Populating JTextField based on latest KeyStroke

Question

The use case in my UI is to populate two JTextField components based on double clicking items in a JList. The easy was is to use a JCheckBox populate jTextField1 if the checkbox is selected, and populate the other if it is not selected or vice versa which is working perfectly.

But I would like to explore if this can be done without the checkbox.

As in, if I type something in jtextfield1 and double click the item in list to complete the text, the item clicked should be appended to jtextfield1 based on fetching the latest KeyStroke I used.

Is there are any way to do this?

Answer 1

The use case in my UI is to populate two jTextField's based on double clicking items in a jlist.

Well, normally a UI should be designed so that you can use the mouse or the keyboard to invoke an Action. That is you should be able to double click or use the Enter key on the selected item.

Check out List Action for a simple class that allows you to implement this functionality by using an Action.

Now when you create your Action you can extend TextAction. Then you can use the getFocustComponent() method from the TextAction to determine the text component that last had focus and add the text from the selected item to that text field.

The basic code for the custom Action would be:

JList list = (JList)e.getSource();
JTextComponent textField = getFocusedComponent();
textField.setText( list.getSelectedValue().toString() );

Note: you will need to verify if focus is on one of the two fields if your window contains more than two text components.

To use the FocusListener approach you would need to define an instance variable in your class:

private JTextField lastFocusedTextField = null;

Then in the constructor of your class where you create the text fields you would create the listener:

FocusListener fl = new FocusAdapter()
{
    @Override
    public void focusGained(FocusEvent e)
    {
        lastFocusedTextField = (JTextField)e.getSource();
    }
};

JTextField textField1 = new JTextField(...);
textField1.addFocusListener( fl );
// same for the other text field

Now you need to add a MouseListener to the JList. In the mouseClicked(...) method you do something like:

JList list = (JList)e.getSource();
lastFocusedTextField.setText( list.getSelectedValue().toString() );

So you need:

1. an instance variable
2. a FocusListener
3. a MouseListener

Answer 2

As everyone has suggested initialize a FocusListener to both the text fields and and point it to a string variable when either of the loses focus.

Code:

String LastFocusLost = null;

jTextField1.addFocusListener(new java.awt.event.FocusAdapter()
 {
  public void focusLost(java.awt.event.FocusEvent evt)
     {
      LastFocusLost = "jTextField1";
     }  
 });

jTextField2.addFocusListener(new java.awt.event.FocusAdapter()
 {
  public void focusLost(java.awt.event.FocusEvent evt)
     {
      LastFocusLost = "jTextField2";
     }  
 });

In the mouseListener add a if-else then:

if ("jTextField1".equals(LastFocusLost))
 {
   //;
 }

else if ("jTextField2".equals(LastFocusLost))
 {
  //;
 }