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Java - Adding Arrays of JTextField and JLabel to a JPanel

I'm hoping this is an easy question. I have a JComboBox with the choices of 0, 1, 2, 3,...10. Depending on what number is selected in the JComboBox, I want my GUI to add a JLabel and a JTextField. So if the number 3 is chosen, the GUI should add 3 JLabels and 3 JTextFields. and so forth.
I'm using an array of JLabels and JTextFields to accomplish this, but I am getting a null pointer exception at runtime, and no labels or fields are being added.
Code:
private void createComponents()
{
//Create Action Listeners
ActionListener comboListener = new ComboListener();
//Create Components of the GUI
parseButton = new JButton("Parse Files");
parseButton.addActionListener(comboListener);
numberLabel = new JLabel("Number of Files to Parse: ");
String[] comboStrings = { "","1", "2","3","4","5","6","7","8","9","10" };
inputBox = new JComboBox(comboStrings);
inputBox.setSelectedIndex(0);
fieldPanel = new JPanel();
fieldPanel.setLayout(new GridLayout(2,10));
centerPanel = new JPanel();
centerPanel.add(numberLabel);
centerPanel.add(inputBox);
totalGUI = new JPanel();
totalGUI.setLayout(new BorderLayout());
totalGUI.add(parseButton, BorderLayout.SOUTH);
totalGUI.add(centerPanel, BorderLayout.CENTER);
add(totalGUI);
}
ActionListener Code:
public void actionPerformed(ActionEvent e)
{
JTextField[] fileField = new JTextField[inputBox.getSelectedIndex()];
JLabel[] fieldLabel = new JLabel[inputBox.getSelectedIndex()];
for(int i = 0; i < fileField.length; i++)
{
fieldLabel[i].setText("File "+i+":"); //NULL POINTER EXCEPTION HERE
fieldPanel.add(fieldLabel[i]); //NULL POINTER EXCEPTION HERE
fieldPanel.add(fileField[i]);
}
centerPanel.add(fieldPanel);
repaint();
revalidate();
}

Thanks to MadProgrammer's comment, this question has been answered.
Editing the loop to:
for(int i = 0; i < fileField.length; i++)
{
fieldLabel[i] = new JLabel();
fileField[i] = new JTextField();
fieldLabel[i].setText("File "+i+":");
fieldPanel.add(fieldLabel[i]);
fieldPanel.add(fileField[i]);
}
resolved the issue.

