Develop Reference

Use a JButton to add new panels at runtime

I feel as beginner I may have bitten off too much in regards to application building. That said, I am working on developing an application for a friend that will have prompts where each JPanel will provide fields to create an object to be used later. What I would like to have happen is that when the panel loads, it displays one object creation panel and a button to dynamically add a new panel if the user wants to make multiples (the plus button would add the new panel).
I have drawn up something in paint to illustrate this:
By my very limited understanding, I can create a panel to hold these sub-panels, and then add a action listener to the '+' button to create new panels. The only way I could think to implement this is to create a constructor for the panel I want to add. Is this possible? Let me show you what I have:
package com.company;
import java.awt.*;
import javax.swing.*;
/**
* Created by Travis on 3/1/2015.
*/
public class MainSnakeGui extends JFrame{
protected int panelCount;
//row 1
JPanel row1 = new JPanel();
JLabel splitSnakeLabel = new JLabel("Create a Split Snake", JLabel.CENTER);
//row 2
JPanel row2 = new JPanel();
JButton addButton = new JButton("+");
public MainSnakeGui() {
super("Snake Channels");
setSize(550, 400);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
GridLayout layout = new GridLayout(5, 1, 10, 10);
setLayout(layout);
FlowLayout layout1 = new FlowLayout(FlowLayout.CENTER, 10, 10);
row1.setLayout(layout1);
row1.add(splitSnakeLabel);
add(row1);
GridLayout layout2 = new GridLayout(1, 2, 10, 10);
row2.setLayout(layout2);
row2.add(addButton);
MainSnakeConstructor snakePanel = new MainSnakeConstructor();
row2.add(snakePanel);
add(row2);
setVisible(true);
}
public static void setLookAndFeel () {
try {
UIManager.setLookAndFeel("com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel");
} catch (Exception e) {
}
}
public static void main(String[] arg) {
MainSnakeGui.setLookAndFeel();
MainSnakeGui frame = new MainSnakeGui();
}
}
Here is the constructor:
package com.company;
import javax.swing.*;
import java.awt.*;
/**
* Created by Travis on 3/1/2015.
*/
public class MainSnakeConstructor extends JFrame {
public MainSnakeConstructor () {
JPanel splitSnakeRow = new JPanel();
JLabel snakeNameLabel = new JLabel("Snake Name");
JLabel channelCountLabel = new JLabel("Channel Count");
JCheckBox artistSuppliedCheckBox = new JCheckBox("Artist Supplied?");
JTextField snakeNameTextField = new JTextField(30);
JTextField channelCountTextField = new JTextField(3);
GridLayout layout = new GridLayout(3,2,10,10);
splitSnakeRow.setLayout(layout);
splitSnakeRow.add(snakeNameLabel);
splitSnakeRow.add(channelCountLabel);
splitSnakeRow.add(artistSuppliedCheckBox);
splitSnakeRow.add(snakeNameTextField);
splitSnakeRow.add(channelCountTextField);
add(splitSnakeRow);
}
}

Think about it differently. You want a button that allows you to add new panels, so you really only need a single button.
From there, you need some kind common panel which provides the functionality you want to the user (the creation panel). Then, when the user clicks the add button, you create a new creation panel and add it to the container been used to display them, for example...
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.FlowLayout;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.border.CompoundBorder;
import javax.swing.border.EmptyBorder;
import javax.swing.border.LineBorder;
public class Test {
public static void main(String[] args) {
new Test();
}
public Test() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
public TestPane() {
JButton btnAdd = new JButton("+");
setLayout(new BorderLayout());
JPanel buttons = new JPanel(new FlowLayout(FlowLayout.LEFT));
buttons.add(btnAdd);
add(buttons, BorderLayout.NORTH);
JPanel content = new JPanel(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridwidth = GridBagConstraints.REMAINDER;
gbc.weighty = 1;
content.add(new JPanel(), gbc);
add(new JScrollPane(content));
btnAdd.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
CreationPane pane = new CreationPane();
int insertAt = Math.max(0, content.getComponentCount() - 1);
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridwidth = GridBagConstraints.REMAINDER;
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.weightx = 1;
content.add(pane, gbc, insertAt);
content.revalidate();
content.repaint();
}
});
}
#Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
}
public static class CreationPane extends JPanel {
private static int count;
public CreationPane() {
setLayout(new GridBagLayout());
add(new JLabel("Make it so " + (count++)));
setBorder(new CompoundBorder(new LineBorder(Color.BLACK), new EmptyBorder(10, 10, 10, 10)));
}
}
}
Now having done all that, I prefer the VerticalLayout manager from SwingLabs, SwingX library, which basically does the same thing...

