按下按钮时图像更改Java

Question

Okay I want my background image to change when helpButton is pressed. I can make the button image change when the mouse hovers over it with a Mouse Listener. I did the same steps except with the Action Listener but with no success. Any help would be great!

public class test extends JFrame{

    private JLabel label;
    private JButton button;

    private ImageIcon bgi;
    private JLabel bgl;

    public static Rectangle gameSquare;


    private JButton startButton;
    private JButton helpButton;
    private final Action action = new SwingAction();


    public static void main(String[] args) throws MalformedURLException, IOException {
        test gui = new test ();
        gui.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); // when click x close program
        gui.setSize(902, 305);
        gui.setVisible(true);
        gui.setTitle("Solid Cloud Inc - Twitter Unfolower");
    }

    public test() throws MalformedURLException, IOException{

        bgi = new ImageIcon(getClass().getResource("tu.png"));
        getContentPane().setLayout(null);

        BufferedImage img = ImageIO.read(new URL("http://i1344.photobucket.com/albums/p656/SolidCloudInc/start_zpsf3781681.png"));
        //ImageIcon start = new ImageIcon(getClass().getResource("start.png"));
        startButton = new JButton("");
        startButton.setIcon(new ImageIcon(img));
        startButton.setBounds(22, 186, 114, 50);


        getContentPane().add(startButton);

        BufferedImage img2 = ImageIO.read(new URL("http://i1344.photobucket.com/albums/p656/SolidCloudInc/help_zpsc4fad867.png"));
        final JButton helpButton = new JButton("");
        helpButton.setIcon(new ImageIcon(img2));
        helpButton.setBounds(192, 186, 114, 50);

        getContentPane().add(helpButton);

        bgl = new JLabel (bgi);
        bgl.setBounds(0, 0, 886, 272);
        getContentPane().add(bgl);

        Events e = new Events();
        startButton.addActionListener(e);
        helpButton.addActionListener(e);
    }

    public class Events implements ActionListener {


        public void actionPerformed(ActionEvent e) {

            if (e.getSource() == startButton) {
               label.setText("Searching");

               try {
                Unfollow();
            } catch (InterruptedException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }
            }
            else if (e.getSource() == helpButton){
                System.out.println("gottem");
                bgi = new ImageIcon(getClass().getResource("tu2.png"));
            bgl = new JLabel (bgi);
            }
    }

    }

Answer 1

bgl = new JLabel (bgi);

Here you're creating a new JLabel, and putting it into the bgl variable but are doing anything with it and make no change to the JLabel object that continues to be shown in the GUI. It's a common newbie trap to think that by changing the reference of a variable you change the state of the original object that the variable previously referred to. That's not how it works. In other words, the original JLabel that was held by the bgl variable still exists and still displays its original content in the GUI despite this code above. What you should do instead is to change the icon shown by the original JLabel, or in other words, change the state of the current JLabel object, not change references held by the bgl variable. ie,

bgl.setIcon(bgi);

Also, you'll want to get rid of any and all use of null layout and calls to setBounds(...) as this will lead to buggy hard to maintain and upgrade code. Let the layout managers do the heavy lifting with regards to laying out the GUI.