1.将接口返回的图片缓存到本地，由于写data到本地是耗时操作，为了不阻塞主线程，可开启子线程来做此操作
dispatch_queue_t queue = dispatch_queue_create("cn.xxx.queue", DISPATCH_QUEUE_SERIAL); // 异步存到沙盒 dispatch_async(queue, ^{ for (XWMainBtnSkinModel *skinM in self.models) { // btn_Bottom_4 NSString *path = [skinM.btnKey cacheDirWithSubpath:@"tabbar"]; // 下载图片 NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:skinM.img]]; [data writeToFile:path atomically:YES]; if([skinM.type isEqualToString:@"1"]){ // btn_Bottom_4_sel NSString *selImgKey = [NSString stringWithFormat:@"%@_sel",skinM.btnKey]; NSString *selpath = [selImgKey cacheDirWithSubpath:@"tabbar"]; // 下载图片 NSData *selImgData = [NSData dataWithContentsOfURL:[NSURL URLWithString:skinM.selImg]]; [selImgData writeToFile:selpath atomically:YES]; } } });
2.将请求到的图片，保存到内存，并给UI控件赋值，此处以tabbar为例
UIImage *img = [[UIImage alloc] init]; UIImage *selImg = [[UIImage alloc] init]; int i = 0; for (UITabBarItem *item in self.tabBar.items) { if(isNet){// 如果是从网络上获取，要告诉系统是@2x的图片 img = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:imgs[i]]] scale:2.0]; selImg = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:selImgs[i]]] scale:2.0]; }else{ img = [UIImage imageNamed:imgs[i]]; selImg = [UIImage imageNamed:selImgs[i]]; } item.image = [img imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal]; item.selectedImage = [selImg imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal]; i++; }
3.第二次打开app时，判断本地是否有缓存文件，如果有，就取之前缓存中的文件（这样用户体验更好，省去去网络上下载图片）
if (!isExist) { // 如果cache/tabbar这个目录不存在，就用默认主题 [self setUpChildController:mainPage title:@"首页" image:@"img_btn_mainpage_normal.png" selectedImage:@"img_btn_mainpage_select.png"]; [self setUpChildController:departClass title:@"分类" image:@"img_btn_class_normal" selectedImage:@"img_btn_class_select"]; [self setUpChildController:theme title:@"" image:@"img_btn_theme" selectedImage:@"img_btn_theme"]; [self setUpChildController:message title:@"消息" image:@"img_btn_message_normal" selectedImage:@"img_btn_message_select"]; [self setUpChildController:me title:@"我" image:@"img_btn_me_normal" selectedImage:@"img_btn_me_select"]; self.selectedIndex = 0; // 矫正TabBar图片位置，使之垂直居中显示 CGFloat offset = 3.0; for (UITabBarItem *item in self.tabBar.items) { item.imageInsets = UIEdgeInsetsMake(offset, 0, -offset, 0); if([item.title isEqualToString:@""]) { item.imageInsets = UIEdgeInsetsMake(7, 0, -7, 0); } } } else { //存在 [self setUpNetDataChildController:mainPage title:@"首页" image:@"btn_Bottom_1" selectedImage:@"btn_Bottom_1_sel"]; [self setUpNetDataChildController:departClass title:@"分类" image:@"btn_Bottom_2" selectedImage:@"btn_Bottom_2_sel"]; [self setUpNetDataChildController:theme title:@"" image:@"btn_Bottom_3" selectedImage:@"btn_Bottom_3_sel"]; [self setUpNetDataChildController:message title:@"消息" image:@"btn_Bottom_4" selectedImage:@"btn_Bottom_4_sel"]; [self setUpNetDataChildController:me title:@"我" image:@"btn_Bottom_5" selectedImage:@"btn_Bottom_5_sel"]; self.selectedIndex = 0; // 矫正TabBar图片位置，使之垂直居中显示 CGFloat offset = 3.0; for (UITabBarItem *item in self.tabBar.items) { item.imageInsets = UIEdgeInsetsMake(offset, 0, -offset, 0); if([item.title isEqualToString:@""]) { item.imageInsets = UIEdgeInsetsMake(7, 0, -7, 0); } } }
4.如果到了主题的过期时间，就应该切换回默认的主题：从接口中获取到主题到期时间，并设置定时器，当到期后，就删除本地缓存，并不在处理接口返回的图片数据。（直到接口中的到期时间重设，才处理接口中的图片）
[[NetRequest request]dataRequest:nil apiURL:__getSkinBtnImg needToCache:nil completeBlock:^(id result) { self.models = [XWMainBtnSkinModel mj_objectArrayWithKeyValuesArray:result[@"btnImg"]]; if(self.models.count > 0 ){ XWMainBtnSkinModel *model = self.models[0]; NSDateFormatter *date=[[NSDateFormatter alloc] init]; // endTime: "2016-04-16 16:45:59" [date setDateFormat:@"yyyy-MM-dd HH:mm:ss"]; /**服务返回的主题到期时间*/ NSDate *d=[date dateFromString:model.endTime]; NSTimeInterval late = [d timeIntervalSince1970]; NSDate *now = [NSDate date]; NSTimeInterval nowtiem = [now timeIntervalSince1970]; NSTimeInterval cha = late - nowtiem; /**到期时间和当前时间的差值*/ self.cha = cha; // 定时器（到期了就切回之前的默认主题） NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:cha target:self selector:@selector(returnSkan) userInfo:nil repeats:NO]; [[NSRunLoop mainRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];; if(self.cha <=0){ // 时间过了就不处理接口返回的数据了 return ; } if (!isExist) {//目录不存在(第一次从网络上直接获取图片) // 通知更改主题 [[NSNotificationCenter defaultCenter] postNotificationName:@"change" object:self userInfo:@{@"info":self.models}]; // 将图片 写入本地缓存起来，第二次就不用从网络上获取 [self writeFileToCache]; NSMutableArray *imgs = [NSMutableArray array]; NSMutableArray *selImgs = [NSMutableArray array]; for (XWMainBtnSkinModel *model in self.models) { if ([model.type isEqualToString:@"1"]) { [imgs addObject:model.img]; [selImgs addObject:model.selImg]; } } [self setUpTabbarWithImgs:imgs selImgs:selImgs isNet:YES]; [self.view setNeedsLayout]; } }else { // 如果没有请求到数据，就删除网络数据 [self returnSkan]; } } failedBlock:^(id error) { [SVProgressHUD showErrorWithStatus:error]; }];
// 到时间后，就换回之前的皮肤 - (void)returnSkan { if ([[NSFileManager defaultManager] fileExistsAtPath:self.fileCache]) { // 删除沙盒的数据 [[NSFileManager defaultManager] removeItemAtPath:self.fileCache error:NULL]; } // 该切回之前的主题了 [[NSNotificationCenter defaultCenter] postNotificationName:@"cha" object:self userInfo:nil]; NSMutableArray *normalImgs = [NSMutableArray arrayWithArray:@[@"img_btn_mainpage_normal.png",@"img_btn_class_normal",@"img_btn_theme",@"img_btn_message_normal",@"img_btn_me_normal"]]; NSMutableArray *selImgs = [NSMutableArray arrayWithArray:@[@"img_btn_mainpage_select.png",@"img_btn_class_select",@"img_btn_theme",@"img_btn_message_select",@"img_btn_me_select"]]; [self setUpTabbarWithImgs:normalImgs selImgs:selImgs isNet:NO]; }