I need to use a JCombo box and at the moment I am just printing messages to screen for testing. When I make a selection it works as expected, however when I then re-click the combo box to change selection I get the same message box before it lets me make another selection. How would I get it so that the action is only performed on initial selection?
String[] positions={"1","2","3","4"};
JComboBox combo = new JComboBox<String>(positions);
combo.addActionListener(new ActionListener(){
#Override
public void actionPerformed(ActionEvent ae ){
//Display selected stuff
JOptionPane.showMessageDialog(null, combo.getSelectedItem());
}
});
Use a boolean to know if it has already been checked or not.
Solution
String[] positions={"1","2","3","4"};
JComboBox combo = new JComboBox<String>(positions);
combo.addActionListener(new ActionListener(){
boolean comboAlreadyChecked = false;
#Override
public void actionPerformed(ActionEvent ae ){
//Display selected stuff
if (!comboAlreadyChecked){
JOptionPane.showMessageDialog(null, combo.getSelectedItem());
comboAlreadyChecked = true;
}
}
});
PS : The name of your boolean may be a little easier than this one. This is just to clarify.
After taking onboard the answers provided and through modifying the solution given in the aforementioned tutorial, I came up with the following solution:
String labels[] = {"", "A", "B", "C", "D", "E", "F"};
JComboBox comboBox = new JComboBox(labels);
ItemListener itemListener = new ItemListener() {
public void itemStateChanged(ItemEvent itemEvent) {
int state = itemEvent.getStateChange();
ItemSelectable is = itemEvent.getItemSelectable();
if (selectedString(is) == "A" & state == ItemEvent.SELECTED) {
System.out.println("A");
}
}
};
comboBox.addItemListener(itemListener);
Please try this
public static void main(String args[]) {
JComboBox comboBox = new JComboBox();
comboBox.addItemListener(new ItemListener() {
#Override
public void itemStateChanged(ItemEvent e) {
System.err.println("new item: " + e.getItem());
}
});
}
I have a JComboBox that is editable. I need to fire event only following situations
user press enter while typing (this can be achieved adding key event listener) OR
user select item from list
in the following code, event fires while user typing in the editor as well,How can i avoid event firing while user typing?
comboForward.addItemListener(new ItemListener() {
public void itemStateChanged(ItemEvent e) {
if (e.getStateChange() == ItemEvent.SELECTED) {
new Thread() {
#Override
public void run() {
// code after the event.
}
}.start();
}
}
});
I think this is suitable for you. try it.
JFrame frame = new JFrame("Welcome!!");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JComboBox cmb = new JComboBox();
cmb.setEditable(true);
cmb.getEditor().getEditorComponent().addKeyListener(new KeyAdapter() {
#Override
public void keyReleased(KeyEvent event) {
if (event.getKeyChar() == KeyEvent.VK_ENTER) {
if (((JTextComponent) ((JComboBox) ((Component) event
.getSource()).getParent()).getEditor()
.getEditorComponent()).getText().isEmpty())
System.out.println("please dont make me blank");
}
}
});
frame.add(cmb);
frame.setLocationRelativeTo(null);
frame.setSize(300, 50);
frame.setVisible(true);
refer here :https://docs.oracle.com/javase/tutorial/uiswing/components/combobox.html
I have the following piece of code to create a JList:
rightPanel.add(Box.createRigidArea(new Dimension(20, 20)));
final JList list = new JList(nameData);
list.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
list.setLayoutOrientation(JList.VERTICAL);
list.setVisibleRowCount(5);
JScrollPane listScroller = new JScrollPane(list);
listScroller.setPreferredSize(new Dimension(250, 80));
listScroller.setAlignmentX(LEFT_ALIGNMENT);
rightPanel.add(listScroller);
And I have this code for a listSelectionListener() to disable a button, when an item in the list isn't selected:
list.addListSelectionListener(new ListSelectionListener() {
public void valueChanged(ListSelectionEvent e) {
if (e.getValueIsAdjusting() == false) {
if (list.getSelectedIndex() == -1) {
//No selection.
deleteConfirmButton.setEnabled(false);
} else {
//Selection.
deleteConfirmButton.setEnabled(true);
index = list.getSelectedIndex();
}
}
}
});
But whether an item in the list is selected or not, the state for the button doesn't change. What should I do?
