Reputation: 111

Number and loop issue

I am new to programming and am having difficulty with this problem. I am trying to build a wall based on the number entered in the JTextField but the number cannot exceed 20. I cannot get my error message to display nor can I get my brick wall to build. Could someone please help me figure out what I am doing wrong?

public class Wall extends JApplet implements ActionListener {

JTextField enter;
Boolean submit;
JLabel bricks;
JButton build;
JPanel top;
Image zombie;
int value;

public void init() {
    setLayout(new BorderLayout());

    top = new JPanel();
    build = new JButton("AHHHHHH...ZOMBIES!");                          //button for building wall
    bricks = new JLabel("Enter between 1 & 20 rows to contruct:");
    enter = new JTextField(2);

    top.add(build);         //add zombie button
    top.add(bricks);        //add intructions
    top.add(enter);         //add text field
    add(top, BorderLayout.NORTH);


    build.addActionListener(this);


}

public void actionPerformed(ActionEvent ae) {
    if (ae.getSource() == build) {
        int value = Integer.parseInt(build.getText());
        if (value > 0 && value < 21) {
            submit = true;
            repaint();
        } else {
            submit = false;
            repaint();
        }

    }
}

public void paint(Graphics g) {
    super.paint(g);

    //add zombie image
    Image zombie = getImage(getCodeBase(), "Zombie.jpg");
    g.drawImage(zombie, 0, 45, this);

    if (submit = false) //add error message
    {
        g.setColor(Color.WHITE);
        g.setFont(new Font("TimesRoman", Font.BOLD, 40));
        g.drawString("You must enter a number between 1 & 20!", 400, 100);  //add message
    }

    int brick_width = 50;
    int brick_height = 20;
    int spacing = 1;
    int x = 0;
    while (x < 21) {
        drawBrick(g, nextInt(brick_width + spacing), nextInt(brick_height + spacing));
        x = x + getWidth() + 50;
        x = x - 25 + getWidth() + 50;
        x++;

    }

}

public void drawBrick(Graphics g, int x, int y) {
    g.setColor(new Color(150, 0, 0));
        g.fillRect(0, 635, 50, 20);
    }
}

Upvotes: 4

Answers (5)

Sashi Kant

Reputation: 13465

Two issues:

1) Your submit variable is not initialized, you should initialize it to true/false. If you dont want to initialize it, you can simple try with

if(submit!=null && !submit)

2) Secondly, "=" is used for assigning a value where as "==" is used for comparing Change

if (submit = false) //add error message
    {
        g.setColor(Color.WHITE);
        g.setFont(new Font("TimesRoman", Font.BOLD, 40));
        g.drawString("You must enter a number between 1 & 20!", 400, 100);  //add message
    }

if (submit == false) //add error message
    {
        g.setColor(Color.WHITE);
        g.setFont(new Font("TimesRoman", Font.BOLD, 40));
        g.drawString("You must enter a number between 1 & 20!", 400, 100);  //add message
    }

Upvotes: 0

Braj

Reputation: 46841

Instead of painting on top-level containers such as JApplet directly, you have to use JPanel and paint on it. Just override paintComponent() method of JPanel(). Never forget to call super.paintComponent(g) in overridden method.

sample code:

top = new JPanel() {
    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        ...
        // your custom painting code goes here
    }
};

Note:

submit == false and !submit are the correct way to check it but it still will result in NullPointerException because you have never initialized instance variable submit.

Use primitive boolean instead of Boolean to avoid such exception or initialize it properly.