Swing GUI in Eclipse

Question

I'm trying to create a Swing GUI in Eclipse by following the guide in Oracle's documentation. However, they use Netbeans in the tutorial and I believe that might be the cause of the problem.

I've tried to create a temperature converter but the label for the fahrenheit number is repeatedly complaining that it cannot be resolved. Here is the source code:

private JPanel contentPane;
private JTextField tempTextField; // Not sure if I need the other components here as well?
                                  // Could be needed in order to be used in the 
                                  // actionPerformed method.

...

JButton convertButton = new JButton("Convert");
    convertButton.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent arg0) {
            //Parse degrees Celsius as a double and convert to Fahrenheit.
            int tempFahr = (int)((Double.parseDouble(tempTextField.getText()))
                    * 1.8 + 32);
            fahrenheitLabel.setText(tempFahr + " Fahrenheit"); // fahrenheitLabel is what's 
        }                                                     //highlighted in Eclipse.
    });
    convertButton.setBounds(6, 38, 134, 29);
    contentPane.add(convertButton);

    JLabel fahrenheitLabel = new JLabel("Fahrenheit");
    fahrenheitLabel.setBounds(152, 43, 78, 16);
    contentPane.add(fahrenheitLabel);

The link to the Oracle documentation is here: http://docs.oracle.com/javase/tutorial/uiswing/learn/creatinggui.html

I should point out the error persists even when fahrenheitLabel is declared prior to the method - so it definitely can't be the ordering of the code that matters (I think).

If it's anything to do with the components having incorrect names I would be surprised, but here is a screenshot:

Many thanks to anyone who can give suggestions on the matter!

EDIT: Thank you to those who have already given suggestions to fiddle with the ordering of the code. However, it then tells me I need to make the fahrenheitLabel final, which I would have thought conflicts with the ability to dynamically change upon the user entering different inputs.

EDIT 2: Apparently making the variable final is valid. Thank you to all for your suggestions.

Answer 1

Of course it doesnt know the label, because you declare it after the method. Try putting

JLabel fahrenheitLabel = new JLabel("Fahrenheit");

before

convertButton.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent arg0) {
        //Parse degrees Celsius as a double and convert to Fahrenheit.
        int tempFahr = (int)((Double.parseDouble(tempTextField.getText()))
                * 1.8 + 32);
        fahrenheitLabel.setText(tempFahr + " Fahrenheit"); // fahrenheitLabel is what's 
    }                                                     //highlighted in Eclipse.
});

Answer 2

public class SimpleDemo extends JFrame {

    JLabel jLabel = new JLabel("Changing label");
    JButton button = new JButton("Click");
    static int i = 0;



    public SimpleDemo() {
            // TODO Auto-generated constructor stub
            this.setSize(500, 500);

            this.add(button);
            this.add(jLabel);
            this.setLayout(new FlowLayout(2, 2, 2));
            this.setVisible(true);
            this.setDefaultCloseOperation(EXIT_ON_CLOSE);

            button.addActionListener(new ActionListener() {

                @Override
                public void actionPerformed(ActionEvent e) {

                    // TODO Auto-generated method stub
                    jLabel.setText("Changed Text" + i++);

                }
            });
        }

        public static void main(String args[]) {
            System.out.println("Woring fine********");
            SimpleDemo demo = new SimpleDemo();

        }
    }

Check this one might be useful to u.