How to be notified that a composite's child received/lost focus?

Question

I have an SWT Composite that I need to pass to some other code which will add children to it at will. Is there any way to be notified that a child of the composite

Answer 1

Have you checked this link: SWT: notify a composite that it has a new child

As per the proposed solution in the above link the only possible solution is to use the resize event. Based on that see the following code, which adds a focus listener on all the immediate child nodes. Though the solution itself is not very elegant.

Test Code

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.ControlEvent;
import org.eclipse.swt.events.ControlListener;
import org.eclipse.swt.events.FocusEvent;
import org.eclipse.swt.events.FocusListener;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;

public class SWTApplication 
{
    public static void main(String[] args) {
        new SWTApplication().initSystem("Children Notification");
    }

    private Display display;
    private Shell shell;

    public void initSystem(String windowName)
    {
        display = new Display();
        shell = new Shell(display);
        shell.setText(windowName);
        shell.setLayout(new GridLayout(6, true));
        shell.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));

        final TestFocusListener listener = new TestFocusListener();

        shell.addControlListener(new ControlListener() {
            public void controlResized(ControlEvent e) {
                if(e.getSource() instanceof Shell)
                {
                    Shell s = (Shell)e.getSource();
                    Control[] children = s.getChildren();
                    for (int i = 0; i < children.length; i++) 
                    {
                        Control c = children[i];
                        c.removeFocusListener(listener);
                        c.addFocusListener(listener);
                    }
                }
            }
            public void controlMoved(ControlEvent e) {
            }
        });


        createControls();

        shell.open();
        while (!shell.isDisposed()) {
            if (!display.readAndDispatch())
                display.sleep();
        }

        display.dispose();
    }

    private void createControls() 
    {
        String[] name = {"a", "b", "c", "d", "e", "f"};
        for(int i=0; i<6; i++)
        {
            Button button = new Button(shell, SWT.PUSH);
            button.setText(name[i] + " button");
            button.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, false));
            shell.setSize(shell.computeSize(SWT.DEFAULT, SWT.DEFAULT));
        }
    }

    class TestFocusListener implements FocusListener
    {
        public void focusGained(FocusEvent e) {
            Object src = e.getSource();
            if(src instanceof Button)
            {
                System.out.println("Focus gained: " + ((Button)src).getText());
            }

        }
        public void focusLost(FocusEvent e) {
            Object src = e.getSource();
            if(src instanceof Button)
            {
                System.out.println("Focus lost: " + ((Button)src).getText());
            }
        }
    }

}