Question

I need to access gui components outside the class that defines them.
My gui class contain the following code for placing object on it:

/**
 * Create contents of the window.
 */
protected void createContents() {
    shlCertificatesmanager = new Shell(Display.getDefault());
    shlCertificatesmanager.setSize(450, 300);
    shlCertificatesmanager.setText("CertificatesManager");
    shlCertificatesmanager.setLayout(new RowLayout(SWT.HORIZONTAL));
    MenuItemListener menuListener = new MenuItemListener(shlCertificatesmanager);

    Menu menu = new Menu(shlCertificatesmanager, SWT.BAR);
    shlCertificatesmanager.setMenuBar(menu);

    MenuItem mntmNewSubmenu = new MenuItem(menu, SWT.CASCADE);
    mntmNewSubmenu.setText("File");     

    Menu menu_1 = new Menu(mntmNewSubmenu);
    mntmNewSubmenu.setMenu(menu_1);

    MenuItem mntmOpenCertificate = new MenuItem(menu_1, SWT.NONE);
    mntmOpenCertificate.setText("Open Certificate");
    mntmOpenCertificate.addSelectionListener(menuListener);

    MenuItem mntmExit = new MenuItem(menu_1, SWT.NONE);
    mntmExit.addSelectionListener(menuListener);
    mntmExit.setText("Exit");

    MenuItem mntmHelp = new MenuItem(menu, SWT.CASCADE);        
    mntmHelp.setText("Help");

    Menu menu_2 = new Menu(mntmHelp);
    mntmHelp.setMenu(menu_2);

    MenuItem mntmAbout = new MenuItem(menu_2, SWT.NONE);
    mntmAbout.setText("About");
    mntmAbout.addSelectionListener(menuListener);

    Label lblAliasName = new Label(shlCertificatesmanager, SWT.NONE);
    lblAliasName.setText("Alias name: ");

    Label label = new Label(shlCertificatesmanager, SWT.NONE);
    label.setText("___________");

}

Now my need is to access some of these component from an external class, in that case i need to access the two labels (lblAliasName, label) from MenuItemListener class.

There is a way to access them? (maybe like Android with a findViewById method or similar?)

Or i need for example made them accessible from the other class in some way? (Creating a calss of gui components that will be used by both MenuItemListener class and GuiWindow class)

Answer 1

Two options come to my mind:

1. If there is only one instance of your class, declare the components as static fields and hand them over via getter methods.
2. If there is more than one instance, declare the components as fields (this time not static) and create getter methods. The other class would of course have to know the instance of your class to access the methods then.

Keep in mind:

If you try to change components from a thread that is not the gui-thread, you will get an SWTException with value ERROR_THREAD_INVALID_ACCESS.

You can solve this by using:

Display.getDefault().asyncExec(new Runnable() {
    public void run() {
        // change/modify components here
    }
});