GUI: JButton Covering almost the entire screen

I have encountered a problem whilst working the JFrame's, and JButtons. I am trying to center my JButton, however when I do so, it covers almost the entire screen. Any idea's on what's causing this?
Here is a picture on how it looks :
And here is my code :
package character;
import javax.imageio.ImageIO;
import javax.swing.*;
import java.awt.*;
import java.io.IOException;
/**
* Created by Niknea on 6/28/14.
*/
public class characterSelector{
JFrame cselectorButtons, clogo;
JLabel logo, characterName, label;
JButton male, female;
public characterSelector(){
this.createCharacterSelector();
}
public void createCharacterSelector() {
try {
label = new JLabel(new ImageIcon(ImageIO.read(getClass()
.getResource("/resources/Grass_Background.jpg"))));
cselectorButtons = new JFrame("SupremeSoccer");
logo = new JLabel(new ImageIcon(ImageIO.read(this.getClass().getResource("/resources/Character_Selector_Image.png"))));
characterName = new JLabel("<Character Name>");
characterName.setFont(new Font(characterName.getFont().getName(),
Font.HANGING_BASELINE, 50));
/*
Buttons
*/
male = new JButton("Male");
////******************////
//// END OF BUTTONS ////
////****************////
cselectorButtons.add(logo);
cselectorButtons.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
cselectorButtons.setContentPane(label);
cselectorButtons.setLayout(new BorderLayout());
cselectorButtons.add(logo, BorderLayout.NORTH);
cselectorButtons.add(male, BorderLayout.CENTER);
cselectorButtons.pack();
cselectorButtons.setLocationRelativeTo(null);
cselectorButtons.setVisible(true);
} catch (IOException exp) {
exp.printStackTrace();
}
}
}
Thanks again.

Any idea's on what's causing this?
This is the default behaviour of BorderLayout. The component at the CENTER position will occupy the maximum amount of space the is available from the parent component, when the other (NORTH, SOUTH, EAST, WEST) positions have been taken into account
Depending on what you are trying to achieve you might consider creating another JPanel (set it's opaque state to false so it's transparent) and use something like GridLayout or GridBagLayout instead.
Take a look at A Visual Guide to Layout Managers for some more ideas
Updated
So based on your linked code, I changed
part2 = new JPanel();
to
part2 = new JPanel(new java.awt.GridBagLayout());
And got...
Updated with additional example
Start by breaking down your requirements into individual containers and focus on the layout requirements for each individual, then build them all back into a single container.
This will make changing them later much easier and also make controlling them much easier...
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Font;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.image.BufferedImage;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class ExampleLayout {
public static void main(String[] args) {
new ExampleLayout();
}
public ExampleLayout() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private HeaderPane header;
private ScorePane score;
private CharacterSelectionPane characterSelection;
public TestPane() {
setLayout(new BorderLayout());
JLabel background = new JLabel();
try {
BufferedImage img = ImageIO.read(getClass().getResource("/Grass.jpg"));
background.setIcon(new ImageIcon(img));
} catch (IOException ex) {
ex.printStackTrace();
}
add(background);
background.setLayout(new GridBagLayout());
header = new HeaderPane();
score = new ScorePane();
characterSelection = new CharacterSelectionPane();
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridwidth = GridBagConstraints.REMAINDER;
gbc.weightx = 1;
gbc.fill = GridBagConstraints.BOTH;
background.add(header, gbc);
background.add(score, gbc);
gbc.weighty = 1;
background.add(characterSelection, gbc);
}
}
public class HeaderPane extends JPanel {
public HeaderPane() {
setLayout(new BorderLayout());
JLabel label = new JLabel("Character Selection");
label.setForeground(Color.WHITE);
label.setFont(label.getFont().deriveFont(Font.BOLD, 48f));
label.setHorizontalAlignment(JLabel.CENTER);
add(label);
setOpaque(false);
}
}
public class ScorePane extends JPanel {
public ScorePane() {
JLabel label = new JLabel("[-][-[]-][-]");
label.setForeground(Color.YELLOW);
add(label);
setOpaque(false);
}
}
public class CharacterSelectionPane extends JPanel {
private JButton btMale;
private JButton btFemale;
private JTextField tfName;
private JButton btContinue;
public CharacterSelectionPane() {
setOpaque(false);
setLayout(new GridBagLayout());
btMale = new JButton("Male");
btFemale = new JButton("Female");
btContinue = new JButton("Continue");
tfName = new JTextField(10);
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridx = 0;
gbc.gridy = 0;
gbc.insets = new Insets(4, 4, 4, 4);
gbc.fill = GridBagConstraints.HORIZONTAL;
add(btMale, gbc);
gbc.gridx++;
add(btFemale, gbc);
gbc.gridx = 0;
gbc.gridy++;
add(new JLabel("Name:"), gbc);
gbc.gridx++;
add(tfName, gbc);
gbc.gridx = 0;
gbc.gridy++;
gbc.gridwidth = GridBagConstraints.REMAINDER;
add(btContinue, gbc);
}
}
}