Your deleteConfirmButton disable-enable logic is not correct. At first you need to disable. At the selection of list you should enable and at the click on deleteConfirmButton button you shoudl again disable. Read the comment of following code.
final JButton deleteConfirmButton = new JButton("Kustuta");
deleteConfirmButton.setEnabled(false); //Disable here
deleteConfirmButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
deleteConfirmButton.setEnabled(false);//Disable here
}
});
list.addListSelectionListener(new ListSelectionListener() {
public void valueChanged(ListSelectionEvent e) {
deleteConfirmButton.setEnabled(true);//Enable here
}
});
Assuming deleteConfirmButton is inside a JPanel named rightPanel, call the repaint and revalidate methods to paint the button again.
if (list.getSelectedIndex() == -1) {
//No selection.
deleteConfirmButton.setEnabled(false);
} else {
//Selection.
deleteConfirmButton.setEnabled(true);
index = list.getSelectedIndex();
}
rightPanel.repaint();
rightPanel.revalidate();
My code is quite simple actually. I saw a simple and similar code was from this article.
At first, I have 1 combobox. I have a listener on it called itemStateChanged(). My purpose to add into this listener is that; "to execute some code when user click (select) an item from its dropbox".
Cmb_ItemCategory = new javax.swing.JComboBox();
Cmb_ItemCategory.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "Loading..." }));
Cmb_ItemCategory.addItemListener(new java.awt.event.ItemListener() {
public void itemStateChanged(java.awt.event.ItemEvent evt) {
Cmb_ItemCategoryItemStateChanged(evt);
}
});
private void Cmb_ItemCategoryItemStateChanged(java.awt.event.ItemEvent evt) {
if(evt.getStateChange() == java.awt.event.ItemEvent.SELECTED){
System.err.println("Sombody click or change my model content");
}
}
Behind the code, I grab some data, and then calling a method of removeAllItems() .
And then I set a new Model (from new data) into it.
-- at another line of code ---
Cmb_ItemCategory.removeAllItems();
Cmb_ItemCategory.setModel(newModel);
I juz realized that my itemStateChanged() is called when i do the removeAllItem() method. called once.
So, How to make it only called once user Click (select) only AND not when removeAllItems() called?
it similar to this article. But it's not removingItems case. CMIIW.
Here check this code out, this works flawlessly, might be you doing something wrong where you calling removeAllItems() :
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class ComboState
{
private void createAndDisplayGUI()
{
JFrame frame = new JFrame("Combo State Testing : ");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
final JComboBox cbox = new JComboBox();
cbox.addItem("One");
cbox.addItem("Two");
cbox.addItem("Three");
cbox.addItem("Four");
cbox.addItemListener(new ItemListener()
{
public void itemStateChanged(ItemEvent ie)
{
if (ie.getStateChange() == ItemEvent.SELECTED)
{
System.out.println("Item Selected is : " + ie.getItem());
}
/*else
{
System.out.println("I am called for other reasons.");
}*/
}
});
/*
* Click me to remove JComboBox's items.
*/
JButton removeButton = new JButton("REMOVE");
removeButton.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent ae)
{
cbox.removeAllItems();
}
});
frame.add(cbox, BorderLayout.CENTER);
frame.add(removeButton, BorderLayout.PAGE_END);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String... args)
{
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
new ComboState().createAndDisplayGUI();
}
});
}
}
As nIcE cOw already illustrated in his example, it should certainly work when you use a DefaultComboBoxModel (which is the case in his sample code, although it happens behind the screens).
