the getSource and getActionCommand

Question

What is getSource  and what does it return   and what is getActionCommand   and what does it return    I am getting confused between these two can anyone give or differentiate them to me  what s the use of getSource and getActionCommand   in UI s  specifically TextField or JTextField

User · Answer

I use getActionCommand   to hear buttons  I apply the setActionCommand   to each button so that I can hear whenever an event is execute with event getActionCommand  The setActionCommand   value of the button     I use getSource   for JRadioButtons for example  I write methods that returns each JRadioButton so in my Listener Class I can specify an action each time a new JRadioButton is pressed  So for example   public class SeleccionListener implements ActionListener  FocusListener      So with this I can hear button events and radioButtons events  The following are examples of how I listen each one   public void actionPerformed ActionEvent event        if  event getActionCommand   equals GUISeleccion BOTON ACEPTAR             System out println  Aceptar pressed            In this case GUISeleccion BOTON ACEPTAR is a  public static final String  which is used in JButtonAceptar setActionCommand BOTON ACEPTAR    public void focusGained FocusEvent focusEvent        if  focusEvent getSource   equals guiSeleccion getJrbDat              System out println  Data radio button            In this one  I get the source of any JRadioButton that is focused when the user hits it  guiSeleccion getJrbDat   returns the reference to the JRadioButton that is in the class GUISeleccion  this is a Frame

User · Answer

Assuming you are talking about the ActionEvent class  then there is a big difference between the two methods   getActionCommand   gives you a String representing the action command  The value is component specific  for a JButton you have the option to set the value with setActionCommand String command  but for a JTextField if you don t set this  it will automatically give you the value of the text field  According to the javadoc this is for compatability with java awt TextField   getSource   is specified by the EventObject class that ActionEvent is a child of  via java awt AWTEvent   This gives you a reference to the object that the event came from   Edit     Here is a example  There are two fields  one has an action command explicitly set  the other doesn t  Type some text into each then press enter   public class Events implements ActionListener      private static JFrame frame      public static void main String   args         frame   new JFrame  JTextField events        frame getContentPane   setLayout new FlowLayout          JTextField field1   new JTextField 10       field1 addActionListener new Events         frame getContentPane   add new JLabel  Field with no action command set         frame getContentPane   add field1        JTextField field2   new JTextField 10       field2 addActionListener new Events         field2 setActionCommand  my action command        frame getContentPane   add new JLabel  Field with an action command set         frame getContentPane   add field2         frame setDefaultCloseOperation JFrame EXIT ON CLOSE       frame setSize 220  150       frame setResizable false       frame setVisible true           Override   public void actionPerformed ActionEvent evt        String cmd   evt getActionCommand        JOptionPane showMessageDialog frame   Command      cmd

User · Answer

getActionCommand       Returns the command string associated with this action  This string allows a  modal  component to specify one of several commands  depending on its state  For example  a single button might toggle between  show details  and  hide details   The source object and the event would be the same in each case  but the command string would identify the intended action     IMO  this is useful in case you a single command-component to fire different commands based on it s state  and using this method your handler can execute the right lines of code   JTextField has JTextField setActionCommand java lang String  method that you can use to set the command string used for action events generated by it   getSource       Returns  The object on which the Event initially occurred     We can use getSource   to identify the component and execute corresponding lines of code within an action-listener  So  we don t need to write a separate action-listener for each command-component  And since you have the reference to the component itself  you can if you need to make any changes to the component as a result of the event   If the event was generated by the JTextField then the ActionEvent getSource   will give you the reference to the JTextField instance itself

User · Answer

The getActionCommand   method returns an String associated with that Component set through the setActionCommand     whereas the getSource   method returns an Object of the Object class specifying the source  of the event

[java] the getSource() and getActionCommand()

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