Use a BoxLayout or (easier) GridBagLayout for the bottom area, as seen in this answer.

How can I build 2 JButton instances of the same width

I have 2 buttons, one named btnShort and one named btnLong. I'd like them to be of the same width, so what would be the best option?
import java.awt.Dimension;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class TestCode2 {
public static void main(String[] args) {
JFrame window = new JFrame("Test2");
window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
window.setSize(400, 200);
// ---------------------------------------------------------------------
GridBagLayout layout = new GridBagLayout();
GridBagConstraints constraints = new GridBagConstraints();
JPanel container = new JPanel(layout);
window.add(container);
constraints.gridy = 0;
JButton btnShort = new JButton("Short");
layout.setConstraints(btnShort, constraints);
container.add(btnShort);
constraints.gridy = 1;
JButton btnLong = new JButton("That's a long button");
layout.setConstraints(btnLong, constraints);
container.add(btnLong);
//This one won't work because button dimension is not known yet...
//btnShort.setPreferredSize(new Dimension(btnLong.getWidth(), btnLong.getHeight()));
// ---------------------------------------------------------------------
window.setVisible(true);
}
}

Set the GridBagConstraints fill property to GridBagConstraints.HORIZONTAL so that both JButton components occupy equal width in the container
constraints.fill = GridBagConstraints.HORIZONTAL;

Make use of an appropriate layout manager, like GridBagLayout and it's constraints...
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class Buttons {
public static void main(String[] args) {
new Buttons();
}
public Buttons() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException ex) {
} catch (InstantiationException ex) {
} catch (IllegalAccessException ex) {
} catch (UnsupportedLookAndFeelException ex) {
}
JFrame frame = new JFrame("Test");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
public TestPane() {
setLayout(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridwidth = GridBagConstraints.REMAINDER;
gbc.fill = GridBagConstraints.HORIZONTAL;
add(new JButton("I'm a very long button"), gbc);
add(new JButton("I'm not"), gbc);
}
#Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
}
}

Is it possible to use a JSlider controlling multiple JTextfield?

I tried to use a JSlider to set text in three JTextFields.
My condition is the slider should work for textfield_1, only when a textfield_1 get its focus, similarly for the other two textfields.
When I tried to use the same slider with other textfield, only the first text field values getting changed.
Expecting valuable suggestions Thanks in Advance.
JSlider slider;
JTextField tf;
tf.addFocusListener(new FoucusListener(){
public void foucusGained(FocusEvent fe){
slider.addChangeListener(new ChangeListener()){
public void stateChanged(ChangeEvent ce){
JSlider slider =(JSlider)ce.getSource();
if(slider.getValueisAdjusting())
tf.setText(String.valueOf(slider.getValue()))
}
});
});

