Re: How to get reference for JFrame

From:
Michael Rauscher <michlmann@gmx.de>
Newsgroups:
comp.lang.java.gui
Date:
Thu, 09 Apr 2009 13:05:53 +0200
Message-ID:
<grkkqe$e1i$02$1@news.t-online.com>
Coolm@x wrote:

Hello,
I want to ask for an example. I want to run JDialog from JMenuItem. I
have JFrame in one file and JDialog in another. As far as I know I must
pass frame-parent as argument to JDialog. Examples which I found were
similar to:

JFrame frame = new JFrame();
JDialog dialog = new JDialog(frame (...)

Code is in one class, so there is no problem. I don't know how to pass
argument in this:


....

Is there any method to get jFrame parent? Also, is this code correct:
JDabout about = new JDabout(?);


If you're able to obtain the component where the ActionEvent originated
from, you can obtain the frame where the component lives in, too.

class Util {
     // ...
     public static Frame getFrameAncestor(Component c) {
         Frame frame = null;
         Window w = SwingUtilities.getWindowAncestor(c);
         if ( w instanceof Frame )
             frame = (Frame) w;
         return frame;
     }
}

(Of course, you can rewrite the above method to be more Frame specific
by walking up the component hierarchy)

Fortunately, the ActionEvent provides it's source which often is-a
component. Therefore you can do something like this:

public void actionPerformed(ActionEvent e) {
     Frame frame = null;
     Object source = e.getSource();
     if ( source != null && source instanceof Component ) {
         frame = Util.getFrameAncestor((Component) source);
     }

     // it's perfectly legal to pass the null-reference to JDialog.
     JDabout dlg = new JDabout(frame);
}

HTH
Michael

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