23&24day 网络、cell的代码块，以及常见错误

代码块

一、NSOperation

－cell的图片下载，防止图片重复下载

/** 存储下载图片的operation操作,保证一个URL对应一个操作*/@property (nonatomic,strong) NSMutableDictionary *operations; if (model.iconImage) {        [cell.imageView setImage:model.iconImage];    }else{        //下载图片        //获取operation        NSBlockOperation *operation = self.operations[model.icon];        //    HSWS(weakself);        if (operation == nil) {            //创建operation            operation = [NSBlockOperation blockOperationWithBlock:^{                //下载图片                NSURL *url = [NSURL URLWithString:model.icon];                UIImage *image = [UIImage imageWithData:[NSData dataWithContentsOfURL:url]];                [model setIconImage:image];                NSLog(@"%@",url);                //回到主线程进行cell的刷新                [[NSOperationQueue mainQueue]addOperationWithBlock:^{                    //显示cell                    [cell.imageView setImage:image];                }];            }];            //添加到队列--第一次创建operation才添加，保证一个URL对应的operation只执行一次            [self.queue addOperation:operation];            //添加到operations            self.operations[model.icon]= operation;        }    }

cell的图片下载-代码完善

- (UITableViewCell*)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{    //获取模型     HSAppsModel *model = self.dataList[indexPath.row];    NSString *indetifier = @"UITableViewCell";    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:indetifier];    if (nil == cell) {        cell = [[UITableViewCell alloc]initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:indetifier];    }    //设置cell    [cell.textLabel setText:model.name];    [cell.detailTextLabel setText:model.download];    if (self.images[model.icon]) {//已经存在图片        [cell.imageView setImage:self.images[model.icon]];    }else{        //说明未下载图片（未缓存过）        //设置占位图片        [cell.imageView setImage:[UIImage imageNamed:@"placeholder.jpg"]];//清除cell的图片－－cell重用 设置下载过程的默认图片        [self downloadWithUrl:model.icon indexPath:indexPath];    }    return cell;}#pragma mark - 下载图片- (void)downloadWithUrl:(NSString*)url indexPath:(NSIndexPath*)indexPath{    //获取operation    NSBlockOperation *operation = self.operations[url];    HSWS(weakself);    if (operation) {//正在下载中        return;    }    //创建operation    operation = [NSBlockOperation blockOperationWithBlock:^{        [NSThread sleepForTimeInterval:5];        NSURL *nsurl = [NSURL URLWithString:url];        //下载图片        UIImage *image = [UIImage imageWithData:[NSData dataWithContentsOfURL:nsurl]];        //缓存图片        if (image) {//字典不允许存放nil对象            weakself.images[url] = image;        }        //回到主线程进行cell的刷新        [[NSOperationQueue mainQueue]addOperationWithBlock:^{            //从字典中移除下载操作－－代表下载完成 保证一个URL对应的operation只执行一次            [weakself.operations removeObjectForKey:url];            //只要设置到正确的位置（row）,而直接操作cell－－因为cell会被重复利用            //                    [cell.imageView setImage:image];            //                    [tableView reloadData];            [weakself.tableView reloadRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationAutomatic];        }];    }];    //执行下载操作    [self.queue addOperation:operation];    //添加到operations－－防止重复下载    self.operations[url]= operation;}#pragma mark -scrollView Delegate- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView{    //暂停队列    [self.queue setSuspended:YES];}- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate{    //恢复队列    [self.queue setSuspended:NO];}/**内存处理*/- (void)didReceiveMemoryWarning{    [super didReceiveMemoryWarning];    [self.images removeAllObjects];    [self.operations removeAllObjects];    [self.queue cancelAllOperations];}

03.自定义operation

自动以operation的注意事项

cell的图片下载04-自定义Operation/** 自定义operation的注意点 1.如果是异步操作，无法访问主线程的自动释放池 2、经常检测操作是否被取消 */- (void)main{    @autoreleasepool {//创建自动释放池        if (self.isCancelled) {//检测操作是否被取消            return;        }        //下载图片        [NSThread sleepForTimeInterval:5];        NSURL *nsurl = [NSURL URLWithString:self.imageUrl];        UIImage *image = [UIImage imageWithData:[NSData dataWithContentsOfURL:nsurl]];        if (self.isCancelled) {            return;        }        //回到主线程        [[NSOperationQueue mainQueue] addOperationWithBlock:^{            //通知代理对象            if ([self.delegate respondsToSelector:@selector(downloadOperation:didFinishDownloadImage:)]) {                [self.delegate downloadOperation:self didFinishDownloadImage:image];            }        }];    }}

