Android之2D图形(圆、直线、点)工具类 （持续更新）
16lz
2021-01-23
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;}}
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