用按钮显示/隐藏 JLabel？

Question

Currently the code only hides the JLabel. I'm not sure why it's not making it visible when I click the button again. Hopefully this is an easy fix

        contentPane.add(btnSwap);   
    btnHide.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent arg0) {
            lblHello.setVisible(false);
        }
    }); 
    contentPane.add(btnHide);
    btnHide.setBounds(185, 199, 89, 23);
    lblHello.setVisible(true);

}

Answer 1

I'm not sure why it's not making it visible when I click the button again.

Why should it, since all the ActionListener does (the code that's called on button press) is to continually set the label invisible?

A solution is to simply toggle its visibility:

lblHello.setVisible(!lblHello.isVisible());

Note that to be safe, it's best to revalidate and repaint the container after making such changes, so:

btnHide.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent arg0) {
        lblHello.setVisible(!lblHello.isVisible());
        revalidate();
        repaint();
    }
}); 

as this will rid the GUI of "dirty" pixels that can occur from adding and especially from removing visible components.

---

A word on this:

btnHide.setBounds(185, 199, 89, 23);

This suggests that you're using null layouts with setBounds(...) . While this often seems to newbie Swing coders the best way to create complex GUI's, it will come back to haunt them later, since this will mean that the GUI will look OK on one platform and one platform only, and that if later you want to enhance or improve the GUI, it can only be done with much difficulty and risk of bugs. Much better is to learn and use the layout managers.

---

Another recommendation:

If your desire is to change the appearance of the GUI on button press, then also have a look at the CardLayout (please check the CardLayout Tutorial ) as this can be a way to cleanly and easily swap views

---

And a better recommendation:

Since a JLabel only shows its text or its icon or both, the best way to make it "invisible" is to remove its text and its icon, as noted by Andrew Thompson below:

// get rid of its text
lblHello.setText("");

// and if needed
lblHello.setIcon(null);

This won't work for text components such as JTextFields and JTextAreas or other components that have more "heft" than a JLabel including pretty much all other user-interaction components.

Answer 2

Try :

btnChangeLabelVisibilityButton.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent arg0) {
        lblHello.setVisible(!lblHello.isVisible());
    }
});