给出三个点如何画弧？

Question

需要代码，谢谢！

Answer 1

这是我写的一个画三次Beizer曲线的代码
有4个控制点
你只要换成2次Beizer曲线就可以了
2次Beizer曲线要3个控制点public class JBeizer extends JOpenShape {
    
    CubicCurve2D.Double c2d = new CubicCurve2D.Double();
    
    /** Creates a new instance of JBeizer */
    public JBeizer(int x, int y) {
        setStartPoint(x, y);
        c2d.ctrlx1 = c2d.ctrlx2 = c2d.x2 = x;
        c2d.ctrly1 = c2d.ctrly2 = c2d.y2 = y;
        this.locationX = x; this.locationY = y;     //设置位置
    }
    
    public void setStartPoint(int x, int y) {
        c2d.x1 = x;
        c2d.y1 = y;
    }
    
    public void setNewPoint(int x, int y, int i) {
        switch (i) {
            case 1:
                c2d.x2 = c2d.ctrlx1 = c2d.ctrlx2 = x;
                c2d.y2 = c2d.ctrly1 = c2d.ctrly2 = y;
                break;
            case 2:
                c2d.ctrlx1 = c2d.ctrlx2 = x;
                c2d.ctrly1 = c2d.ctrly2 = y;
                break;
            case 3:
                c2d.ctrlx2 = x;
                c2d.ctrly2 = y;
                break;
        }
    }
        public void drawShape(Graphics2D g2d) {
        g2d.setColor(this.shapeColor);
        g2d.setStroke(this.sStr);
        g2d.draw(c2d);
    }
}

Answer 2

这个要配合mouseClicked事件
以下代码是我里面的一部分if (JShape.typeId == JShape.TYPE_BEIZER) {
                    currentShape.setNewPoint(evt.getX(), evt.getY(), clickCount);
                    clickCount++;
                    if (clickCount > 3) {
                        isFirstClick = true;
                        currentShape.setShapeColor(fatherFrame.penColor);
                        currentShape.setStrokeNum(fatherFrame.lStroke);
                        currentShape.setLineStyle(fatherFrame.lStyle);
                        recover();
                    } 
                }画三次Beizer曲线的二次Beizer曲线的类是 QuadCurve2D
具体用法你就看api吧！
祝你成功！