I could explain the behavior you encounter for the non-DefaultComboBoxModel case, although your code snippet suggests you use one. Looking at the source code for JComboBox#removeAllItems there is a different code path since the removeAllElements method is not part of the MutableComboBoxModel interface
public void removeAllItems() {
checkMutableComboBoxModel();
MutableComboBoxModel<E> model = (MutableComboBoxModel<E>)dataModel;
int size = model.getSize();
if ( model instanceof DefaultComboBoxModel ) {
((DefaultComboBoxModel)model).removeAllElements();
}
else {
for ( int i = 0; i < size; ++i ) {
E element = model.getElementAt( 0 );
model.removeElement( element );
}
}
selectedItemReminder = null;
if (isEditable()) {
editor.setItem(null);
}
}
So with a non-DefaultComboBoxModel you are going to remove the items one by one. This means that at a certain point in time, you will remove the selected element. A possible implementation of your model might change the selected element at that point. If you look for example at the implementation in DefaultComboBoxModel (although this code will not be triggered) you can clearly see it changes the selection.
public void removeElementAt(int index) {
if ( getElementAt( index ) == selectedObject ) {
if ( index == 0 ) {
setSelectedItem( getSize() == 1 ? null : getElementAt( index + 1 ) );
}
else {
setSelectedItem( getElementAt( index - 1 ) );
}
}
objects.removeElementAt(index);
fireIntervalRemoved(this, index, index);
}
Perhaps your model does something similar, which explains the event. Just for making this post complete, the code behind the DefaultComboBoxModel#removeAllElements where you can clearly see it sets the selection to null and does not select another object. Only weird thing in that code is that it does not fire a DESELECTED event first, although you know the selection has changed if you listen for the intervalRemoved event ... but that is not really relevant to your problem
public void removeAllElements() {
if ( objects.size() > 0 ) {
int firstIndex = 0;
int lastIndex = objects.size() - 1;
objects.removeAllElements();
selectedObject = null;
fireIntervalRemoved(this, firstIndex, lastIndex);
} else {
selectedObject = null;
}
}
So to conclude: I say the solution for your problem is located in your model, and not in the code you posted
One quick way to do is to have a bool set to true before you call removeAllItem() and back false after. Execute the code in your itemStateChanged() only if the bool variable is false.
Ideally you could override the removeAllItem() function.
not clear from whole discusion,
you have to remove all Listener(s) from JComboBox before removing all Items, after Items are removed you can add Listener(s) back,
still not sure if you want to add & remove Items dynamically, or you can set whatever value for another JComponent(s),
(against complicating simple things) did you see there remove,
.
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
public class ComboBoxTwo extends JFrame implements ActionListener, ItemListener {
private static final long serialVersionUID = 1L;
private JComboBox mainComboBox;
private JComboBox subComboBox;
private Hashtable<Object, Object> subItems = new Hashtable<Object, Object>();
public ComboBoxTwo() {
String[] items = {"Select Item", "Color", "Shape", "Fruit"};
mainComboBox = new JComboBox(items);
mainComboBox.addActionListener(this);
mainComboBox.addItemListener(this);
//prevent action events from being fired when the up/down arrow keys are used
//mainComboBox.putClientProperty("JComboBox.isTableCellEditor", Boolean.TRUE);
getContentPane().add(mainComboBox, BorderLayout.WEST);
subComboBox = new JComboBox();// Create sub combo box with multiple models
subComboBox.setPrototypeDisplayValue("XXXXXXXXXX"); // JDK1.4
subComboBox.addItemListener(this);
getContentPane().add(subComboBox, BorderLayout.EAST);
String[] subItems1 = {"Select Color", "Red", "Blue", "Green"};
subItems.put(items[1], subItems1);
String[] subItems2 = {"Select Shape", "Circle", "Square", "Triangle"};
subItems.put(items[2], subItems2);
String[] subItems3 = {"Select Fruit", "Apple", "Orange", "Banana"};
subItems.put(items[3], subItems3);
// mainComboBox.setSelectedIndex(1);
}
#Override
public void actionPerformed(ActionEvent e) {
String item = (String) mainComboBox.getSelectedItem();
Object o = subItems.get(item);
if (o == null) {
subComboBox.setModel(new DefaultComboBoxModel());
} else {
subComboBox.setModel(new DefaultComboBoxModel((String[]) o));
