Isometric Mouse Camera Panning

Question

I am building an isometric game environemnt and i want to be able to pan the camera around the map by holding the right mouse button, can someone talk me through the logic for this please, i have made an attempt and tried a number ways. I can get the camera to move correctly the first time but when i click and hold the second time the camera resets itself, thanks in advance for any help

import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.Timer;

public class CameraMovementTest extends JPanel{

private Timer timer;
private int DELAY = 10;
private  CustomMouseListener mouseListener;
private int positionX = 0, positionY = 0;

public CameraMovementTest() {

    mouseListener  = new CustomMouseListener();
    this.addMouseListener(mouseListener);
    this.addMouseMotionListener(mouseListener);
    this.setSize(500,500);
    this.setVisible(true);

    //Swing Timer
    timer = new Timer(DELAY, new ActionListener(){
        @Override
        public void actionPerformed(ActionEvent arg0) {
            update();
            repaint();
            validate(); 
        }
    }); 
    timer.start();
}

private void update() {
    if(mouseListener!=null){
        positionX = mouseListener.getX();
        positionY = mouseListener.getY();
    }
}

@Override
public void paint(Graphics g) {
    super.paint(g);
    g.fillRect( positionX,  positionY, 300,300);
}

public class CustomMouseListener implements MouseListener, MouseMotionListener {
    private int positionX = 0, positionY = 0;
    private int mouseClickX, mouseClickY;

    @Override
    public void mousePressed(MouseEvent evt) {

        if(SwingUtilities.isRightMouseButton(evt)) {

            mouseClickX = evt.getX();
            mouseClickY = evt.getY();
        }   
    }
    @Override
    public void mouseDragged(MouseEvent evt) {
        if(SwingUtilities.isRightMouseButton(evt)) {
            positionX = mouseClickX - evt.getX();
            positionY = mouseClickY - evt.getY();
        }
    }
    @Override
    public void mouseMoved(MouseEvent arg0) {}
    @Override
    public void mouseClicked(MouseEvent arg0) { }
    @Override
    public void mouseEntered(MouseEvent arg0) { }
    @Override
    public void mouseExited(MouseEvent arg0) {}

    @Override
    public void mouseReleased(MouseEvent arg0) {}
    public int getX(){
        return positionX;
    }
    public int getY(){
        return positionY;
    }
}


public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
        @Override
        public void run() {
            JFrame f = new JFrame();
            f.setVisible(true);
            f.setSize(new Dimension(500,500));
            f.setContentPane(new CameraMovementTest());
        }
    });
}

}

Answer 1

@Override
public void mouseDragged(MouseEvent evt) {
    if(SwingUtilities.isRightMouseButton(evt)) {
        positionX = mouseClickX - evt.getX();
        positionY = mouseClickY - evt.getY();
    }
}

You're setting the position to the difference between the initial mousedown and the actual position. In this case, what you get is the expected result. What you rather should do is calculate the delta between the actual and the last mouse position and add this delta to the position:

@Override
public void mousePressed(MouseEvent evt) {

    if(SwingUtilities.isRightMouseButton(evt)) {
        mouseClickX = evt.getX();
        mouseClickY = evt.getY();
    }   
}
@Override
public void mouseDragged(MouseEvent evt) {
    if(SwingUtilities.isRightMouseButton(evt)) {
        int deltaX = mouseClickX - evt.getX();
        int deltaY = mouseClickY - evt.getY();
        mouseClickX = evt.getX();
        mouseClickY = evt.getY();
        positionX += deltaX;
        positionY += deltaY;
    }
}

(You might need to fix the direction by replacing the += with -=)