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Thread: What's wrong with my code

  1. #1
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    Default What's wrong with my code

    package Enrollment;
     
    import java.awt.*;
    import java.awt.event.*;
    import javax.swing.*;
     
     
    public class Login extends JFrame{
     
        public String name;
        JTextField txtUsername;
     
        public Login(){
     
            setLayout(new FlowLayout());
            txtUsername = new JTextField(" ", 10);
            add(txtUsername);
     
            JButton btnLogin = new JButton("Login");
            add(btnLogin);
     
            btnLogin.addActionListener(new ButtonListener());
        }
     
        private class ButtonListener implements ActionListener{
            @Override
              public void actionPerformed(ActionEvent e){
     
               if(name == txtUsername.getText()){
                    Student StudentRegistration = new Student();
                    StudentRegistration.run();
                    StudentRegistration.lblName.setText(name);
                    dispose();
               };
     
     
            }
     
        }
     
        public void run(){
            setTitle("Login");
            setBounds(200,200,350,200);
            setVisible(true);
            setResizable(false);
            setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        }
    }
    package Enrollment;
     
    import java.awt.*;
    import java.awt.event.*;
    import javax.swing.*;
     
    public class Student extends JFrame {
     
        Container con = null;
        JLabel picStudent;
        JLabel lblName;
     
        public Student(){
     
            con = getContentPane();
            con.setLayout(null);
     
            ImageIcon imh = new ImageIcon(getClass().getResource("Images/bg.jpg"));
            Icon studpic = new ImageIcon(getClass().getResource("Images/studpic.jpg"));
            setSize(imh.getIconWidth(), imh.getIconHeight());
     
             JPanel panel = new JPanel(){
                 @Override
                public void paintComponent(Graphics g) 
                {
                    Image imh = new ImageIcon("Images/bg.jpg").getImage();
                    Dimension size = new Dimension(imh.getWidth(null), imh.getHeight(null));
                    setPreferredSize(size);
                    setMinimumSize(size);
                    setMaximumSize(size);
                    setSize(size);
                    setLayout(null);
                    g.drawImage(imh, 0, 0, null);
                } 
             };
             con.add(panel);
             panel.setBounds(0, 0, imh.getIconWidth(), imh.getIconHeight());
             JPanel panelcontent = new JPanel(new FlowLayout());
             panelcontent.setBounds(0,0,200,200);
             panel.add(panelcontent);
             picStudent = new JLabel(studpic);
             lblName = new JLabel();
             panelcontent.add(picStudent);
             panelcontent.add(lblName);
    }
     
        public void run(){
     
             setTitle("Student Registration");
             setBounds(0,0,575,431);
             setVisible(true);
             setResizable(false);
             setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
     
        }
    }
    package Enrollment;
     
     
    public class Main {
        public static void main(String[] args){
     
            Login login = new Login();
            login.run();
     
     
     
     
        }
     
     
    }
    this is my error output
    Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at javax.swing.ImageIcon.<init>(ImageIcon.java:205)
    at Enrollment.Student.<init>(Student.java:19)
    at Enrollment.Login$ButtonListener.actionPerformed(Lo gin.java:29)
    at javax.swing.AbstractButton.fireActionPerformed(Abs tractButton.java:2018)


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: What's wrong with my code

    At line 19 there is a variable or value returned by a method with a null value. Find the variable or method and backtrack to find out why its value is null.

    Does the image file exist at the location referred to by the code?
    If you don't understand my answer, don't ignore it, ask a question.

  3. #3
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    Default Re: What's wrong with my code

    Yes, all of my image file is at the right location.

  4. #4
    Super Moderator Norm's Avatar
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    Default Re: What's wrong with my code

    image file is at the right location.
    What does this method call return?
    getClass().getResource("Images/bg.jpg")
    If it returns null then the image is not in the correct location.
    Be sure to test the value for all images.
    Last edited by Norm; September 26th, 2012 at 09:11 AM.
    If you don't understand my answer, don't ignore it, ask a question.

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