ScrollPane adding to grid layout

in my code I am calling a few items(my buttons with their names leading to different project. The names and everything are taken from a database)
I want a J ScrollPane to surround my buttons, what can I do? I just want the buttons to be called inside the scroll pane. Here is my code
import java.sql.*;
import java.util.ArrayList;
import java.util.List;
import java.awt.GridLayout;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JLabel;
import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
public class AdminClass implements ActionListener {
ProjectButton[] buttons = new ProjectButton[35];
//Creating data field for unique Ids in the form of array list
ArrayList<Integer> uniqueIDList = new ArrayList<Integer>();
String[] projectNames;
int[] uniqueIds;
Connection conn1 = null;
Statement stmt1 = null;
JFrame frame = new JFrame("Admin Panel");
private JPanel panel = new JPanel();
JButton btnNewButton = new JButton("Add New Project");
public AdminClass() {
panel.setLayout(new GridLayout(10, 1));
panel.add(new JLabel("Welcome to Admin Panel"));
btnNewButton.addActionListener(this);
panel.add(btnNewButton);
panel.add(new JLabel("Existing Projects"));
conn1 = sqliteConnection.dbConnector();
try{
Class.forName("org.sqlite.JDBC");
conn1.setAutoCommit(false);
stmt1 = conn1.createStatement();
ResultSet rs1 = stmt1.executeQuery( "SELECT * FROM Project;" );
List<String> projectNameList = new ArrayList<String>();
while ( rs1.next() ){
int id = rs1.getInt("uniqueid");
String projectName = rs1.getString("name");
projectNameList.add(projectName);
uniqueIDList.add(id);
}
// Converting array list to array
projectNames = new String[projectNameList.size()];
projectNameList.toArray(projectNames);
uniqueIds = convertIntegers(uniqueIDList);
rs1.close();
stmt1.close();
conn1.close();
}
catch ( Exception e1 ) {
JOptionPane.showMessageDialog(null, e1);
}
// Adding buttons to the project
try{
for (int i = 0; i < projectNames.length; i++){
buttons[i] = new ProjectButton(projectNames[i]);
buttons[i].setId(uniqueIds[i]);
panel.add(buttons[i]);
buttons[i].addActionListener(this);
}
}
catch (Exception e2){
JOptionPane.showMessageDialog(null, e2);
}
frame.add(panel);
frame.setVisible(true);
frame.setSize(500, 500);
}
public void actionPerformed(ActionEvent e) {
for (int j = 0; j < buttons.length; j ++){
if (e.getSource() == buttons[j]){
AdminStatus sc = new AdminStatus(buttons[j].getId());
frame.dispose();
}
}
if (e.getSource() == btnNewButton){
frame.dispose();
WindowProjectAdmin wpa = new WindowProjectAdmin();
}
}
//Method to convert integar array list to integar array
public int[] convertIntegers(List<Integer> integers)
{
int[] ret = new int[integers.size()];
for (int i=0; i < ret.length; i++)
{
ret[i] = integers.get(i).intValue();
}
return ret;
}
}
This may seem very normal but it's really not, for some reason they are not visible or are not called inside a scroller. Please edit my code maybe?

Start by adding the buttons to their own container, this way you can control the layout of the buttons separately from the rest of the UI
JPanel panelFullOfButtons = new JPanel();
try {
for (int i = 0; i < projectNames.length; i++) {
buttons[i] = new ProjectButton(projectNames[i]);
buttons[i].setId(uniqueIds[i]);
panelFullOfButtons.add(buttons[i]);
buttons[i].addActionListener(this);
}
} catch (Exception e2) {
JOptionPane.showMessageDialog(null, e2);
}
Then add the "main" panel to the NORTH position of the frame and the "buttons" panel to the CENTER
frame.add(panel, BorderLayout.NORTH);
frame.add(new JScrollPane(panelFullOfButtons), BorderLayout.CENTER);
Mind you, in this case, I'd be very tempted to use something like a JList instead. See How to Use Lists for more details
I have done the same, can you tell me what's wrong?
// Problem #1...
JScrollPane pane = new JScrollPane();
pane.add(buttonPanel);
//...
// Problem #2...
panel.add(pane);
frame.add(panel);
These are competing with each other, moving the content around and overlapping with existing content...
public AdminClass() {
panel.setLayout(new GridLayout(3, 1));
panel.add(new JLabel("Welcome to Admin Panel"));
btnNewButton.addActionListener(this);
panel.add(btnNewButton);
panel.add(new JLabel("Existing Projects"));
List<String> projectNameList = new ArrayList<String>();
for (int index = 0; index < 1000; index++) {
projectNameList.add("Project " + index);
}
projectNames = projectNameList.toArray(new String[0]);
// Adding buttons to the project
buttons = new JButton[projectNameList.size()];
try {
for (int i = 0; i < projectNames.length; i++) {
buttons[i] = new JButton(projectNames[i]);
btnPnl1.add(buttons[i]);
buttons[i].addActionListener(this);
}
} catch (Exception e2) {
JOptionPane.showMessageDialog(null, e2);
}
frame.add(panel, BorderLayout.NORTH);
frame.add(new JScrollPane(btnPnl1), BorderLayout.CENTER);
frame.setVisible(true);
frame.setSize(500, 500);
}
In this case I'd prefer to use either a JList to show the projects or a WrapLayout for laying out the buttons

Its useless to create a GridLayout like this: panel.setLayout(new GridLayout(10, 1));. If you declare the rows as a non zero value, the column count will be ignored. When you declare the maximum number of rows as ten, you force the eleventh component to be added in a second column (then a third, a forth and so on). Use panel.setLayout(new GridLayout(0, 1)); instead to force the only one column and frame.add(new JScrollPane(panel)); to create the ScrollPane.
But note that GridLayout will try to shrink your components the maximum as possible to fit the container size before scrolling is enabled.

