Try this one
import com.google.gwt.event.dom.client.KeyCodes;
import com.google.gwt.i18n.client.DateTimeFormat;
import com.google.gwt.user.client.Event;
import com.google.gwt.user.client.Event.NativePreviewEvent;
...
Event.addNativePreviewHandler(new Event.NativePreviewHandler() {
@Override
public void onPreviewNativeEvent(final NativePreviewEvent event) {
if (event.getTypeInt() == Event.ONKEYPRESS) {
if (event.getNativeEvent().getKeyCode() == KeyCodes.KEY_BACKSPACE) {
System.out.println("Back space is pressed");
}
}
}
});
t1.sinkEvents(Event.ONKEYPRESS);