解决方法
Apple在
Responder Chain中解释得非常好.您可以将以下功能添加到视图控制器：
override func touchesEnded(_ touches: Set<UITouch>,with event: UIEvent?) {
if let firstTouch = touches.first {
let hitView = self.view.hitTest(firstTouch.location(in: self.view),with: event)
if hitView === viewB {
print("touch is inside")
} else {
print("touch is outside")
}
}
}
