MouseDrag绘制一个正方形无法正常工作

Question

 @Override
    public Shape getShape() {
        final Rectangle2D.Double result = new Rectangle2D.Double();
        result.setFrameFromDiagonal(getStart(), getEnd());
        //FIX this is causing square to move when going opposite direction  
        result.setRect(result.getX(), result.getY(),
                       result.getHeight(), result.getHeight());
        return result;
    }

So here is my code that is drawing a square using Rectangle2D.Double. The getStart() and getEnd() are points that are being returned from mouseDrag events. When I drag to the right or up, it works as intended and creates a square. When I drag left or down the square moves with the drag as it draws. I am fairly new to Java swing and paint components. Wondering if anyone know what is causing this and why?

Answer 1

You need to consider a few specialities:

1. Save the first coordinate on mouse click: x,y
2. Save the last coordinate on mouse drag x2,y2
3. Set min x and y coordinates as the startpoint for setRect: Math.min(x,x2);
4. Use the absolute value of the coordinate difference to calculate the height and width of rectangle: Math.abs(x-x2);

---

px = Math.min(x,x2);
int py = Math.min(y,y2);
int pw=Math.abs(x-x2);
int ph=Math.abs(y-y2);
result.setRect(px, py, pw, ph);