Graphics line turning on centre point

[beforetheyknew]

Hi guys I'm trying to learn animation/graphics(they're synonymus to me) what would really help me is a working model of a line turning on an intersection. I've searched around and all i can find is clocks and stuff but all i want is the basic code to cause a line to turn on a centre(like a single clock hand). I just want to learn motion from it, a working code would be massively appreciated. Thanks in advance.

[Ezzaral]

Ok, here's something to play with

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;

public class LinePanel extends JPanel {

    Timer animationTimer;
    float angle = 0f;
    int lineLen = 60;
    int x = 20;
    int y = 20;
    int moveX = 2;
    int moveY = 2;
    double angleChange = Math.PI/20;

    public LinePanel() {
        animationTimer = new Timer(50, new LineAnimation());
        animationTimer.start();
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D)g;
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

        double dx = Math.cos(angle) * lineLen;
        double dy = Math.sin(angle) * lineLen;
        g2d.clearRect(0, 0, getWidth(), getHeight());
        g2d.setColor(Color.BLUE);
        g2d.drawLine((int)(x - dx), (int)(y + dy), (int)(x + dx), (int)(y - dy));
    }

    class LineAnimation implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            angle += angleChange;
            x += moveX;
            y += moveY;
            if (x < 0 || x > getWidth()) {
                moveX *= -1;
                angleChange *= -1;
            }
            if (y < 0 || y > getHeight()) {
                moveY *= -1;
                angleChange *= -1;
            }
            repaint();
        }
    }

    public static void main(String[] args) {
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(new LinePanel());
        f.setBounds(100, 100, 300, 300);
        f.setVisible(true);
    }
}

[beforetheyknew]

Haha m8 that is fantastic, see even that is to advanced for me i cant get it to stay still!

[beforetheyknew]

So how do i get that to turn as if one side was pinned down? like a clock, seriously i cant do it not even from that code, I really hate graphics it doesnt make any sense to me.

[Ezzaral]

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;

public class LinePanel2 extends JPanel {

    Timer animationTimer;
    int lineLen = 50;   // length of the line
    int x = 65;    // x anchor
    int y = 65;    // y anchor
    float angle = 0f;   // angle of the line
    double angleChange = Math.PI/20;    // rotation per tick

    public LinePanel2() {
        // start the timer firing every 50ms
        animationTimer = new Timer(50, new LineAnimation());
        animationTimer.start();
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D)g;
        // this just makes the line look smoother, less pixelation when at an angle
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

        // calc the x and y offsets based on the current angle and line length
        double dx = Math.cos(angle) * lineLen;
        double dy = Math.sin(angle) * lineLen;
        // clear the area and draw the line
        g2d.clearRect(0, 0, getWidth(), getHeight());
        g2d.setColor(Color.BLUE);
        g2d.drawLine(x, y, (int)(x + dx), (int)(y - dy));
    }

    class LineAnimation implements ActionListener {
        // this gets called every "tick" of the timer
        public void actionPerformed(ActionEvent e) {
            // change angle and repaint
            // subtracting for clockwise motion
            angle -= angleChange;
            repaint();
        }
    }

    public static void main(String[] args) {
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(new LinePanel2());
        f.setBounds(100, 100, 200, 200);
        f.setVisible(true);
    }
}

[beforetheyknew]

Dude seriously i couldn't be more greatful. Thank you so much I've spent ages looking at so much stuff on animation and i really get that. Seriously I cant thank you enough, you rock!