Develop Reference

Java game involving adjacent JButtons

I'm making a small game involving a grid of JButtons (MxN) and the main premise is to click on buttonA and then on buttonB, coloring buttonB and adjacent buttons of the same color as buttonB with the color of buttonA. I have made it so you are able to choose 3 possible difficulties. The colors are randomly generated. The main problem is getting the colors to change.
This is the method that I call after selecting the difficulty of the game:
public static void gameMechanics(int m, int n) {
final String[] pickedColour = {""};
final String[] placedColour = {""};
JButton[][] picked = new JButton[m][n];
JButton[][] placed = new JButton[m][n];
picked[m][n].addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
pickedColour[0] = picked[m][n].getText();
}
});
placed[m][n].addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
placedColour[0] = placed[m][n].getText();
}
});
if (pickedColour[0] == "R" && placedColour[0] != "R") {
placed[m][n].setBackground(Color.RED);
placed[m][n].setText("R");
}
else if (pickedColour[0] == "G" && placedColour[0] != "G") {
placed[m][n].setBackground(Color.GREEN);
placed[m][n].setText("G");
}
else if (pickedColour[0] == "B" && placedColour[0] != "B") {
placed[m][n].setBackground(Color.BLUE);
placed[m][n].setText("B");
}
}

I would consider using JPanels and painting them, using a MouseListener instead.
However, if you're set on using JButtons, try this:
button.setBackground(Color.GREEN);
button.setOpaque(true);
Note that this might not work if you're setting the look and feel using UIManager.
Also, you're doing a ton of extra work to map the color to the button - it could get confusing and cause errors down the road. Instead, you might try creating your own class:
class ColoredButton extends JButton {
private static final long serialVersionUID = 3040767030924461426L;
private Color color;
public ColoredButton(Color c) {
this.color = c;
this.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
changeColor();
}
});
}
public void changeColor() {
this.setBackground(this.color);
this.setOpaque(true);
}
}
Now, you can construct a new ColoredButton:
// Now, this button will turn green when clicked
ColoredButton temp = new ColoredButton(Color.GREEN);

java swing hold both mouse buttons

I want to implement a method where the user needs to hold the left and right mouse buttons at the same time.
I'm using Swing and Java 1.7. I've tried this, but it doesn't detect the both-buttons case like I'd expect it to:
public void mousePressed(MouseEvent e) {
if (SwingUtilities.isLeftMouseButton(e) && SwingUtilities.isRightMouseButton(e)){
///code here
}
}
i tried to separate methods and use bool values to decide if the mouse button is pressed and then i set a condition to find out if both of them are pressed at the same time , but that didint work out too ..

This is an SSCCE that does what you want... i.e. if I understood your question correctly.
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class StackOverflow15957076 extends MouseAdapter
{
private JLabel status;
private boolean isLeftPressed;
private boolean isRightPressed;
public StackOverflow15957076 ()
{
JFrame frame = new JFrame ();
frame.setDefaultCloseOperation (JFrame.DISPOSE_ON_CLOSE);
JPanel panel = new JPanel (new FlowLayout (FlowLayout.CENTER));
status = new JLabel ("waiting for both mouse buttons...");
status.addMouseListener (this);
panel.add (status);
frame.add (panel);
frame.pack ();
frame.setVisible (true);
isLeftPressed = false;
isRightPressed = false;
}
#Override
public void mousePressed (MouseEvent e)
{
if (SwingUtilities.isLeftMouseButton (e))
{
isLeftPressed = true;
}
else if (SwingUtilities.isRightMouseButton (e))
{
isRightPressed = true;
}
if (isLeftPressed && isRightPressed)
{
status.setText ("both buttons are pressed");
}
}
#Override
public void mouseReleased (MouseEvent e)
{
if (SwingUtilities.isLeftMouseButton (e))
{
isLeftPressed = false;
}
else if (SwingUtilities.isRightMouseButton (e))
{
isRightPressed = false;
}
status.setText ("waiting for both mouse buttons...");
}
public static void main (String[] args)
{
SwingUtilities.invokeLater (new Runnable ()
{
#Override
public void run ()
{
new StackOverflow15957076 ();
}
});
}
}

It seems that it's not possible do it directly, since mouse events are fired sequentially. See, for example, this SO question/answers.
So you will need to decide what "at the same time" actually means to you (i.e. how close in time thay should be). Then you can capture two separate events and compare their getWhen() values.

