Need help making my images drag more smoothly

Question

I'm trying to learn how to use the java2d api and I'm having a rough go of it.
Currently, the following code should populate a jframe's container with some jcomponent's called 'card' (which basically draw a given image as a texture over a specified rectangle). Then you should be able to drag them around. Sounds simple enough. I've finally gotten it to a point that's almost work-able, but there are two problems:
1) the last card added ignores it's location (via setBounds) until you start dragging it.
2) I'm not sure what kind of math is necessary in order to make dragging the entire JComponent a smooth process (Moving just the rectangle presents it's own weird oddities which I'll expound upon if you ask, but it is smooth).
Here's the code:
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.*;
import javax.imageio.ImageIO;
import javax.swing.*;
public class test
        public static void main(String[]args)throws IOException
                String path1 = "card1.jpg";
                String path2 = "card2.jpg";
                String path3 = "card3.jpg";
                String path4 = "card4.jpg";
                card one = new card(path1, 40, 40);
                card two = new card(path2, 300, 300);
                card three = new card(path3, 50, 400);
                card four = new card(path4, 500, 100);
                JFrame f = new JFrame();
                f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                f.getContentPane().add(one);
                f.getContentPane().add(two);
                f.getContentPane().add(three);
                f.getContentPane().add(four);
                f.setSize(1000, 1000);
                f.setVisible(true);
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.awt.image.BufferedImage;
import javax.imageio.ImageIO;
import javax.swing.*;
public class card extends JComponent implements MouseListener,
        MouseMotionListener
        BufferedImage image;
        Rectangle rect;
        double lastX;
        double lastY;
        double distX = 0;
        double distY = 0;
        int w = 205;
        int h = 280;
        public card(String path, int x, int y)throws IOException
                image = ImageIO.read(new File(path));
                setBounds(x, y, w, h);
                rect = new Rectangle(0, 0, w, h);
                lastX = x;
                lastY = y;
                addMouseListener(this);
                addMouseMotionListener(this);
        protected void paintComponent(Graphics g)
                super.paintComponent(g);
                g.drawImage(image, rect.x, rect.y, this);
        public void mouseClicked(MouseEvent e)
        public void mouseEntered(MouseEvent e) {}
        public void mouseExited(MouseEvent e) {}
        public void mousePressed(MouseEvent e)
                if(rect.contains(e.getPoint()))
                        distX = e.getX() - lastX;
                        distY = e.getY() - lastY;
        public void mouseReleased(MouseEvent e) {}
        public void mouseDragged(MouseEvent e)
                Point p = e.getPoint();
                if(rect.contains(p))
                        lastX+=(e.getX() - lastX) - distX;
                        lastY+=(e.getY() - lastY) - distY;
                        this.setBounds((int)lastX, (int)lastY, w, h);
                        //rect.setLocation((int)lastX, (int)lastY);
                        repaint();
        public void mouseMoved(MouseEvent e)
                //if(rect.contains(e.getPoint()))
                        //System.out.println("inside");
}

Answer 1

Think about object-oriented programming (OOP) ideas. A Card can know about itself, things
like its color, suit, value. But it cannot know where it is on a card table without asking
the table (its parent). Like Newton's man_in_a_box illustration, it cannot know how to
orient or move in its outer environment. The table/parent component is the one who knows
where cards are and is therefore the logical one to have mouse code for moving them.
import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.io.*;
import javax.imageio.ImageIO;
import javax.swing.*;
public class CardDragTest implements MouseListener,
        MouseMotionListener
        CardDrag[] cards;
        CardDrag selectedCard;
        Point offset = new Point();
        boolean dragging = false;
        int selectedIndex = -1;
        public void mouseClicked(MouseEvent e) {}
        public void mouseEntered(MouseEvent e) {}
        public void mouseExited(MouseEvent e) {}
        public void mousePressed(MouseEvent e)
                Point p = e.getPoint();
                for(int j = 0; j < cards.length; j++)
                        Rectangle r = cards[j].getBounds();
                        if(r.contains(p))
                                offset.x = p.x - r.x;
                                offset.y = p.y - r.y;
                                selectedCard = cards[j];
                                dragging = true;
                                break;
        public void mouseReleased(MouseEvent e)
                dragging = false;
        public void mouseDragged(MouseEvent e)
                Point p = e.getPoint();
                if(dragging)
                        Rectangle r = selectedCard.getBounds();
                        int x = p.x - offset.x;
                        int y = p.y - offset.y;
                        selectedCard.setLocation(x, y);
                        selectedCard.repaint();
        // Use selectedIndex member variable to keep
        // this method from working too hard.
        public void mouseMoved(MouseEvent e)
                Point p = e.getPoint();
                boolean hovering = false;
                for(int j = 0; j < cards.length; j++)
                        Rectangle r = cards[j].getBounds();
                        if(r.contains(p))
                                hovering = true;
                                if(selectedIndex != j)
                                        System.out.println("selectedIndex = " + j);
                                        selectedIndex = j;
                                break;
                if(!hovering && selectedIndex != -1)
                     System.out.println("reset selectedIndex");
                     selectedIndex = -1;
        public static void main(String[]args) throws IOException
                CardDragTest test = new CardDragTest();
                String path1 = "playingCards/1.jpg";
                String path2 = "playingCards/2.jpg";
                String path3 = "playingCards/3.jpg";
                String path4 = "playingCards/4.jpg";
                CardDrag one = new CardDrag(path1, 40, 40);
                CardDrag two   = new CardDrag(path2, 300, 300);
                CardDrag three = new CardDrag(path3, 50, 400);
                CardDrag four  = new CardDrag(path4, 500, 100);
                test.cards = new CardDrag[] { one, two, three, four };
                JFrame f = new JFrame();
                f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                Container cp = f.getContentPane();
                cp.addMouseListener(test);
                cp.addMouseMotionListener(test);
                cp.setLayout(null);
                cp.add(one);
                cp.add(two);
                cp.add(three);
                cp.add(four);
                f.setSize(600, 500);
                f.setVisible(true);
class CardDrag extends JComponent
        BufferedImage image;
        public CardDrag(String path, int x, int y)throws IOException
                image = ImageIO.read(new File(path));
                int w = image.getWidth();
                int h = image.getHeight();
                setBounds(x, y, w, h);
        protected void paintComponent(Graphics g)
                super.paintComponent(g);
                g.drawImage(image, 0, 0, this);
}