关于IOS多个UIView添加点击

刚刚接触IOS开发，遇到以下问题想不通，希望高手给予指导。我给sendView、 payVIew、receiverView、 commentView设置点击事件，为什么

 UITapGestureRecognizer * singleRecognizer = [[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(viewClick:)];
 singleRecognizer.numberOfTapsRequired = 1;
 [self.sendView addGestureRecognizer:singleRecognizer]; 
 [self.payVIew addGestureRecognizer:singleRecognizer];
 [self.receiverView addGestureRecognizer:singleRecognizer];
 [self.commentView addGestureRecognizer:singleRecognizer];
 只有commentView能够响应点击事件，其他的三个UIView都无法响应点击事件，但是我要是改成

UITapGestureRecognizer * singleRecognizer = [[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(viewClick:)];
 singleRecognizer.numberOfTapsRequired = 1;
 [self.sendView addGestureRecognizer:singleRecognizer];
UITapGestureRecognizer * singleRecognizer1 = [[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(viewClick:)];
singleRecognizer1.numberOfTapsRequired = 1;
[self.payVIew addGestureRecognizer:singleRecognizer1];

UITapGestureRecognizer * singleRecognizer2 = [[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(viewClick:)];
singleRecognizer2.numberOfTapsRequired = 1;
[self.receiverView addGestureRecognizer:singleRecognizer2];

UITapGestureRecognizer * singleRecognizer3 = [[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(viewClick:)];
singleRecognizer3.numberOfTapsRequired = 1;
[self.commentView addGestureRecognizer:singleRecognizer3];