UIImageView并不像UIButton那樣點擊鼠標就可以關聯點擊事件，也不像Android里有onClickListener，這個時候就需要借助UITapGestureRecognizer類，從類名上就可以看出，這個類就是用于處理tap(單擊)事件的。
創建兩個UIImageView對象,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:)]];

經測試，多個UIImageView不能共用一個UITapGestureRecognizer對象，之前調用的會沒效果。
根據點擊的view判斷來自誰的點擊

-(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");
}

}