Trouble with RadioButtons and booleans connection

Well its weird. I am not good with radiobuttons by the way. But I made a JPanel program in netbeans which includes a RadioButton. You enter all this information with JTextFields(no problem) and then lastly I had a JButton which you click the choice you want. Then I have a JButton that takes all the information and outputs this. For the RadioButton, I first entered the usual:
family = new JRadioButton("Family", true);
friend = new JRadioButton("Friend");
relative = new JRadioButton("Relative");
friendFriend = new JRadioButton("Friend of Friend");
ButtonGroup group = new ButtonGroup();
group.add (friend);
group.add (family);
group.add (relative);
group.add (friendFriend);
(I'm not sure if I needed a listner for the RadioButtons or not but my program still seems to "crash" no matter what).
then I had one action listner for the JButton which included all the textfields and radio buttons. But the RadioButton is the issue.
In the action listner I had:
Object source = event.getSource();
if (source == family)
relation1 = true;
else
if (source == friend)
relation2 = true;
else
if(source == relative)
relation3 = true;
else
if(source == friendFriend)
relation4 = true;
Then I made a relation class:
public class Relation {
private boolean arrayFamily, arrayFriend, arrayRelative, arrayFriendFriend;
public Relation(boolean relation1, boolean relation2, boolean relation3,
boolean relation4)
{
this.arrayFamily = relation1;
this.arrayFriend = relation2;
this.arrayRelative = relation3;
this.arrayFriendFriend = relation4;
}
public String relations ()
{
String relationship = null;
if(arrayFamily && !arrayFriend && !arrayRelative && !arrayFriendFriend == true)
{
relationship = "Family";
}
else
if(arrayFriend && !arrayFamily && !arrayRelative &&
!arrayFriendFriend == true)
{
relationship = "Friend";
}
else
if(arrayRelative && !arrayFamily && !arrayFriend &&
!arrayFriendFriend == true)
{
relationship = "Relative";
}
else
if(arrayFriendFriend && !arrayFamily && !arrayFriend &&
!arrayRelative == true)
{
relationship = "Friend of a Friend";
}
return relationship;
}
}
LASTLY back in the action listner, I implementer this class:
Relation relationship = new Relation(relation1, relation2, relation3
, relation4);
String arrayRelation = relationship.relations();
I lastly included arrayRelation in an array but the array worked fine.
My problem is that the output of the array for my RadioButtons keeps reading "null" (most likey because this code: String relationship = null;). I assume this means that none of my if else statements were satisfied and I really dont know why.
Also important to point out is that if I click submit without clicking any radio button (the button stays on "family"), it reads null. If I click a button once it works perfectly reading the string I intended. But if I click another button afterwards and click submit again, the string goes back to "null".
I know its lengthy but I would really appreciate any help because I am lost.
P.S. some parts of my code are repetitive because I was playing around trying to fix the problem.

I suggest you handle your action events separately, for example:
family.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
familyActionPerformed(evt);
}
});
Then implement familyActionPerformed(evt):
private void familyActionPerformed(java.awt.event.ActionEvent evt) {
// every click on family radio button causes the code here to be executed
relation1 = true;
}
Also write an event handler for the button you click, like this:
submitButtonActionPerformed(java.awt.event.ActionEvent evt) {
// Here test the state of each radio button
relation1 = family.isSelected();
relation2 = friend.isSelected();
relation3 = relative.isSelected();
relation4 = friendFriend.isSelected();
}
MORE EDIT:
Doing what you're doing with NetBeans should be very easy. Here are tutorials that will clear it all up for you:
Tutorial 1
Tutorial 2
I explain the solution again:
Using 'family' button as an example, in your constructor where you have created and initialised your GUI components do this:
JRadioButton family = new JRadioButton();
// do any other thing you want to do to this button and finally..
family.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
familyActionPerformed(evt);
}
});
JButton submit = new JButton("Submit");
submit.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
submitActionPerformed(evt);
}
});
Then somewhere create these methods:
private void familyActionPerformed(java.awt.event.ActionEvent evt){
// each time family is selected, you code processes the lines below:
...
}
private void submiteActionPerformed(java.awt.event.ActionEvent evt){
relation1 = family.isSelected();
relation2 = friend.isSelected();
relation3 = relative.isSelected();
relation4 = friendFriend.isSelected();
}
Do something similar for the rest of the RadioButtons.

