如何检测特定区域的触摸 [英] How do I detect a touch over a specific area

问题描述

目前我看到触摸事件会向我显示触摸发生的UIView。但是，如果我需要检测一些非矩形形状的触摸，如圆形。我该如何做这样的事情？

Currently I see that a touch event will show me the UIView where the touch occured. But what if I need to detect a touch of some non rectangular shape, like a circle. How would I go about doing something like that ?

基本上我只想在用户触摸不可见的圆形区域内的某个地方时做某事。

Basically I want to do something only if the user touches somewhere within a circular area that's not visible.

感谢任何帮助/方向，TIA！

Any help/direction is appreciated, TIA!

推荐答案

你会这样做。请注意，'locationInView'将返回相对于指定视图的触摸坐标，因此无论视图在屏幕上的哪个位置，视图左上角的触摸都将返回（0,0）。

You would do it like so. Note that 'locationInView' will return the coordinates of the touch with respect to the specified view, so a touch in the top-left corner of a view will return (0,0) regardless of where that view is onscreen.

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event 
{   
  UITouch *touch = [touches anyObject];

  // gets the coordinats of the touch with respect to the specified view. 
  CGPoint touchPoint = [touch locationInView:self];

  // test the coordinates however you wish, 
  ...
}

要测试球体，您需要计算从触摸点到球体中心的距离，然后检查这是否小于球体半径。

To test against a sphere you would calculate the distance from the touch point to the center of the sphere, then check whether this was less than the sphere radius.

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