Swing 中的自由手线 - 摆脱错误"index out of bound Exception"

Question

我必须在jframe中绘制鼠标线。这是我的方法PaintComponent：

public void paintComponent(Graphics g){
 Graphics2D g2d = (Graphics2D) g;
 if(pointCollection.get(0)!=null && pointCollection.get(pointCollection.size())!=null){
  g2d.setPaint(Color.BLUE);
  g2d.setStroke(new BasicStroke(1.5f));
  g2d.draw(line2d);
 }
}

基于我从接口MouseMotionListener和Mouselistener的实现方法。

public void mouseDragged(MouseEvent arg0) {
pointCollection = new ArrayList<Point>(50);
pointCollection.add(arg0.getPoint());
  for (int index = 0; index < pointCollection.size(); index++){
    line2d=new Line2D.Double(pointCollection.get(index), pointCollection.get(index+1));
   //repaint();
  }
 }

这个想法是将点和绘制在它们之间的线上的序列，以便我得到弯曲的线，而不是直线。您能帮我找出我正在做的合乎逻辑的错误吗？

谢谢！

Answer 1

您要超越集合的末端。

public void mouseDragged(MouseEvent arg0) {
  for (int index = 0; index < (pointCollection.size() - 1); index++){
    line2d=new Line2D.Double(pointCollection.get(index), 
        pointCollection.get(index + 1));
   //repaint();
  }

}