I think that you're making things way too complex for yourself. If all you want is the String of the JRadioButton pressed, then use the ButtonGroup to get it for you. It can return the ButtonModel of the selected JRadioButton (if any one was selected), and from that you can extract the actionCommand String, although you'll have to remember to set this when you create your JRadioButton.
For example:
import java.awt.event.ActionEvent;
import javax.swing.*;
#SuppressWarnings("serial")
public class JRadioExample extends JPanel {
private static final String[] RADIO_TITLES = { "Family", "Friend",
"Relative", "Friend or Relative" };
private ButtonGroup btnGrp = new ButtonGroup();
public JRadioExample() {
for (int i = 0; i < RADIO_TITLES.length; i++) {
JRadioButton rBtn = new JRadioButton(RADIO_TITLES[i]);
rBtn.setActionCommand(RADIO_TITLES[i]); // ***** this is what needs to
// be set
btnGrp.add(rBtn);
add(rBtn);
}
add(new JButton(new BtnAction("Get Chosen Selection")));
}
private class BtnAction extends AbstractAction {
public BtnAction(String name) {
super(name);
}
#Override
public void actionPerformed(ActionEvent evt) {
ButtonModel model = btnGrp.getSelection();
if (model != null) {
String actionCommand = model.getActionCommand();
System.out.println("Selected Button: " + actionCommand);
} else {
System.out.println("No Button Selected");
}
}
}
private static void createAndShowGui() {
JRadioExample mainPanel = new JRadioExample();
JFrame frame = new JFrame("JRadioExample");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}

JComboBox not showing arrow

I have been searching this site and google for a solution to my problem, and I can't find anything. I think it's supposed to just work; however, it doesn't. The arrow icon for my JComboBox doesn't show up, and I can't find anywhere to set its visibility to true.
Here's my code:
public class Driver implements ActionListener {
private JTextField userIDField;
private JTextField[] documentIDField;
private JComboBox repository, environment;
private JButton close, clear, submit;
private JFrame window;
public Driver()
{
window = makeWindow();
makeContents(window);
window.repaint();
}
private JFrame makeWindow()
{
JFrame window = new JFrame("");
window.setSize(500,300);
window.setLocation(50,50);
window.getContentPane().setLayout(null);
window.setResizable(false);
window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
window.setVisible(true);
return window;
}
private void makeContents(JFrame w)
{
makeDropDowns(w);
w.repaint();
}
private void makeDropDowns(JFrame w)
{
String[] repositoryArray = {"Click to select", "NSA", "Finance", "Test"};
repository = new JComboBox(repositoryArray);
repository.setSelectedIndex(0);
repository.addActionListener(this);
repository.setSize(150,20);
repository.setLocation(175,165);
repository.setEditable(false);
w.add(repository);
String[] environmentArray = {"Click to select", "Dev", "Test", "Qual"};
environment = new JComboBox(environmentArray);
environment.setSelectedIndex(0);
environment.addActionListener(this);
environment.setSize(150,20);
environment.setLocation(175,195);
//environment.setEditable(false);
w.add(environment,0);
}
public void actionPerformed(ActionEvent e)
{
String repositoryID = "null", environmentID = "null";
if (e.getSource() == repository)
{
repositoryID = (String)repository.getSelectedItem();
}
if(e.getSource() == environment)
{
environmentID = (String)environment.getSelectedItem();
}
}
}
Here's a link to a picture of the problem:
If anyone could help that would be awesome.

