SWT – How to capture keyboard event

By mkyong | Updated: January 7, 2009

Viewed: 653 (+4 pv/w)

Tags: swt

In SWT, keyboard event is represent by KeyEvent class. We can use KeyListener to receive and process a KeyEvent.

The KeyEvent class has three member fields to provide information about the key that generated by event.

1) character – Display a char value of the pressed key.
2) stateMask – Check whether any other keys currently pressed. (common use to capture CTRL, ALT and SHIFT keys).
3) keyCode – Display a digit value of the pressed key.

We can attach a KeyListener() or KeyAdapter() to a widget control to keep track the keyboard event.

"widget control".addKeyListener(new KeyAdapter()
{	
		public void keyPressed(KeyEvent e)
		{
		}
});

Check whether ALT key is currently pressed

if ((e.stateMask & SWT.ALT) != 0) 

Check whether BACKSPACE key is pressed

if(e.keyCode == SWT.BS)

P.S Please Check SWT class for other keyboard events.

Check whether any character is pressed

if(e.keyCode >=97 && e.keyCode <=122)

Check whether any digit is pressed

if(e.keyCode >=48 && e.keyCode <=57)

Here is the full source how to demonstrate how to capture the keyboard event.

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.KeyAdapter;
import org.eclipse.swt.events.KeyEvent;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
 
public class SWTKeyEvent
{
	public static void main (String [] args) {
		Display display = new Display ();
		Shell shell = new Shell(display);
		shell.setText("SWT KeyEvent Example");
	 
		shell.setLayout(new FillLayout());

		Button button = new Button(shell, SWT.CENTER);
		
		button.setText("Type Something");
		
		button.addKeyListener(new KeyAdapter()
		{	
			public void keyPressed(KeyEvent e)
			{
				String string = "";
				
				//check click together?
				if ((e.stateMask & SWT.ALT) != 0) string += "ALT - keyCode = " + e.keyCode;
				if ((e.stateMask & SWT.CTRL) != 0) string += "CTRL - keyCode = " + e.keyCode;
				if ((e.stateMask & SWT.SHIFT) != 0) string += "SHIFT - keyCode = " + e.keyCode;
				
				if(e.keyCode == SWT.BS)
				{
					string += "BACKSPACE - keyCode = " + e.keyCode;
				}
				
				if(e.keyCode == SWT.ESC)
				{
					string += "ESCAPE - keyCode = " + e.keyCode;
				}
				
				//check characters 
				if(e.keyCode >=97 && e.keyCode <=122)
				{
					string += " " + e.character + " - keyCode = " + e.keyCode;
				}

				//check digit
				if(e.keyCode >=48 && e.keyCode <=57)
				{
					string += " " + e.character + " - keyCode = " + e.keyCode;
				}
				
				if(!string.equals(""))
					System.out.println (string);
			}
		});
		
		shell.open();
	 
		while (!shell.isDisposed ()) {
			if (!display.readAndDispatch ()) display.sleep ();
		}
		display.dispose ();
	}

}