UI阶段的 Target/Action设计模式

问题:我怎么实现通过点击,一个UIImageView的对象,实现相应的操作,这里以更换图片为例

思路一:仿照UIButton的target/action设计模式
(MFC 手动管理内存)

创建一个类继承UIImageView,来实现该功能
ButtonImageView.h

#import <UIKit/UIKit.h>@interface ButtonImageView : UIImageView@property(nonatomic,strong)id target;@property(nonatomic,assign)SEL action;- (instancetype)initWithFrame:(CGRect)frame target:(id)target action:(SEL)action;@end

ButtonImageView.m

#import "ButtonImageView.h"@implementation ButtonImageView- (instancetype)initWithFrame:(CGRect)frame target:(id)target action:(SEL)action{    //  完整的初始化方法    self = [super initWithFrame:frame];    if (self) {        self.target = target;        self.action = action;    }    return self;}//  由于你需要点击,之后有相关的操作//  重写touches的相关方法- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{}- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event{}- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event{    //  更换图片,只需要点击一下    //  这里需要用该类的一个对象,去调用该类的方法    [self.target performSelector:self.action withObject:self];}- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{}

创建一个根试图控制器:创建一个根视图控制器对象,赋值给window的跟视图属性

#import “AppDelegate.m”

#import "AppDelegate.h"#import "RootViewController.h"@interface AppDelegate ()@end@implementation AppDelegate- (void)dealloc{    [_window release];    [super dealloc];}- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {    self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]]autorelease    ];    // Override point for customization after application launch.    self.window.backgroundColor = [UIColor whiteColor];    [self.window makeKeyAndVisible];    // 设置根视图控制器    RootViewController *rootVC = [[RootViewController alloc]init];    self.window.rootViewController = rootVC;    [rootVC release];    return YES;}@end

RootViewController.m

#import "RootViewController.h"#import "ButtonImageView.h"@interface RootViewController ()@end@implementation RootViewController- (void)viewDidLoad {    [super viewDidLoad];    // Do any additional setup after loading the view.    UIImage *img = [UIImage imageNamed:@"5.jpg"];    ButtonImageView *BtnImgView = [[ButtonImageView alloc]initWithFrame:[UIScreen mainScreen].bounds                                      target:self action:@selector(BtnImgViewClick:)];       BtnImgView.image = img;    BtnImgView.userInteractionEnabled = YES;       [self.view addSubview:BtnImgView];       [BtnImgView release];}- (void)BtnImgViewClick:(ButtonImageView *)btnImgView{    //  更换图片    UIImage *img1 = [UIImage imageNamed:@"6.jpeg"];    btnImgView.image = img1;}- (void)didReceiveMemoryWarning {    [super didReceiveMemoryWarning];    // Dispose of any resources that can be recreated.}

**小结:
这个模式设计出来的类的对象,就像一个button一样,当你点击该对象后,将返回该类的touchesEnd方法,将你初始化出来的一个对象的target调用该对象的action方法,其实还可以携带参数(withObject:…).参数需不需要,根据你的action方法决定.这样做就是为了降低类和类之间的耦合,从而实现封装和提高代码的复用性功能.**