I just want the button part to be inside J Scroll Pane
If you just want the JButton's (those added within the loop):
Create a new JPanel that you add the buttons to
Add (1) to a JScrollPane
Add (2) to panel
For example:
JPanel buttonPanel = new JPanel(new FlowLayout());
for (int i = 0; i < projectNames.length; i++){
buttons[i] = new ProjectButton(projectNames[i]);
buttons[i].setId(uniqueIds[i]);
panel.add(buttons[i]);
buttonPanel[i].addActionListener(this);
}
JScrollPane scroller = new JScrollPane(buttonPanel);
panel.add(scroller);
You might also consider using a different Component that doesn't require a JScrollPane, of course depending upon your needs - for instance a JComboBox.

Split labels in JTabbedPane

I need to change my label's distribution on a JTabbedPane.
I have this:
And I want to do this:
Can someone help me?
I post the code below:
tabbedResultsPane = new JTabbedPane(SwingConstants.TOP);
JPanel featurePanel = new JPanel(new GridLayout(TOTAL_FEATURES, 2, 3, 3));
estadoScroll = new JScrollPane(featurePanel,
JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,
JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
lblFeatureHdr = new JLabel[TOTAL_FEATURES];
lblFeature = new JLabel[TOTAL_FEATURES];
for(int i=0; i<TOTAL_FEATURES; i++)
{
lblFeatureHdr[i] = new JLabel(strHeader[i], JLabel.RIGHT);
lblFeatureHdr[i].setOpaque(true);
lblFeatureHdr[i].setBackground(new Color(220,255,220));//.lightGray);
lblFeature[i] = new JLabel("", JLabel.LEFT);
lblFeature[i].setForeground(Color.blue);// black);
featurePanel.add(lblFeatureHdr[i]);
featurePanel.add(lblFeature[i]);
}

Define 4 columns GridLayout (rather than 2 columns you have).
and correct your code yo add 2 more labels for each row.
for(int i=0; i<TOTAL_FEATURES; i++)
{
lblFeatureHdr[i] = new JLabel(strHeader[i], JLabel.RIGHT);
lblFeatureHdr[i].setOpaque(true);
lblFeatureHdr[i].setBackground(new Color(220,255,220));//.lightGray);
lblFeature[i] = new JLabel("", JLabel.LEFT);
lblFeature[i].setForeground(Color.blue);// black);
featurePanel.add(lblFeatureHdr[i]);
featurePanel.add(lblFeature[i]);
// add 2 more lables to the same row
JLabel l=new JLabel(strHeader[i], JLabel.RIGHT);
l.setBackground(new Color(220,255,220));//.lightGray);
featurePanel.add(l);
featurePanel.add(new JLabel("", JLabel.LEFT));
}

