Processing a Return or Enter Key

[Kaydell Leavitt]

I need to detect when a carriage return in pressed and take an action. I need to do this both for a JTable and for a JTextComponent.

For the JComponent, it's for a store receiving merchandise with a barcode. The barcode is terminated by a carriage return.
Here is what I have for this:


class ReceivingText extends LengthText implements Keymap {
...
}

LengthText is one of my classes. It's just a JTextComponent that limits how long the text can be.

I'm confused by all of the methods that I have to implement from the Keymap interface.

I also need to process carriage returns in a JTable. Here is what I have so far:

private class TableEditor extends LengthText implements TableCellEditor, Keymap {
..
}

Again, I'm confused by all of the methods of TableCellEditor and Keymap.

Am I on the right track, implementing the Keymap and the TableCellEditor interfaces and if so, how do I proceed?

Thanks for reading my questions.

[Kaydell Leavitt]

OK. I went ahead by myself and I was able to code-up a solution for when the user presses return or enter (or when a barcode is scanned and I get a carriage return character at the end of the input).

	private void receive() {
		KAlert.showMessageDialog(this, "receive() was called");		
	}
	
	private class ReceiveAction implements Action {

		@Override
		public void actionPerformed(ActionEvent arg0) {
			receive();
		}

		@Override
		public void addPropertyChangeListener(PropertyChangeListener arg0) {
		}

		@Override
		public Object getValue(String arg0) {
			// TODO Auto-generated method stub
			return null;
		}

		@Override
		public boolean isEnabled() {
			return true;
		}

		@Override
		public void putValue(String arg0, Object arg1) {
		}

		@Override
		public void removePropertyChangeListener(PropertyChangeListener arg0) {
		}

		@Override
		public void setEnabled(boolean arg0) {
		}
		
	}

	@SuppressWarnings("serial")
	private class ReceivingText extends LengthText implements Keymap {
		
		private Keymap oldKeymap;
	
		public ReceivingText(int maxLength) {
			super(maxLength);
			oldKeymap = getKeymap();
			setKeymap(this);
		}
	
		@Override
		public void addActionForKeyStroke(KeyStroke key, Action a) {			
		}
		
		private KeyStroke getCarriageReturn() {
			KeyStroke carriageReturn = KeyStroke.getKeyStroke('\n');
			return carriageReturn;
		}
	
		@Override
		public Action getAction(KeyStroke key) {
			if (key.equals(getCarriageReturn()))
				return new ReceiveAction();
			else
				return oldKeymap.getAction(key);
		}
	
		@Override
		public Action[] getBoundActions() {
			return null;
		}
	
		@Override
		public KeyStroke[] getBoundKeyStrokes() {
			return null;
		}
	
		@Override
		public Action getDefaultAction() {
			return oldKeymap.getDefaultAction();
		}
	
		@Override
		public KeyStroke[] getKeyStrokesForAction(Action a) {
			return null;
		}
	
		@Override
		public Keymap getResolveParent() {
			return null;
		}
	
		@Override
		public boolean isLocallyDefined(KeyStroke key) {
			return false;
		}
	
		@Override
		public void removeBindings() {
		}
	
		@Override
		public void removeKeyStrokeBinding(KeyStroke keys) {
		}
	
		@Override
		public void setDefaultAction(Action a) {
		}
	
		@Override
		public void setResolveParent(Keymap parent) {
		}
	
	}
	

This seems to work, but is an awful lot of code. Am I going about this right?

[Rob Spoor]

First of all, you should rarely need to implement Action. Extending AbstractAction is a much more common approach.

For the text component, there are two ways I can think of:
- use a KeyListener or key binding (using InputMap and ActionMap) if the contents are only entered from the user interface.
- use a DocumentListener if the contents can come from code as well.

[Kaydell Leavitt]

OK. Thank you. I got a KeyListener to work for me.

I'm still puzzled by how to install my own editor in a JTable. Ideally, I want to install my own subclass of JTextField that already knows how to look for carriage returns and calls the appropriate method.

[Darryl Burke]

A DocumentListener is the way to go. Even f the contents are only entered from the user interface, you can't rule out Ctrl-V to paste text that includes a newline.

[Rob Spoor]

Kaydell Leavitt wrote:I'm still puzzled by how to install my own editor in a JTable. Ideally, I want to install my own subclass of JTextField that already knows how to look for carriage returns and calls the appropriate method.

I think the easiest way is to use a DefaultCellEditor that you construct with a JTextField with the appropriate support added to it. I'm not 100% sure the listeners will work like this, you'll need to check that out.

[Kaydell Leavitt]

Thanks again for this other tip about DefaultCellEditor, but I can't get it to work. Here is my code:

		jTextField = new JTextField();
		setCellEditor(new DefaultCellEditor(jTextField));

The JTable doesn't seem to be using my jTextField. What am I doing wrong?

-- Kaydell

[Kaydell Leavitt]

I figured out how to get my cell editor to work. For some reason, I have to set it for every column. When I try to set a table cell editor for the whole JTable, it doesn't seem to do anything.

		tableText = new TableText(LengthText.UNLIMITED);
		for (int i = 0; i < getColumnCount(); i++) {
			TableColumn col = getColumnModel().getColumn(i);
			col.setCellEditor(new DefaultCellEditor(tableText));
		}

[Rob Spoor]

Or just set it as the default cell editor for Object.class. Unless the table or model returns different classes in getColumnClass this should then be used for all columns.

Also, if you still want to do it your way, you can make all columns share the same cell editor instance. Declare and initialize it outside the loop, then set it inside.