Returning value from JDialog; dispose(), setVisibl

问题:

I know, that this question appears quite frequently in SO like here: but I would like to present some very specific example... I'm simply not sure if I make things right.

I've got a JDialog in which I can type some values, select some checkboxes... whatever... I've got also some Response object created in MyDialog which represents the MyDialog's "answer".

In JFrame which calls/creates JDialog:

MyDialog d = new MyDialog(this, ...);
d.showDialog();
// After MyDialog is closed (it's modal):
MyDialog.Response dialogResponse = d.getDialogResponse();
// Do something with response...

In Dialog (dialog can be closed by clicking "Save" button):

btnSave.addActionListener(new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent e) {
        dialogResponse = prepareResponse(); // prepares response on the basis of some data introduced by a user; dialogResponse is called from JFrame after Dialog is closed
        setVisible(false);
        dispose();  // <-- Important
    }
});

My question is: This solution works, I mean, the line MyDialog.Response dialogResponse = d.getDialogResponse(); returns proper values, but... if I close the dialog using dispose(), all dialog's resources can be garbage collected (don't have to... hard to predict, am I right?). So is it correct to retrieve my dialog's response it that way... Maybe in this case I should write only setVisible(false); without dispose().

回答1:

Quoted from the Javadocs:

The Window and its subcomponents can be made displayable again by rebuilding the native resources with a subsequent call to pack or show. The states of the recreated Window and its subcomponents will be identical to the states of these objects at the point where the Window was disposed (not accounting for additional modifications between those actions).

So, your Response will be kept. All dispose() does is releasing the native screen resources, other members aren't marked for garbage collection.

Also, if you want to be extra sure, you could just call dispose() right after you retrieved your response object.

回答2:

if I close the dialog using dispose(), all dialog's resources can be garbage collected (don't have to... hard to predict, am I right?). So is it correct to retrieve my dialog's response it that way... Maybe in this case I should write only setVisible(false); without dispose().

• not true that something is GC'ed only non_important value for Graphics/2D

• there isn't some reason to create this Object on runtime, re_use this Object

回答3:

why you don't use class variables (private static or public static) and use a factory method

  //it can be an object too public static Object  getResponseValue()
  public static Integer  getResponseValue(){
    myclassContainer container = new myclassContainer(someparent,modal).setvisible(true)
     return      Myfieldvalue
    }

    private static int Myfielvalue;

}

回答4:

        dialog.add(BorderLayout.CENTER, tree_tmp);
        JButton confirm = new JButton("YES");
        confirm.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                confirm.setActionCommand("kkk");
                dialog.setVisible(false);
            }
        });
        dialog.add(BorderLayout.SOUTH,confirm);
        dialog.setSize(400, 400);
        dialog.setVisible(true);

        System.out.println(confirm.getActionCommand());