Android之2D图形(圆、直线、点)工具类

    public class Circle {            private PointF centerPoint;            private float radius;            public PointF getCenterPoint() {                return centerPoint;            }            public void setCenterPoint(PointF centerPoint) {                this.centerPoint = centerPoint;            }            public float getRadius() {                return radius;            }            public void setRadius(float radius) {                this.radius = radius;            }                                }  

    public class CircleUtils {                    /**            * 根据圆上的三个点求圆心坐标、半径            * @param pA            * @param pB            * @param pC            * @return            */            public static Circle getCircle(PointF pA,PointF pB,PointF pC)            {                 float mat1,mat2,mat3 ;                   mat1 = ((pB.x*pB.x +pB.y*pB.y)-(pA.x*pA.x +pA.y*pA.y))*(2*(pC.y-pA.y))-                           ((pC.x*pC.x +pC.y*pC.y)-(pA.x*pA.x +pA.y*pA.y))*(2*(pB.y-pA.y));                   mat2 = (2*(pB.x-pA.x))*((pC.x*pC.x+pC.y*pC.y)-(pA.x*pA.x +pA.y*pA.y))-                           (2*(pC.x-pA.x))*((pB.x*pB.x+pB.y*pB.y)-(pA.x*pA.x +pA.y*pA.y));                   mat3 = 4*((pB.x-pA.x)*(pC.y-pA.y) - (pC.x-pA.x)*(pB.y-pA.y));                                    Circle circle=new Circle();                 PointF centerPoint=new PointF();                 float radius;                 centerPoint.x = mat1/mat3;                   centerPoint.y = mat2/mat3;                  radius=(float) Math.sqrt(((pA.x-centerPoint.x)*(pA.x-centerPoint.x) + (pA.y-centerPoint.y)*(pA.y-centerPoint.y)));                                    circle.setCenterPoint(centerPoint);                 circle.setRadius(radius);                                  return circle;            }                        /**            * 求一段圆弧两端另一点的坐标            * @param circle            * @param startP 圆弧一端的点            * @param angle 圆弧对应的角度            * @return            */            public PointF getEndPointOfArc(Circle circle,PointF startP,float angle) {                PointF centerP=circle.getCenterPoint();                PointF endPointF=new PointF();                endPointF.x=(float) (centerP.x+(startP.x-centerP.x)*Math.cos(angle*Math.PI/180)-(startP.y-centerP.y)*Math.sin(angle*Math.PI/180));                endPointF.y=(float) (centerP.y+(startP.x-centerP.x)*Math.sin(angle*Math.PI/180)+(startP.y-centerP.y)*Math.cos(angle*Math.PI/180));                return endPointF;                            }        }