Question

I am not sure why my code is not working but it is driving me crazy.

This is my class that should draw the button and creates the area to draw on:

The second set of code is the driver program I need to make 4 canvas’s that when I make two mouse clicks it draws a line between the two clicks and then repaints if I try and click on a canvas again.

I get the following errors:
error: invalid method declaration; return type required
addMouseListener(this);
^
error: illegal start of type
addMouseListener(this);
^

public class Scribble extends JPanel implements MouseListener
{
addMouseListener(this);
int x, x1, y, y1;
boolean flag = false;

protected void paintComponent(Graphics g) {
    super.paintComponent(g);

    g.drawLine(x, y, x1, y1);
}


public void mouseReleased(MouseEvent e)
{

    if (!flag){
        x = e.getX();
        y = e.getY();
        flag = true;
    }
    else{
        x1 = e.getX();
        y1 = e.getY();
        flag = false;
        repaint();
}
}



public void mouseExited(MouseEvent e){}
public void mouseClicked(MouseEvent e){}
public void mousePressed(MouseEvent e){}
public void mouseMoved(MouseEvent e){}
public void mouseEntered(MouseEvent e){}

}



public class Lab8Draw extends JFrame{

public Lab8Draw(){
    Color c = new Color(100, 10, 200);
    setTitle("Lab 8 - Application #1");
    setLayout(new GridLayout(2,2));
    Scribble s = new Scribble();
    s.setBackground(Color.WHITE);
    add(s);
    Scribble s1 = new Scribble();
    s1.setBackground(Color.RED);
    add(s1);
    Scribble s2 = new Scribble();
    s2.setBackground(c);
    add(s2);
    Scribble s3 = new Scribble();
    s.setBackground(Color.BLUE);
    add(s3);

}


    public static void main (String[] args){


        Lab8Draw frame = new Lab8Draw();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(800, 800);
        frame.setVisible(true);
    }
}

Answer 1

You will have to implement MouseListener

public class Scribble extends JPanel implements MouseListener

and register it

Scribble s = new Scribble();
s.addMouseListener(s);

The Java tutorials provide a useful guide to writing a MouseListener.

Alternatively, you could define an inner class that extends MouseInputAdapter as it already has empty implementations of the MouseListener methods.