点在圆内 [英] Point within circle

问题描述

给定圆的中心点和半径，如何知道某个点（x，y）是否在圆中？任何人都知道？感谢。

Given the center point and radius of a circle, how do I know if a certain point (x,y) is in the circle? Anyone knows it? Thanks.

推荐答案

最初你问Objective-C。

Originally you asked for Objective-C.

CGFloat DistanceBetweenTwoPoints(CGPoint point1,CGPoint point2)
{
    CGFloat dx = point2.x - point1.x;
    CGFloat dy = point2.y - point1.y;
    return sqrt(dx*dx + dy*dy );
};

-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    CGPoint point = [[touches anyObject] locationInView:self];
    CGFloat distance = DistanceBetweenTwoPoints(self.circleCenter, point);
    if(distance < self.radius){
        //inside the circle
    }
}

此代码假设您处理子类视图中的圆。

This code assumes, that you dealing with the circle inside a subclassed View.

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