JComboBox[] loop to show on JApplet not working

public class NewAccountApplet extends JApplet implements ActionListener{
JPanel jp1, jp2, jp3, jp4, jp5, jp6;
GridLayout productLO = new GridLayout(10,4,10,10);
int qty = 5;
JComboBox<Object>[] selectQty;
if (e.getActionCommand().equals("Login")) {
if (id.equals(checkID) && pw.equals(checkPW)) {
JOptionPane.showMessageDialog(null, "Authenticated");
JPanel content = (JPanel)getContentPane();
GridBagConstraints firstCol = new GridBagConstraints();
firstCol.weightx = 1.0;
firstCol.anchor = GridBagConstraints.WEST;
firstCol.insets = new Insets(5, 20, 5, 5);
GridBagConstraints lastCol = new GridBagConstraints();
lastCol.gridwidth = GridBagConstraints.REMAINDER;
lastCol.weightx = 1.0;
lastCol.fill = GridBagConstraints.HORIZONTAL;
lastCol.insets = new Insets(5, 5, 5, 20);
selectQty = new JComboBox[qty];
jp1.setVisible(false);
jp2.setVisible(false);
jp3.setVisible(false);
jp4.setVisible(true);
jp5.setVisible(true);
jp6.setVisible(true);
String[] itemText = {"1", "2", "3", "4", "5"};
JLabel[] items = new JLabel[6];
JLabel purchasePage = new JLabel("Items for Purchase");
jp4.add(purchasePage);
content.setLayout(new BoxLayout(content, BoxLayout.Y_AXIS));
content.add(jp4);
jp4 = new JPanel();
jp5 = new JPanel(new GridBagLayout()); //set jp5 as a new jpanel with gridbaglayout
jp6 = new JPanel();
for(int i=0; (i<items.length); i++) {
items[i] = new JLabel(); //adds items[i] as JLabel
items[i].setText(itemText[i]); //sets text of items as itemText[]
jp5.add(items[i], firstCol); //adds items to firstcol of jp5
selectQty[i] = new JComboBox<Object>(); //JComboBox selectqty[i]
selectQty[i].setPreferredSize(new Dimension(300, 20)); //sets the size
jp5.add(selectQty[i], lastCol); //sadsdasd
}
}
else JOptionPane.showMessageDialog(null, "Wrong account information");}
I have some questions regarding adding a JComboBox into a loop to display on my JApplet.
the for loop on the bottom adds my JComboBox (selectQty) to the screen. But I get an error message on eclipse where i coded as: items[i].setText(itemText[i]);.
It shows up my JPanel jp4 correctly. but the JPanel jp5 is not showing up.. I wonder what is wrong...
So to summarize, the code compiles (with other codes that are not on here), but japplet only shows jp4 jpanel, and error occrs on line: items[i].setText(itemText[i]);.

itemText has 5 elements {"1", "2", "3", "4", "5"} but JLabel[] items = new JLabel[6] items has 6.

You appear to be re-creating jp5 but neither removing the old instance or adding the new instance...
// This suggests that jp5 has already been created
jp5.setVisible(true);
//...
// But you create a new instance here
jp5 = new JPanel(new GridBagLayout());
// Then add stuff to it...
Try using jp5.removeAll() instead of jp5 = new JPanel(new GridBagLayout());
The likely cause of your error is probably IndexOutOfBoundsException caused by the fact the itemText and items have different numbers of elements
String[] itemText = {"1", "2", "3", "4", "5"};
JLabel[] items = new JLabel[6];
//...
for(int i=0; (i<items.length); i++) {
items[i] = new JLabel(); //adds items[i] as JLabel
// Error here on the last element...
items[i].setText(itemText[i]); //sets text of items as itemText[]
Instead, consider using something like...
String[] itemText = {"1", "2", "3", "4", "5"};
JLabel[] items = new JLabel[itemText.length];
And remember, magic numbers are a bad idea

