Android 几何图形工具类GeometryUtil

package com.android.imooc.goo;

import android.graphics.PointF;

/**
* 几何图形工具
*/
public class GeometryUtil {

/**
* As meaning of method name. 获得两点之间的距离
*
* @param p0
* @param p1
* @return
*/
public static float getDistanceBetween2Points(PointF p0, PointF p1) {
float distance = (float) Math.sqrt(Math.pow(p0.y - p1.y, 2) + Math.pow(p0.x - p1.x, 2));
return distance;
}

/**
* Get middle point between p1 and p2. 获得两点连线的中点
*
* @param p1
* @param p2
* @return
*/
public static PointF getMiddlePoint(PointF p1, PointF p2) {
return new PointF((p1.x + p2.x) / 2.0f, (p1.y + p2.y) / 2.0f);
}

/**
* Get point between p1 and p2 by percent. 根据百分比获取两点之间的某个点坐标
*
* @param p1
* @param p2
* @param percent
* @return
*/
public static PointF getPointByPercent(PointF p1, PointF p2, float percent) {
return new PointF(evaluateValue(percent, p1.x, p2.x), evaluateValue(percent, p1.y, p2.y));
}

/**
* 根据分度值，计算从start到end中，fraction位置的值。fraction范围为0 -> 1
*
* @param fraction
* @param start
* @param end
* @return
*/
public static float evaluateValue(float fraction, Number start, Number end) {
return start.floatValue() + (end.floatValue() - start.floatValue()) * fraction;
}

/**
* Get the point of intersection between circle and line. 获取
* 通过指定圆心，斜率为lineK的直线与圆的交点。
*
* @param pMiddle
*            The circle center point.
* @param radius
*            The circle radius.
* @param lineK
*            The slope of line which cross the pMiddle.
* @return
*/
public static PointF[] getIntersectionPoints(PointF pMiddle, float radius, Double lineK) {
PointF[] points = new PointF[2];

float radian, xOffset = 0, yOffset = 0;
if (lineK != null) {
radian = (float) Math.atan(lineK);
xOffset = (float) (Math.sin(radian) * radius);
yOffset = (float) (Math.cos(radian) * radius);
} else {
xOffset = radius;
yOffset = 0;
}
points[0] = new PointF(pMiddle.x + xOffset, pMiddle.y - yOffset);
points[1] = new PointF(pMiddle.x - xOffset, pMiddle.y + yOffset);

return points;
}
}