The basic idea is you need to know what field was last selected. The problem is, when you select the slider, it will fire a focus gained event...
The simplest idea would be to use a FocusListener registered only to the text fields and maintain a reference to the last field selected.
When the slider changes, you would simply interact with the last selected field (if it's not null)
import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.FocusAdapter;
import java.awt.event.FocusEvent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JSlider;
import javax.swing.JTextField;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
public class SliderControl {
public static void main(String[] args) {
new SliderControl();
}
public SliderControl() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private JSlider slider;
private JTextField[] fields;
private JTextField selectedField;
public TestPane() {
setLayout(new GridBagLayout());
fields = new JTextField[3];
FocusHandler focusHandler = new FocusHandler();
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridx = 0;
gbc.gridy = 0;
for (int index = 0; index < 3; index++) {
fields[index] = new JTextField(3);
fields[index].addFocusListener(focusHandler);
add(fields[index], gbc);
gbc.gridy++;
}
gbc.fill = GridBagConstraints.HORIZONTAL;
slider = new JSlider();
slider.addChangeListener(new ChangeListener() {
#Override
public void stateChanged(ChangeEvent e) {
if (selectedField != null) {
selectedField.setText(String.valueOf(slider.getValue()));
}
}
});
add(slider, gbc);
}
protected class FocusHandler extends FocusAdapter {
#Override
public void focusGained(FocusEvent e) {
if (e.getComponent() instanceof JTextField) {
selectedField = (JTextField) e.getComponent();
}
}
}
}
}

How to change size of JTextArea

I have three radio buttons that I want to use to change the size of a JTextArea when I click the buttons.
if(rd_7inch.isSelected())
{
jScrollPane2.setSize(200,200);
txt_sysnp.setSize(5,20);
}if(rd_9inch.isSelected())
{
jScrollPane2.setSize(200,200);
txt_sysnp.setSize(5,25);
}if(rd_10inch.isSelected())
{
jScrollPane2.setSize(200,200);
txt_sysnp.setSize(5,30);
}

The important point is that whenever you update the UI you have to call revalidate() on that panel or container so that your changes get apply.
You can also do this by setSize() method.
public void showDialog(){
btnUp.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
dimSPane.setSize(new Dimension(400,50));
pane.revalidate();
}
});
btnUp.setSize(new Dimension(100,24));
btnDn.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
dimSPane.setSize(new Dimension(200,25));
pane.revalidate();
}
});
btnDn.setSize(new Dimension(100,24));
dimSPane.setSize(new Dimension(200,25));
Dimension dimtfield = new Dimension();
dimtfield.setSize(new Dimension(200,25));
spane.setMinimumSize(dimSPane);
spane.setMaximumSize(dimSPane);
spane.setPreferredSize(dimSPane);
tfield.setMinimumSize(dimtfield);
tfield.setMaximumSize(dimtfield);
tfield.setPreferredSize(dimtfield);
pane.add(spane);
pane.add(tfield);
pane.add(btnUp);
pane.add(btnDn);
JDialog dlg =new JDialog();dlg.add(pane);
dlg.pack();
dlg.show();
}

It is likely that you components are under the control of a layout manager.
The only means by which you can suggest changes to the size would be to use setColumns and setRows and use a layout manager that respects the preferred size of its components
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import javax.swing.AbstractAction;
import javax.swing.ButtonGroup;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JRadioButton;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class TextAreaSize {
public static void main(String[] args) {
new TextAreaSize();
}
public TextAreaSize() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private JTextArea ta;
public TestPane() {
setLayout(new GridBagLayout());
JRadioButton btnSmall = new JRadioButton(new SizeAction("Small", 2, 10));
JRadioButton btnMed = new JRadioButton(new SizeAction("Medium", 4, 15));
JRadioButton btnLarge = new JRadioButton(new SizeAction("Large", 12, 24));
ButtonGroup bg = new ButtonGroup();
bg.add(btnSmall);
bg.add(btnMed);
bg.add(btnLarge);
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridx = 0;
gbc.gridy = 0;
gbc.anchor = GridBagConstraints.NORTHWEST;
add(btnSmall, gbc);
gbc.gridy++;
add(btnMed, gbc);
gbc.gridy++;
add(btnLarge, gbc);
gbc.gridx++;
gbc.gridy = 0;
gbc.gridheight = GridBagConstraints.REMAINDER;
gbc.anchor = GridBagConstraints.CENTER;
ta = new JTextArea();
add(new JScrollPane(ta), gbc);
btnSmall.doClick();
}
#Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
public class SizeAction extends AbstractAction {
private int rows;
private int columns;
public SizeAction(String name, int rows, int columns) {
putValue(NAME, name);
this.rows = rows;
this.columns = columns;
}
#Override
public void actionPerformed(ActionEvent e) {
ta.setRows(rows);
ta.setColumns(columns);
revalidate();
}
}
}
}