java swing about dynamic panel

Question

The structure likes this:

I have a Frame and two button - btnA, btnB

when I press btnA, a createPanel() function will return a panelA to be displayed in the frame,

and so does btnB.

btnA and btnB can be switched.

Before I add the panel into the frame, I use a clearPanel() function to clear the existing panels in the frame.

but the question is when I resize or click the panel, I can see the previous panels that should be removed already.

Is there anything I lost?

public void actionPerformed(ActionEvent e) {
    String buttonString = e.getActionCommand();
    if (buttonString.equals("A")) {
        clearPanel();

        A = new APanel();
        this.getContentPane().add(A.createPanel(), BorderLayout.CENTER);
        this.pack();

        componentMap.put("A", A);
        btnB.setEnabled(true);
        btnA.setEnabled(false);
    }
    else if (buttonString.equals("B")) {
        clearPanel();

        chart = new BPanel();
        this.getContentPane().add(B.createPanel(), BorderLayout.CENTER);
        this.pack();

        componentMap.put("B", B);
        btnA.setEnabled(true);
        btnB.setEnabled(false);
    }
}

private void clearPanel() {
    if (!componentMap.isEmpty()) {  // I store panels in a HashMap
        for (Object o: componentMap.values()) {
            this.getContentPane().remove((JPanel)o);
        }
        this.getContentPane().invalidate();
        componentMap.clear();
    }
}

Answer 1

You are adding A.createPanel() and B.createPanel() to the contentPane but you store A and B in your componentMap. Therefore, when you call this.getContentPane().remove((JPanel)o);, you are doing this on A and/or B which are not in the content pane and therefore you don't remove anything.

You could use a simpler/safer approach if you want to clear the content pane:

this.getContentPane().removeAll();