Getting the (starting) X and Y coordinates of a Path2D shape drawn on Jpanel

Question

So, I have a program where I can add shapes to JPanel using Path2D objects and then I can click and drag them around. What I want to do is be able to find the final X and Y

Answer 1

Before you can do anything, you need to know the offset of the mouse click from the corner of the shape, this will allow you to drag the object so it doesn't suddenly "jump" to your current mouse position...

@Override
public void mousePressed(MouseEvent e) {
    //...
    for (Shape shape : myShapes) {
            //...
            this.point = e.getPoint();
            int deltaX = point.x - shape.getBounds().x;
            int deltaY = point.y - shape.getBounds().y;
            offset = new Point(deltaX, deltaY);
            //...
        }
    }
}

Then, you would calculate the delta of change, between the current mouse position and the offset. Because you're applying a translate, you also need to subtract the shape's current location, as the translation is based on the shape's current location and we only want to apply the amount of change

@Override
public void mouseDragged(MouseEvent e) {
    if (pressed) {
        int index = myShapes.indexOf(clickedShape);
        myShapes.remove(index);

        int deltaX = e.getPoint().x - offset.x;
        int deltaY = e.getPoint().y - offset.y;

        clickedShape = new Path2D.Double(clickedShape,
                        AffineTransform.getTranslateInstance(
                                        deltaX - clickedShape.getBounds().x,
                                        deltaY - clickedShape.getBounds().y));
        myShapes.add(index, clickedShape);
        point = e.getPoint();
        repaint();
    }
}

Now, having said all that, don't do this...

protected void paintComponent(Graphics g) {
    //...
    this.setOpaque(true);
    this.setBackground(Color.WHITE);

Changing the state of the component from within the paint method can setup a infinite loop of repaint requests, which can chock your system. Also, the changes you make won't be applied to the current graphics context, as these properties are generally applied by the paint method...

And a working copy....

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.RenderingHints;
import java.awt.Shape;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.AffineTransform;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Path2D;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

class Canvas extends JPanel {

    private static final long serialVersionUID = 1L;

    private boolean drawing;
    private List<Shape> myShapes = new ArrayList<Shape>();

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new Canvas());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public Canvas() {
        MyMouseAdapter myMouseAdapter = new MyMouseAdapter();
        addMouseListener(myMouseAdapter);
        addMouseMotionListener(myMouseAdapter);
        addSquare(100, 100);
    }

    @Override
    public Dimension getPreferredSize() {
        return new Dimension(400, 400);
    }

    public void setList(ArrayList<Shape> shapes) {

    }

    public List<Shape> getList() {
        return null;
    }

    public void addSquare(int width, int height) {
        Path2D rect2 = new Path2D.Double();
        rect2.append(new Rectangle(getWidth() / 2 - width / 2, getHeight() / 2
                        - height / 2, width, height), true);

        myShapes.add(rect2);
        repaint();
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;
        g2.setStroke(new BasicStroke(2));
        for (Shape shape : myShapes) {
            g2.draw(shape);
        }
    }

    class MyMouseAdapter extends MouseAdapter {

        private boolean pressed = false;
        private Point point;
        private Point offset;
        private Shape clickedShape;

        @Override
        public void mousePressed(MouseEvent e) {
            if (e.getButton() != MouseEvent.BUTTON1) {
                return;
            }
            for (Shape shape : myShapes) {
                if (shape != null
                                && shape.contains(e.getPoint())) {
                    System.out.println("Clicked");
                    pressed = true;
                    clickedShape = shape;
                    this.point = e.getPoint();
                    int deltaX = point.x - shape.getBounds().x;
                    int deltaY = point.y - shape.getBounds().y;
                    offset = new Point(deltaX, deltaY);
                    System.out.println(point + "x" + offset);
                    repaint();
                    break;
                }
            }
        }

        @Override
        public void mouseDragged(MouseEvent e) {
            if (pressed) {
                int index = myShapes.indexOf(clickedShape);
                myShapes.remove(index);

                int deltaX = e.getPoint().x - offset.x;
                int deltaY = e.getPoint().y - offset.y;

                clickedShape = new Path2D.Double(clickedShape,
                                AffineTransform.getTranslateInstance(
                                                deltaX - clickedShape.getBounds().x,
                                                deltaY - clickedShape.getBounds().y));
                myShapes.add(index, clickedShape);
                point = e.getPoint();
                repaint();
            }
        }

        @Override
        public void mouseReleased(MouseEvent e) {
            offset = null;
            pressed = false;
        }
    }
}