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color
UIColor *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]];