It doesn't appear to be the issue you were suffering from, but I found this post due to the same resulting issue of the arrow disappearing.
In my case it was due to me mistakenly using .removeAll() on the JComboBox rather than .removeAllItems() when I was attempting to empty and then reuse the JComboBox after a refresh of the data I was using. Just thought I'd include it as an answer in case someone else comes across this thread for similar reasons.

The code you show works, but it looks like you're fighting the enclosing container's default layout. Here, ComboTest is a JPanel which defaults to FlowLayout.
Addendum: In general, do not use absolute positioning, as shown in your update. I've changed the example to use GridLayout; comment out the setLayout() call to see the default, FlowLayout.
import java.awt.EventQueue;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JPanel;
/**
* #see https://stackoverflow.com/a/10824504/230513
*/
public class ComboTest extends JPanel {
private JComboBox repository = createCombo(new String[]{
"Click to select", "NSA", "Finance", "Test"});
private JComboBox environment = createCombo(new String[]{
"Click to select", "Dev", "Test", "Qual"});
public ComboTest() {
this.setLayout(new GridLayout(0, 1));
this.add(repository);
this.add(environment);
}
private JComboBox createCombo(String[] data) {
final JComboBox combo = new JComboBox(data);
combo.setSelectedIndex(1);
combo.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
System.out.println(e.getActionCommand()
+ ": " + combo.getSelectedItem().toString());
}
});
return combo;
}
private void display() {
JFrame f = new JFrame("ComboTest");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.add(this);
f.pack();
f.setLocationRelativeTo(null);
f.setVisible(true);
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
new ComboTest().display();
}
});
}
}

I had the same issue. I fixed it by revalidating and repainting the panel with the following code :
myPanel.revalidate();
myPanel.repaint();

Maybe a little late, but for those who are still looking for an easy and fail-safe way to use the JComboBox can use this:
public class FixedJComboBox<E>
extends JComboBox<E> {
// Copied constructors
public FixedJComboBox() {
super();
}
public FixedJComboBox(ComboBoxModel<E> aModel) {
super(aModel);
}
public FixedJComboBox(E[] items) {
super(items);
}
public FixedJComboBox(Vector<E> items) {
super(items);
}
#Override
public void setBounds(int x, int y, int width, int height) {
super.setBounds(x, y, width, height);
// The arrow is the first (and only) component
// that is added by default
Component[] comps = getComponents();
if (comps != null && comps.length >= 1) {
Component arrow = comps[0];
// 20 is the default width of the arrow (for me at least)
arrow.setSize(20, height);
arrow.setLocation(width - arrow.getWidth(), 0);
}
}
}
As described here, the bug is caused by incorrectly setting both the location and the size of the arrow to (0,0), followed by some repainting issues. By simply overriding the setBounds() function, the arrow is always corrected after the UI/layout manager has wrongly updated the arrow.
Also, since new components are added after the old ones (i.e. higher index), the arrow will always be at the first element in the array (assuming you don't remove and re-add the arrow).
The disadvantage is of this class is that the width of the arrow is now determined by a constant instead of the UI/layout manager.

JScrollPane scrolling with arrow keys

I've a JTextArea component inside JScrollPane and the text area is not editable. I would like to enable scrolling of the text area with up and down arrow keys (i.e. pressing the arrow keys will scroll the text area by one line). Any ideas how to achieve this?

Yes Key Bindings is the way to go, but you don't always need to create your own actions. Swing components come with default Actions that you can often reuse.
See Key Bindings for a complete list of these Actions.
Now that you know the Action name you can just bind it to a keyStroke:
JScrollBar vertical = scrollPane.getVerticalScrollBar();
InputMap im = vertical.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW);
im.put(KeyStroke.getKeyStroke("DOWN"), "positiveUnitIncrement");
im.put(KeyStroke.getKeyStroke("UP"), "negativeUnitIncrement");

