Dynamically change jButton icon

Question

I have a program that detects when certain machines are online and creates a button with a green "online" icon to show this. I want to add the functionality to check periodically if this machine is still online, and if it's not, change the icon to the "offline" icon that I've already defined.

Answer 1

I know how to set the icon, however I can't figure out a way to do it once the button has already been displayed

probably you have issues with Concurency in Swing, that means that all Swing code must be done on EDT

then you have to wrap myButton.setIcon(myIcon) to the invokeLater(), for example

SwingUtilities.invokeLater(new Runnable() {

    @Override
    public void run() {
        myButton.setIcon(myIcon);
    }
});

Answer 2

I have a program that detects when certain machines are online and creates a button with a green "online" icon to show this.

Use a JToggleButton instead, as shown here¹ & here².

I can't figure out a way to do it once the button has already been displayed.

To toggle the state and fire an action event doClick() or alternately setSelected(boolean).

Screenshots

1. 
2. 

Answer 3

You should be able to do so using AbstractButton.setIcon(). It may require you to call invalidate() on the button to get the change displayed.

changeButton = new JButton(icon1);
changeButton.addActionListener(
    new ActionListener( )
    {
        private boolean flag = true;

        @Override
        public void actionPerformed( ActionEvent arg0 )
        {
            changeButton.setIcon( flag ? icon2 : icon1 );
            flag = !flag;
        }
    }
);
add(changeButton);

Answer 4

btn1.setIcon(new javax.swing.ImageIcon(getClass().getResource("/url.png")));

Answer 5

you can add an action listener on the button, then in its called function change the icon - here is an example :

public yourDialogSwing() {

        Yourbutton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                onButtonPressed();
            }
        });
}

private void onButtonPressed() {
       YourButton.setIcon(YourButton.getPressedIcon());
}