SDWebImage框架 的使用

 // 图片url    NSString *url = model.icon;////    [cell.imageView sd_setImageWithURL:[NSURL URLWithString:url] placeholderImage:model.placeholderImage completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, NSURL *imageURL) {////        NSLog(@"%@----------%d--------%@",image,cacheType,imageURL);//    }];///Users/devzkn/Library/Developer/CoreSimulator/Devices/5A6E02FF-A156-455B-AE43-C207F4E7FBC4/data/Containers/Data/Application/B1E84598-BCD5-4943-9859-853F3B0BCF9B/Library/Caches    [cell.imageView sd_setImageWithPreviousCachedImageWithURL:[NSURL URLWithString:url] andPlaceholderImage:model.placeholderImage options:SDWebImageProgressiveDownload | SDWebImageLowPriority progress:^(NSInteger receivedSize, NSInteger expectedSize) {        NSLog(@" 下载进度%f---%@",receivedSize*1.0/expectedSize,url);    } completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, NSURL *imageURL) {        NSLog(@"%@----------%d--------%@",image,cacheType,imageURL);    }];    //static const NSInteger kDefaultCacheMaxCacheAge = 60 * 60 * 24 * 7; // 1 week/**内存管理*/@implementation AppDelegate- (void) applicationDidReceiveMemoryWarning:(UIApplication *)application{    SDWebImageManager *imageMgr = [SDWebImageManager sharedManager];    [imageMgr cancelAll];    [imageMgr.imageCache clearMemory];}

NSURLConnection 的使用

1、异步请求

- (IBAction)login:(UIButton *)sender {    NSString *userName = self.userName.text;    if (userName.length ==0) {        //提示用户        [MBProgressHUD showError:@"请输入用户名"];        return;    }    NSString *pwd = self.pwd.text;    if (pwd.length == 0) {        //提示用户        [MBProgressHUD showError:@"请输入密码"];        return;    }    //创建get请求    //请求服务器--http://127.0.0.1:8080/MJServer/login?username=123&pwd=123&method=get&type=JSON    NSString *str = [[NSString stringWithFormat:@"http://127.0.0.1:8080/MJServer/login?username=%@&pwd=%@",userName,pwd] stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];    NSURL *url = [NSURL URLWithString:str];    NSURLRequest *request = [NSURLRequest requestWithURL:url];    NSLog(@"%s---start",__func__);    [NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse * _Nullable response, NSData * _Nullable data, NSError * _Nullable connectionError) {        NSLog(@"%@,%@",response,connectionError);        if (connectionError || data == nil) {            //发送请求失败            [MBProgressHUD showError:@"发送请求失败"];        }        //解析json        NSError *error ;        NSDictionary *answer = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:&error];        if (error) {            //解析失败            [MBProgressHUD showError:@"解析失败"];            return;        }        if (answer[@"success"]) {            [MBProgressHUD showSuccess:answer[@"success"]];        }else if (answer[@"error"]){            [MBProgressHUD showError:answer[@"error"]];        }    }];NSLog(@"%s----end",__func__);}

NSMutableURLRequest 的使用

设置请求体的数据类型

NSMutableURLRequest *request = [[NSMutableURLRequest alloc]initWithURL:HSUrl(@"order")];    [request setHTTPMethod:@"post"];    /*     发送JSON数据     订单数据：{  "shop_id" : "1239098",  "shop_name" : "lydia",  "user_id" : "kevin"}     */    NSDictionary *dict = @{@"shop_id":@"1239098",@"shop_name":@"lydia", @"user_id":@"kevin"};    [request setHTTPBody:[NSJSONSerialization dataWithJSONObject:dict options:NSJSONWritingPrettyPrinted error:nil ]];    [request setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];//see http://www.iana.org/assignments/media-types/

常见问题

颜色的定义方法colorWithRed G B

NSString *color = @"0x00b47f";upButton.backgroundColor = [self backColor:color];- (UIColor *)backColor:(NSString *)color{long colorLong = strtoul([color cStringUsingEncoding:NSUTF8StringEncoding], 0, 16);// 通过位与方法获取三色值int R = (colorLong & 0xFF0000 )>>16;int G = (colorLong & 0x00FF00 )>>8;int B = colorLong & 0x0000FF;//string转colorUIColor *wordColor = [UIColor colorWithRed:R/255.0 green:G/255.0 blue:B/255.0 alpha:1.0];return wordColor;}

URL的转码

#define HSUrl(path) [NSURL URLWithString:[[NSString stringWithFormat:@"%@%@",HSBaseUrl,path] stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]] //post 方式的时候    [request setHTTPBody:[[NSString stringWithFormat:@"username=%@&pwd=%@",userName,pwd] dataUsingEncoding:NSUTF8StringEncoding]];