If the JTextArea is non-editable and non-focuseable, it will not respond to the arrow keys. I'm not sure if there is a canonical way to get around this, but one way to make it respond is to set its key binding to respond to the up and down keys when the JTextArea is in the focusable window. An example of this is as follows:
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import javax.swing.*;
import javax.swing.text.JTextComponent;
#SuppressWarnings("serial")
public class TestScrollingArea extends JPanel {
private static final String UP = "Up";
private static final String DOWN = "Down";
private JTextArea area = new JTextArea(20, 40);
private JScrollPane scrollPane = new JScrollPane(area);
public TestScrollingArea() {
// make textarea non-editable and non-focusable
area.setEditable(false);
area.setFocusable(false);
area.setWrapStyleWord(true);
area.setLineWrap(true);
add(scrollPane);
// fill area with letters
for (int i = 0; i < 10; i++) {
for (int j = 0; j < 100; j++) {
area.append("abcdefg ");
}
}
// have JTextArea tell us how tall a line of text is.
int scrollableIncrement = area.getScrollableUnitIncrement(scrollPane.getVisibleRect(),
SwingConstants.VERTICAL, 1);
// add key bindings to the JTextArea
int condition = JTextComponent.WHEN_IN_FOCUSED_WINDOW;
InputMap inMap = area.getInputMap(condition);
ActionMap actMap = area.getActionMap();
inMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0), UP);
inMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0), DOWN);
actMap.put(UP, new UpDownAction(UP, scrollPane.getVerticalScrollBar().getModel(),
scrollableIncrement));
actMap.put(DOWN, new UpDownAction(DOWN, scrollPane.getVerticalScrollBar().getModel(),
scrollableIncrement));
}
// Action for our key binding to perform when bound event occurs
private class UpDownAction extends AbstractAction {
private BoundedRangeModel vScrollBarModel;
private int scrollableIncrement;
public UpDownAction(String name, BoundedRangeModel model, int scrollableIncrement) {
super(name);
this.vScrollBarModel = model;
this.scrollableIncrement = scrollableIncrement;
}
#Override
public void actionPerformed(ActionEvent ae) {
String name = getValue(AbstractAction.NAME).toString();
int value = vScrollBarModel.getValue();
if (name.equals(UP)) {
value -= scrollableIncrement;
vScrollBarModel.setValue(value);
} else if (name.equals(DOWN)) {
value += scrollableIncrement;
vScrollBarModel.setValue(value);
}
}
}
private static void createAndShowUI() {
JFrame frame = new JFrame("TestScrollingArea");
frame.getContentPane().add(new TestScrollingArea());
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
createAndShowUI();
}
});
}
}

Just came across this problem and while the answers was useful in driving me to the right direction some bits of the solution may have changed since then. It worked for me with he following changes:
- it was the InputMap of JScrollPane instance that had to be changed
- actionMapKeys had to be: "unitScrollX" and/or "scrollX" (X= Down, Up, Left, Right). They reside in BasicScrollPaneUI.

You should add KeyListener to your JScrollPane.

All I had to do was to make the scroll pane request focus on mouse enter (as explained in this answer).
var scrollPane = new JScrollBar(jPanelCanvas);
scrollPane.addMouseListener(new MouseAdapter() {
#Override
public void mouseEntered(MouseEvent e) {
// this seems to enable key navigation
if ((e.getComponent() instanceof JScrollPane)) {
e.getComponent().requestFocus();
}
}
});
However I'm not sure on how to tweak the actions of these keys. Maybe by tweaking the actions on the JScrollPane directly as mentioned by tinca's answer.
The call to scrollPane.getActionMap() are showing the following actions defined
"unitScrollRight" -> {BasicScrollPaneUI$Actions#4310}
"unitScrollDown" -> {BasicScrollPaneUI$Actions#4312}
"scrollDown" -> {BasicScrollPaneUI$Actions#4314}
"scrollHome" -> {BasicScrollPaneUI$Actions#4316}
"scrollRight" -> {BasicScrollPaneUI$Actions#4318}
"scrollUp" -> {BasicScrollPaneUI$Actions#4320}
"unitScrollLeft" -> {BasicScrollPaneUI$Actions#4322}
"unitScrollUp" -> {BasicScrollPaneUI$Actions#4324}
"scrollEnd" -> {BasicScrollPaneUI$Actions#4326}
"scrollLeft" -> {BasicScrollPaneUI$Actions#4328}