JCheckbox - ActionListener and ItemListener

Question

Both ActionListener and ItemListener are used to fire an event with JCheckBox    So  what s the difference between them and in which case one of them is preferred to the other

User · Answer

The difference is that ActionEvent is fired when the action is performed on the JCheckBox that is its state is changed either by clicking on it with the mouse or with a space bar or a mnemonic  It does not really listen to change events whether the JCheckBox is selected or deselected   For instance  if JCheckBox c1  say  is added to a ButtonGroup  Changing the state of other JCheckBoxes in the ButtonGroup will not fire an ActionEvent on other JCheckBox  instead an ItemEvent is fired   Final words  An ItemEvent is fired even when the user deselects a check box by selecting another JCheckBox  when in a ButtonGroup   however ActionEvent is not generated like that instead ActionEvent only listens whether an action is performed on the JCheckBox  to which the ActionListener is registered only  or not  It does not know about ButtonGroup and all other selection deselection stuff

User · Answer

I use addActionListener for JButtons while addItemListener is more convenient for a JToggleButton  Together with if event getStateChange    ItemEvent SELECTED   in the latter case  I add Events for whenever the JToggleButton is checked unchecked

User · Answer

I ve been testing this myself  and looking at all the answers on this post and I don t think they answer this question very well  I experimented myself in order to get a good answer  code below   You CAN fire either event with both ActionListener and ItemListener 100  of the time when a state is changed in either a radio button or a check box  or any other kind of Swing item I m assuming since it is type Object  The ONLY difference I can tell between these two listeners is the type of Event Object that gets returned with the listener is different  AND you get a better event type with a checkbox using an ItemListener as opposed to an ActionListener   The return types of an ActionEvent and an  ItemEvent will have different methods stored that may be used when an Event Type gets fired  In the code below the comments show the difference in  get methods for each Class returned Event type   The code below sets up a simple JPanel with JRadioButtons  JCheckBoxes  and a JLabel display that changes based on button configs  I set all the RadioButtons and  CheckBoxes up with both an Action Listener and an Item Listener   Then I wrote the Listener classes below with ActionListener fully commented because I tested it first in this experiment  You will notice that if you add this panel to a frame and display  all radiobuttons and checkboxes always fire regardless of the Listener type  just comment out the  methods in one and try the other and vice versa       Return Type into the implemented methods is the MAIN difference between the two  Both Listeners fire events the same way  Explained a little better in comment above is the reason a checkbox should use an ItemListener over ActionListener due to the Event type that is returned    package EventHandledClasses  import javax swing    import java awt    import java awt event     public class RadioButtonsAndCheckBoxesTest extends JPanel  JLabel display  String funny  serious  political  JCheckBox bold italic  JRadioButton funnyQuote  seriousQuote  politicalQuote  ButtonGroup quotes       public RadioButtonsAndCheckBoxesTest            funny    You are not ugly  you were just born    different           serious    Recommend powdered soap in prison            political    Trump can eat a little Bernie  but will choke on his     Birdie            display   new JLabel funny           Font defaultFont   new Font  Ariel  Font PLAIN 20           display setFont defaultFont            bold   new JCheckBox  Bold  false           bold setOpaque false           italic   new JCheckBox  Italic  false           italic setOpaque false              Color itemBackground            funnyQuote   new JRadioButton  Funny  true           funnyQuote setOpaque false           seriousQuote   new JRadioButton  Serious            seriousQuote setOpaque false           politicalQuote   new JRadioButton  Political            politicalQuote setOpaque false            quotes   new ButtonGroup            quotes add funnyQuote           quotes add seriousQuote           quotes add politicalQuote            JPanel primary   new JPanel            primary setPreferredSize new Dimension 550  100             Dimension standard   new Dimension 500  30            JPanel radioButtonsPanel   new JPanel            radioButtonsPanel setPreferredSize standard           radioButtonsPanel setBackground Color green           radioButtonsPanel add funnyQuote           radioButtonsPanel add seriousQuote           radioButtonsPanel add politicalQuote            JPanel checkBoxPanel   new JPanel            checkBoxPanel setPreferredSize standard           checkBoxPanel setBackground Color green           checkBoxPanel add bold           checkBoxPanel add italic            primary add display           primary add radioButtonsPanel           primary add checkBoxPanel              Add Action Listener To test Radio Buttons         funnyQuote addActionListener new ActionListen             seriousQuote addActionListener new ActionListen             politicalQuote addActionListener new ActionListen                Add Item Listener to test Radio Buttons         funnyQuote addItemListener new ItemListen             seriousQuote addItemListener new ItemListen             politicalQuote addItemListener new ItemListen                Add Action Listener to test Check Boxes         bold addActionListener new ActionListen             italic addActionListener new ActionListen                Add Item Listener to test Check Boxes         bold addItemListener new ItemListen             italic addItemListener new ItemListen                adds primary JPanel to this JPanel Object         add primary                 private class ActionListen implements ActionListener           public void actionPerformed ActionEvent e                          Different Get Methods from  ItemEvent           e getWhen            e getModifiers            e getActionCommand                    int font Font PLAIN              if bold isSelected                     font    Font BOLD                            if italic isSelected                     font    Font ITALIC                            display setFont new Font  Ariel  font 20                 if funnyQuote isSelected                     display setText funny                             if seriousQuote isSelected                     display setText serious                             if politicalQuote isSelected                     display setText political                                       private class ItemListen implements ItemListener            public void itemStateChanged ItemEvent arg0                                Different Get Methods from ActionEvent             arg0 getItemSelectable               arg0 getStateChange               arg0 getItem                   int font Font PLAIN              if bold isSelected                     font    Font BOLD                            if italic isSelected                     font    Font ITALIC                            display setFont new Font  Ariel  font 20                 if funnyQuote isSelected                     display setText funny                             if seriousQuote isSelected                     display setText serious                             if politicalQuote isSelected                     display setText political

User · Answer

For reference  here s an sscce that illustrates the difference  Console    SELECTED ACTION PERFORMED DESELECTED ACTION PERFORMED   Code   import java awt EventQueue  import java awt event ActionEvent  import java awt event ActionListener  import java awt event ItemEvent  import java awt event ItemListener  import javax swing JCheckBox  import javax swing JFrame  import javax swing JPanel        see http   stackoverflow com q 9882845 230513    public class Listeners        private void display             JFrame f   new JFrame  Listeners            f setDefaultCloseOperation JFrame EXIT ON CLOSE           JCheckBox b   new JCheckBox  JCheckBox            b addActionListener new ActionListener                   Override             public void actionPerformed ActionEvent e                    System out println e getID      ActionEvent ACTION PERFORMED                        ACTION PERFORMED    e getID                                       b addItemListener new ItemListener                   Override             public void itemStateChanged ItemEvent e                    System out println e getStateChange      ItemEvent SELECTED                        SELECTED     DESELECTED                                      JPanel p   new JPanel            p add b           f add p           f pack            f setLocationRelativeTo null           f setVisible true              public static void main String   args            EventQueue invokeLater new Runnable                   Override             public void run                     new Listeners   display

User · Answer

Both ItemListener as well as ActionListener  in case of JCheckBox have the same behaviour  However  major difference is ItemListener can be triggered by calling the setSelected true  on the checkbox  As a coding practice do not register both ItemListener as well as ActionListener with the JCheckBox  in order to avoid inconsistency

[java] JCheckbox - ActionListener and ItemListener?

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