Can`t contact to the child Component in JInternalFrame!!!

Question

I have made JInternalFrames, which have the child component( a TextArea).
with JFrame set the ContentPane with JDesktopPane, now I am trying to contact to the TextArea.
<<<<<below is sample code for original>>>>
JInternalFrame internalFrame = desktopPane.getSelectedFrame();
internalFrame.getTextArea().append("Test String\n");
------------------ Error here --------------------------------------
InternalFrameDemo.java:191: cannot resolve symbol
symbol : method getTextAreat()
location: class javax.swing.JInternalFrame
               innerFrame.getTextArea().append(txtField+"\n");
.................................^
1 error
the "getTextArea()" method in [public class MyinternalFrame] is
.....public JTextArea getTextArea(){
.........return txtarea;
.....} // public JTextArea txtarea = new JTextArea(10, 36);
method getTextArea() is correct, and is internalFrame so.
but i dont know the reason internalFrame cannot find its own method, getTextArea().
please give me answer....
if you want, the source is located at
http://home.dongguk.edu/user/yong/javaBug/InternalFrameDeom.zip

Answer 1

In your actionPerformed()-Method, use
JInternalFrame innerFrame = InternalFrameDemo.desktop.getSelectedFrame();
if (innerFrame instanceof MyInternalFrame) {
  ((MyInternalFrame)innerFrame).getTextArea().append(txtField+"\n");
}Hope that helps,
bye