圓內的點

Question

給定圓的中心點和半徑，如何知道某個點（x，y）是否在圓內？任何人都知道嗎？謝謝。

Answer 1

最初你問過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 
    } 
} 

此代碼假定您處理子類查看中的圓。