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.logging.*;
public class NewAccountApplet extends JApplet implements ActionListener{
/**
*
*/
private static final long serialVersionUID = 1L;
JLabel titlePage;
JLabel[] txt;
JTextField[] jtf;
JButton accept, decline;
JPanel jp1, jp2, jp3, jp4, jp5, jp6;
String[] accountlist = {"Select Account Type.", "Customer", "Admin"};
JComboBox<Object> textAlignment = new JComboBox<Object>(accountlist);
GridLayout productLO = new GridLayout(10,4,10,10);
int qty = 5;
JComboBox<Object>[] selectQty;
public void init(){
setSize(400,400);
JPanel content = (JPanel)getContentPane();
GridBagConstraints firstCol = new GridBagConstraints();
firstCol.weightx = 1.0;
firstCol.anchor = GridBagConstraints.WEST;
firstCol.insets = new Insets(5, 20, 5, 5);
GridBagConstraints lastCol = new GridBagConstraints();
lastCol.gridwidth = GridBagConstraints.REMAINDER;
lastCol.weightx = 1.0;
lastCol.fill = GridBagConstraints.HORIZONTAL;
lastCol.insets = new Insets(5, 5, 5, 20);
String[] labeltxt = {"Name","Account ID","Password","E-Mail","Phone","Address","","","Account Type"};
titlePage = new JLabel("Create New Account");
txt = new JLabel[9];
jtf = new JTextField[9];
accept = new JButton("Create");
decline = new JButton("Decline");
jp1 = new JPanel();
jp2 = new JPanel(new GridBagLayout());
jp3 = new JPanel();
jp4 = new JPanel();
jp5 = new JPanel();
jp6 = new JPanel();
for(int i=0; (i<9); i++) {
txt[i] = new JLabel();
txt[i].setText(labeltxt[i]);
jp2.add(txt[i], firstCol);
jtf[i] = new JTextField();
jtf[i].setPreferredSize(new Dimension(300, 20));
jp2.add(jtf[i], lastCol);
}
jp1.add(titlePage);
jp3.add(accept);
jp3.add(decline);
content.setLayout(new BoxLayout(content, BoxLayout.Y_AXIS));
content.add(jp1);
content.add(jp2);
content.add(jp3);
String id = this.jtf[1].getText();
String pw = this.jtf[2].getText();
jtf[6].setText(id);
jtf[7].setText(pw);
jtf[6].setVisible(false);
jtf[7].setVisible(false);
jtf[8].setVisible(false);
jp2.add(textAlignment, lastCol);
decline.addActionListener(this);
accept.addActionListener(this);
}
public void actionPerformed(ActionEvent e) {
String id = jtf[1].getText();
String pw = jtf[2].getText();
String checkID = jtf[6].getText();
String checkPW = jtf[7].getText();
String accountType = "";
String correctType = "Customer";
String chosenType = (String) textAlignment.getSelectedItem();
JPasswordField pField = new JPasswordField(10);
JPanel pPanel = new JPanel();
pPanel.add(new JLabel("Please Enter Password: "));
pPanel.add(pField);
if (e.getActionCommand().equals("Create") && (chosenType.equals("Customer"))){
JOptionPane.showMessageDialog(null, "Thank you for Joining!");
id = jtf[1].getText();
pw = jtf[2].getText();
titlePage.setText("Welcome to Final Sales!");
accept.setText("Login");
decline.setText("Cancel");
txt[6].setText("UserName");
txt[7].setText("Password");
jtf[0].setText("");
jtf[3].setText("");
jtf[4].setText("");
jtf[5].setText("");
txt[0].setVisible(false);
txt[1].setVisible(false);
txt[2].setVisible(false);
txt[3].setVisible(false);
txt[4].setVisible(false);
txt[5].setVisible(false);
textAlignment.setVisible(false);
txt[8].setVisible(false);
jtf[0].setVisible(false);
jtf[1].setVisible(false);
jtf[2].setVisible(false);
jtf[3].setVisible(false);
jtf[4].setVisible(false);
jtf[5].setVisible(false);
jtf[6].setVisible(true);
jtf[7].setVisible(true);
}
if (e.getActionCommand().equals("Create") && (chosenType.equals("Admin"))) {
JOptionPane.showMessageDialog(null, pPanel);
JOptionPane.showMessageDialog(null, "Wrong Admin Password");
}
if (e.getActionCommand().equals("Create") && (chosenType.equals("Select Account Type."))) {
JOptionPane.showMessageDialog(null, "You have selected wrong account type.");
}
if (e.getActionCommand().equals("Decline"))
System.exit(0);
if (e.getActionCommand().equals("Login")) {
if (id.equals(checkID) && pw.equals(checkPW)) {
JOptionPane.showMessageDialog(null, "Authenticated");
JPanel content = (JPanel)getContentPane();
GridBagConstraints firstCol = new GridBagConstraints();
firstCol.weightx = 1.0;
firstCol.anchor = GridBagConstraints.WEST;
firstCol.insets = new Insets(5, 20, 5, 5);
GridBagConstraints lastCol = new GridBagConstraints();
lastCol.gridwidth = GridBagConstraints.REMAINDER;
lastCol.weightx = 1.0;
lastCol.fill = GridBagConstraints.HORIZONTAL;
lastCol.insets = new Insets(5, 5, 5, 20);
selectQty = new JComboBox[qty];
jp1.setVisible(false);
jp2.setVisible(false);
jp3.setVisible(false);
jp4.setVisible(true);
jp5.setVisible(true);
jp6.setVisible(true);
String[] itemText = {"White Snapback", "Silver Necklace", "Black T Shirt", "", "5"};
JLabel[] items = new JLabel[5];
JLabel purchasePage = new JLabel("Items for Purchase");
jp4.add(purchasePage);
content.setLayout(new BoxLayout(content, BoxLayout.Y_AXIS));
content.add(jp4);
jp4 = new JPanel();
jp5.setLayout(new GridBagLayout());
jp6 = new JPanel();
for(int i=0; (i<items.length); i++) {
items[i] = new JLabel();
items[i].setText(itemText[i]);
jp5.add(items[i], firstCol);
selectQty[i] = new JComboBox<Object>();
selectQty[i].setPreferredSize(new Dimension(300, 20));
jp5.add(selectQty[i], lastCol);
}
}
else JOptionPane.showMessageDialog(null, "Wrong account information");}
if (e.getActionCommand().equals("Cancel")) {
System.exit(0);}
}
}