}
}
#Override
public void itemStateChanged(ItemEvent e) {
if (e.getStateChange() == ItemEvent.SELECTED) {
if (e.getSource() == mainComboBox) {
if (mainComboBox.getSelectedIndex() != 0) {
FirstDialog firstDialog = new FirstDialog(ComboBoxTwo.this,
mainComboBox.getSelectedItem().toString(), "Please wait, Searching for ..... ");
}
}
}
}
private class FirstDialog extends JDialog {
private static final long serialVersionUID = 1L;
FirstDialog(final Frame parent, String winTitle, String msgString) {
super(parent, winTitle);
setModalityType(Dialog.ModalityType.APPLICATION_MODAL);
JLabel myLabel = new JLabel(msgString);
JButton bNext = new JButton("Stop Processes");
add(myLabel, BorderLayout.CENTER);
add(bNext, BorderLayout.SOUTH);
bNext.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent evt) {
setVisible(false);
}
});
javax.swing.Timer t = new javax.swing.Timer(1000, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
setVisible(false);
}
});
t.setRepeats(false);
t.start();
setLocationRelativeTo(parent);
setSize(new Dimension(400, 100));
setVisible(true);
}
}
public static void main(String[] args) {
JFrame frame = new ComboBoxTwo();
frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
}
The method removeAllItems does not call ItemStateChanged, but it call actionPerformed, you can check it by running this simple code:
public class Tuto {
public static void main(String[] args) {
//create the main frame
JFrame frame = new JFrame();
frame.setResizable(false);
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
frame.setLayout(null);
frame.setLocation(new Point(10, 10));
frame.setPreferredSize(new Dimension(400, 300));
JComboBox<String> combo = new JComboBox();
combo.addItem("item 1");
combo.addItem("item 2");
combo.addItem("item 3");
combo.setBounds(50, 30, 300, 20);
combo.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent ae) {
System.out.println(" action Performed ");
}
});
frame.add(combo);
JButton button = new JButton("Remove");
button.setBounds(50, 100, 100, 30);
button.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent ae) {
combo.removeAllItems();
}
});
frame.add(button);
frame.pack();
frame.setVisible(true);
}
}
I want to make an event which will be triggered after i make the selection to the JComboBox.
the problem I'm now facing is that when i added an ActionListener, it was triggered when the user clicked on the box but BEFORE he actually chose the new item, thus the action listener was activated all the time on the previous value which was selected in the box. what i want to do is simply changing the title of an JTextArea according to the selection.
I tried doing something like this:
jBox.addActionListener(new ActionListener(){
#Override
public void actionPerformed(ActionEvent e) {
String alt = GetAlgoAreaTitleByChoice();
panel.remove(jArea);
currentBest = setArea("",alt);
currentBest.setBounds(50, 350, 1000, 290);
panel.add(jArea);
}
});
and the method inside:
private String GetArgsAreaTitleByChoice(){
String chi = jBox.getSelectedItem().toString();
if(chi.equals(generalChoice)){
return "Hello";
}
else if(chi.equals(algoChoice)){
return "World";
}
else if(chi.equals(argsChoice)){
return "Hello";
}
return null;
}
I've tried using the SELECTED events now like this:
public void itemStateChanged(ItemEvent e) {
JComboBox cb = (JComboBox)e.getSource();
// Get the affected item
String item = cb.getSelectedItem().toString();
if (e.getStateChange() == ItemEvent.SELECTED) {
panel.remove(jBox);
textArea = setArea("", item);
panel.add(jBox);
}
but it seems to remove the area from the panel without adding it back... why is this happening?
Here is a simple demonstration with a sample code :
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class Tester {
public Tester(){
JComboBox box = new JComboBox();
box.addItem("One");
box.addItem("Two");
box.addItem("Three");
box.addItemListener(new ItemListener(){
public void itemStateChanged(ItemEvent e){
if(e.getStateChange()==ItemEvent.SELECTED){
e.getItem(); //Do what ever you want :))
}
}
});
JFrame frame = new JFrame();
frame.getContentPane().add(box);
frame.pack();
frame.setVisible(true);
}
public static void main(String [] args) {
Tester tester = new Tester();
}
}
For listening of events from JComboBox is better implements ItemListener, returns two events SELECTED/DESELECTED
EDIT
if you remove/add JComponent(s) on Runtime and in already visible container, then you have to call (as least code lines)
revalidate();
repaint();