How to recursively draw lines in Java?

Question

I have a project i am struggling to get started with, the core of it is around drawing lines recursively perpendicular to one another. I am rather terrible at GUIs for a start. This is what i have so far but i don't know how to implement a recursive method that will draw the lines. This is what i have so far, just simple code to draw a line:

import java.awt.Graphics;
import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.*;
import java.awt.geom.*;

public class Test extends JPanel{
    private static String n;
    private static String r;

    public static void main(String[] args){
        //n = args[0];
        //r = args[1];
        //System.out.println("THIS IS MY N: " + n);
        //System.out.println("THIS IS MY R: " + r);
        JFrame frame = new JFrame();
        frame.setSize(400, 400);
        frame.add(new Test());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }

    public void paint(Graphics g){
        int nn = 10;
        for(int i = 0; i < nn; i++){
            g.drawLine(400, 200, 50, 250);
        } 
    }
}

So i was thinking along the lines of something like this to do the recursive drawing of the lines:

public static void drawLine(int x1, int y1, int x2, int y2){
 if(count == 20){
  //Stop or some other condition
 }else{
  g.drawLine(x1, y1, x2, y2);
  drawLine(x1+5, y1+5, x2+10, y2+10);
  }
 }

I'm not sure how the paint method actually works into it. I don't think i fully grasp what the paint method is actually doing

I can not see any recursive code. What do you think the functionality of your recursive code would be? — Scary Wombat, Aug 16 '16 at 00:42
I don't have any recursive code as of yet. I would like to know how to create code that would enable me to recursively draw lines. The code above is my initial attempt in just trying to draw a line, i would like to add to it to be able to recursively draw a number of lines — Sam, Aug 16 '16 at 00:44
Sam - You have to think about, what is a recursive method and how would it apply to your request? — Scary Wombat, Aug 16 '16 at 00:48
Ideally it would be a method that would take the 4 parameters of the line and keep calling itself whilst adding the parameters until it had reached a certain count. — Sam, Aug 16 '16 at 01:34
OK, now change your question to show a prototype of this method — Scary Wombat, Aug 16 '16 at 01:51

score 0 · Accepted Answer · edited May 23 '17 at 12:33

The paint() method is the method that is called every time the component is being painted. This will happen initially, when the frame is resized, when the repaint() method is called, etc. In this case you will want to use paintComponent() over paint(). You can save the line as a variable Line2D.Double and use it when you paint.

Example code:

private static Line2D.Double line = new Line2D.Double();
private static int count = 100;

@Override
public void paintComponent(Graphics g){
    super.paintComponent(g);
    // use temp line to not effect original line
    Line2D.Double tempLine = line;
    for (int q = 0; q < count; q++){
        g.drawLine((int)tempLine.x1, (int)tempLine.y1, (int)tempLine.x2, (int)tempLine.y2);
        tempLine = new Line2D.Double(tempLine.x1+5, tempLine.y1+5, 
            tempLine.x2+10, tempLine.y2+10);
    }
}

Awesome! Thank you. So are you storing the line in temp line, drawing it, updating the coordinates while iterating over this process 100 times? — Sam, Aug 16 '16 at 02:52
@Sam yup. Also could you mark this answer as correct so the question is closed — Arthur, Aug 16 '16 at 02:54

How to recursively draw lines in Java?

1 Answers1