbedPaneAssignment class. Although not terrible, the code is not very readable and it repeats itself in many places (adding your tabbedpanel multiple times). If you were to take this code further into a larger project, maintenance and debugging would quickly become a problem.
For the purposes of showing you how much clutter you had in your code, I've quickly rewritten your provided code to be compilable, and should roughly do what you're working on.
JTabbedPaneAssignment:
import java.awt.BorderLayout;
import java.awt.event.KeyEvent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTabbedPane;
import javax.swing.SwingUtilities;
public class JTabbedPaneAssignment extends JPanel
{
public JTabbedPaneAssignment()
{
final JTabbedPane tabbedPane = new JTabbedPane();
final DayPanel dayPanel = new DayPanel();
final JPanel officePanel = new JPanel();
tabbedPane.add("DayGui", dayPanel);
tabbedPane.setMnemonicAt(0, KeyEvent.VK_1);
tabbedPane.add("OfficeAreaCalculator", officePanel);
tabbedPane.setMnemonicAt(1, KeyEvent.VK_2);
add(tabbedPane);
}
// Create JTabbedPane
private static void createAndShowGUI()
{
// Create and set up the window.
JFrame frame = new JFrame("JTabbedPane");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new JTabbedPaneAssignment(), BorderLayout.CENTER);
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args)
{
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
createAndShowGUI();
}
});
}
}
DayGui - renamed as DayPanel:
import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
public class DayPanel extends JPanel {
public DayPanel() {
super();
setBackground(Color.CYAN);
final JButton goodButton = new JButton("Good");
final JButton badButton = new JButton("Bad");
ActionListener listener = new DayPanel.ButtonsHandler();
goodButton.addActionListener(listener);
badButton.addActionListener(listener);
add(goodButton);
add(badButton);
}
class ButtonsHandler implements ActionListener {
#Override
public void actionPerformed(ActionEvent e) {
final String command = ((JButton) e.getSource()).getActionCommand();
if (command.equals("Good")) {
showMessage("Today is a good day!");
} else if (command.equals("Bad")) {
showMessage("Today is a bad day!");
}
}
// Show popup message
private void showMessage(String message) {
JOptionPane.showMessageDialog(null, message,
"Event Handler Message", JOptionPane.INFORMATION_MESSAGE);
}
}
}
So what is different in these? Basically, I've removed your NullPointerException you were getting in DayGui. Any other changes I've made are with the intention than you try and keep your code clutter free, so you really know what is going on in your code.
Hope this helps.

When I run it, both JPanels open, but the JTabbedPane does not. I get
a lot of Unknown Source errors.
Well, based on your code and your import section:
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
This lines won't compile (unless DayGUI and OfficeAreaCalculator classes are in the same package than your JTabbedPaneAssignment class):
DayGui pnlDay = new DayGui();
OfficeAreaCalculator pnlOffice = new OfficeAreaCalculator ();
This is the only error I've got trying to compile and run your example. I changed lines below:
tabbedPane.addTab( "DayGui", new JPanel());
tabbedPane.addTab("Office Calculator", new JPanel());
And it worked like a charm.
Update
Based on your recent edit (adding your DayGui class, thank you) you have couple of mistakes in your code.
DayGui : this class extends of JPanel so you need to add your components directly on this class, you don't need this panel:
private JPanel dayPanel;
You need to set the layout manager, buttons and background directly on DayGuiclass, like this:
public DayGui() {
cmdGood = new JButton("Good");
cmdBad = new JButton("Bad");
setLayout(new FlowLayout());
add(cmdGood);
add(cmdBad);
setSize(300, 150);
ButtonsHandler bhandler = new ButtonsHandler();
cmdGood.addActionListener(bhandler);
cmdBad.addActionListener(bhandler);
setBackground(Color.CYAN);
}
JTabbedPaneAssignment : I think you're trying to add panel1 and panel2 as tabs but you use add method instead addTab:
JPanel panel1 = new JPanel();
JPanel panel2 = new JPanel();
tabbedPane.add(panel1,"First panel");
tabbedPane.add(panel2,"Second panel");
Also this line:
tabbedPane.addTab("DayGui", panel1);
Should be:
tabbedPane.addTab("DayGui", pnlDay);
Finally in this line you are adding panel2 for a second time and that's not correct:
tabbedPane.addTab("OfficeAreaCalculator", panel2); //I'd comment this line
If you make suggested changes you'll see something like this (BTW the CYAN color almost made me blind :P):
Hope this be helpful and sorry for the extension.