UIImageView并不像UIButton那样点击鼠标就可以关联点击事件，也不像Android里有onClickListener，这个时候就需要借助UITapGestureRecognizer类，从类名上就可以看出，这个类就是用于处理tap(单击)事件的。
创建两个UIImageView对象,imageView1和imageView2

[imageView1 setUserInteractionEnabled:YES];

[imageView2 setUserInteractionEnabled:YES];

[imageView1 addGestureRecognizer:[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(clickCategory:)]];

[imageView2 addGestureRecognizer:[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(clickCategory:)]];

经测试，多个UIImageView不能共用一个UITapGestureRecognizer对象，之前调用的会没效果。
根据点击的view判断来自谁的点击

-(void)clickCategory:(UITapGestureRecognizer *)gestureRecognizer
{
NSLog(@"click");
NSLog(@"%hhd",[gestureRecognizer isMemberOfClass:[UITapGestureRecognizer class]]);

UIView *viewClicked=[gestureRecognizer view];
if (viewClicked==imageView1) {
    NSLog(@"imageView1");
}else if(viewClicked==imageView2)
{
    NSLog(@"imageView2");
}

}