Swing sample form application

I have come up with the below code:
String[] labels = {"Name: ", "Fax: ", "Email: ", "Address: "};
int numPairs = labels.length;
JFrame frame = new JFrame("SpringDemo1");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//Set up the content pane.
Container contentPane = frame.getContentPane();
SpringLayout layout = new SpringLayout();
contentPane.setLayout(layout);
for (int i = 0; i < numPairs; i++)
{
JLabel lable = new JLabel(labels[i]);
contentPane.add(lable);
contentPane.add(new JTextField(15));
}
//Display the window.
frame.pack();
frame.setVisible(true);
Expectation:
What I am getting:
Default:
when resized:
The result is noway related to how code actually/normally looks like!
I also tried copy pasting and running the ready-made code: downloaded from here:
and this is how the result looks :

To put the components in the right place using SpringLayout, you should use the ( SpringUtilities class ), download it then include it in your project.
your code should be:
private static void createAndShowGUI() {
String[] labels = {"Name: ", "Fax: ", "Email: ", "Address: "};
int numPairs = labels.length;
//Create and populate the panel.
JPanel p = new JPanel(new SpringLayout());
for (int i = 0; i < numPairs; i++) {
JLabel l = new JLabel(labels[i], JLabel.TRAILING);
p.add(l);
JTextField textField = new JTextField(10);
l.setLabelFor(textField);
p.add(textField);
}
//Lay out the panel.
SpringUtilities.makeCompactGrid(p,
numPairs, 2, //rows, cols
6, 6, //initX, initY
6, 6); //xPad, yPad
//Create and set up the window.
JFrame frame = new JFrame("SpringForm");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//Set up the content pane.
p.setOpaque(true); //content panes must be opaque
frame.setContentPane(p);
//Display the window.
frame.pack();
frame.setVisible(true);
}
i hope that helps you!