Listeners in SWT

[K Terr]

Hi,

i was wondering if someone can help me. i'm new to swt, and i am trying to work with two listeners. I have a login screen that a user enters their username and password and then clicks login button. when they click login their is a SelectionListener that will envoke a login method. i also have a listener on the shell that if the user clicks the close (X) button then the entire application just exits. the problem i'm having is that when the user clicks login it is actually exiting the application when it shouldn't. i have added some code at the end. Any help would be greatly appreciated.

Thanks in advanced

k

public class Login
{
Display display = new Display ();
final Shell shell = new Shell (display);

final Label label1, label2;
final Button button1;
final Text textField1, textField2;
   
public Login()
{
// Label and Textfield info
     
    button1 = new Button(shell, SWT.BUTTON1);
    button1.setSize(90,30); // (width, height)
    button1.setLocation(220,75); // (x,y) co-ordinates
    button1.setText("Login"); 
    button1.addSelectionListener(login);
    
    shell.setSize(340, 340); // (width, height)    
    shell.setImage(img1);
    shell.setText("Login");
    shell.open ();

    shell.addListener(SWT.Close, new Listener() 
    {
    public void handleEvent(Event event) 
    {
    int style = SWT.APPLICATION_MODAL | SWT.OK;
    MessageBox msgBox = new MessageBox(shell, style);
    msgBox.setText("Closing");
    msgBox.setMessage("Application is now Closing");
    //event.doit = messageBox.open() == SWT.YES;
    
    int response = msgBox.open();
        
    if (response == SWT.OK)
    {
    System.exit(0);
}
    } // end handle event    
    }); // end addListener

while (!shell.isDisposed ())
{
  if (!display.readAndDispatch ()) display.sleep();
}
display.dispose ();
new mainApp();

} // end constructor

SelectionListener login = new SelectionListener()
{
public void widgetSelected(SelectionEvent arg0)
{
String response1 = textField1.getText();
String response2 = textField2.getText();
 
 if (!response1.equals("") && !response2.equals(""))
{
  new Database(response1, response2);
    shell.close();
} // end if

 else
 {
         MessageBox messageBox = new MessageBox(shell, SWT.ICON_WARNING);
        messageBox.setText("Error");
        messageBox.setMessage("You Must Enter Both ID & Password");
        
        int buttonID = messageBox.open();
 } // end else
}// end widgetSelected() method
 
public void widgetDefaultSelected(SelectionEvent arg0) {}
}; // end SelectionListener method

} // end class
 

[Campbell Ritchie]

Most of these classes are unfamiliar to me, but I think you have added a Listener to your Shell with the possibility of calling System.exit(0). That will of course close your entire app.
Was that what you intended?

[K Terr]

Hi,

Thanks for replying. yeah if they hit the X button in the top right hand corner then i want the application to close. if the hit the login button i want the next screen to appear. i think its because i put a listener on the shell but i dont know a way around this.

thanks again

k

[Campbell Ritchie]

The more usual way to close the app on clicking the "X" at the top right is to set the properties of the enclosing JFrame. I presume you are familiar with the three things you have to do when setting up a JFrame?

public class DisplayFrame extends JFrame
. . .
public void setUpGui()
{
   DisplayFrame frame = new DisplayFrame("Title to Display");
   frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
   frame.setBounds(50, 50, 200, 200);
   frame.setVisible(true);
}// end set up GUI method

There are several alternatives for setBounds, eg setSize (I don't know about setPreferredSize).

The default close operation for a JFrame is "HIDE_ON_CLOSE," so you usually change it to EXIT_ON_CLOSE. That of course obviates any need for a closing listener, unless you have a button or menu item marked "Close," or "Exit."

And try adding all your Listeners to the buttons; if you add the Listeners to other components you end up with a somethingOrOtherPerformed(SomeEventOrOther e){} method with a long list of if and else if blocks in.

I have my own ideas, and fulminate regularly about ActionListeners on these boards, for example here. Add a Listener to each of your buttons; if the Listener has lots to do, just put a method call in its actionPerformed() method which deals with its action.