iOS:图像和点击事件

问题：如何区分点的是哪张图片？

//
//  main.m
//  Hello
//
//  Created by lishujun on 14-8-28.
//  Copyright (c) 2014年 lishujun. All rights reserved.
//

#import <UIKit/UIKit.h>

// 视图控制器对象
@interface HelloWorldViewController : UIViewController
@end

@implementation HelloWorldViewController

-(void) loadView
{
    //创建视图对象
    UIView *contentView = [[UIView alloc]initWithFrame:[[UIScreen mainScreen] applicationFrame]];
    contentView.backgroundColor = [UIColor lightGrayColor];
    self.view = contentView;

    UIImageView *imageView =[[UIImageView alloc]initWithFrame:CGRectMake(, , , )];
    imageView.image = [UIImage imageNamed:@"100.png"];
    imageView.userInteractionEnabled = YES;
    UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(UesrClicked:)];
    [imageView addGestureRecognizer:singleTap];

    UIImageView *imageView2 =[[UIImageView alloc]initWithFrame:CGRectMake(, , , )];
    imageView2.image = [UIImage imageNamed:@"100.png"];
    imageView2.userInteractionEnabled = YES;
    UITapGestureRecognizer *singleTap2 = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(UesrClicked:)];
    [imageView2 addGestureRecognizer:singleTap2];

    [contentView addSubview:imageView];
    [contentView addSubview:imageView2];
}

-(void) UesrClicked:(id)sender
{
    //NSLog(@"%@", ((UIImageView*)((UITapGestureRecognizer *)sender).view).image);
    NSLog(@"%@",sender);
}

@end

// 委托对象
@interface HelloWorldAppDelegate : NSObject <UIApplicationDelegate>
{
    IBOutlet UIWindow *window;
}

@property (nonatomic, retain) UIWindow *window;
//必须声明为属性,声明为局部变量则无法绘制视图，显示为黑屏
@end

@implementation HelloWorldAppDelegate
@synthesize window;

-(void) applicationDidFinishLaunching:(UIApplication *)application
{
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen]bounds]];
    HelloWorldViewController *viewController = [[HelloWorldViewController alloc]init];
    self.window.rootViewController = viewController;
    [self.window makeKeyAndVisible];
}

@end

// 程序入口
int main(int argc, char * argv[])
{
    @autoreleasepool {
        return UIApplicationMain(argc, argv, nil, @"HelloWorldAppDelegate");
    }
}