iOS —— 天气预报仿写总结

在iOS中，最常见的网络请求方式是NSURLSession，它是苹果推荐的现代API，简单安全且易于拓展。

一次完整的网络请求流程：

1. 构造 NSURL 对象

2. 创建 NSURLSessionDataTask

3. 发起请求（resume）

4. 在回调中解析数据

5. 回到主线程更新 UI

下面，我们用一个简单的程序来试一下。

NSString *city = @"Beijing";
NSString *apiKey = @"你的API密钥";
NSString *urlString = [NSString stringWithFormat:@"https://api.weatherapi.com/v1/current.json?key=%@&q=%@&lang=zh", apiKey, city];
urlString = [urlString stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet URLQueryAllowedCharacterSet]];

NSURL *url = [NSURL URLWithString:urlString];
NSURLSessionDataTask *task = [[NSURLSession sharedSession] dataTaskWithURL:url completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
    if (error) {
        NSLog(@"请求失败：%@", error.localizedDescription);
        return;
    }

    NSDictionary *json = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
    NSLog(@"天气数据：%@", json);
    
    dispatch_async(dispatch_get_main_queue(), ^{
        // 更新 UI
    });
}];
[task resume];

首页

    [[NSNotificationCenter defaultCenter] addObserver:self
                                                 selector:@selector(handleAddCityNotification:)
                                                     name:@"AddNewCityNotification"
                                                   object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self
                                                    selector:@selector(handleDeleteCityNotification:)
                                                        name:@"DeleteCityNotification"
                                                      object:nil];

接收两个通知，一个是搜索页面的城市，另一个是详情页面的删除指令。

-(void) handleAddCityNotification:(NSNotification *)notification {
    NSDictionary *userInfo = [notification userInfo];
    NSString *newCity = userInfo[@"cityName"];

    BOOL exists = NO;
    for (NSDictionary *city in self.cityData) {
        if ([city[@"name"] isEqualToString:newCity]) {
            exists = YES;
            break;
        }
    }
    if (!exists) {
        [self.cityData addObject:@{@"name": newCity}];
        [self createUrl];
    }
}


- (void)handleDeleteCityNotification:(NSNotification *)notification {
    NSDictionary *userInfo = [notification userInfo];
    NSString *cityName = userInfo[@"cityName"];
    
    // 从城市列表中删除该城市
    NSMutableArray *citiesToRemove = [NSMutableArray array];
    for (NSDictionary *city in self.cityData) {
        if ([city[@"name"] isEqualToString:cityName]) {
            [citiesToRemove addObject:city];
        }
    }
    [self.cityData removeObjectsInArray:citiesToRemove];
    [self.tableView reloadData];
}

这个页面要执行两个操作： 点击加号添加城市，删除城市。

这里给出我的网络请求代码： 

- (void)createUrl {
    if (self.cityData.count == 0) return;
    
    dispatch_group_t group = dispatch_group_create();
    NSURLSession *session = [NSURLSession sharedSession];
    NSMutableArray *tempDicArray = [NSMutableArray array];
    NSLog(@"1");
    for (NSDictionary *city in self.cityData) {
        dispatch_group_enter(group);
        
        NSString *cityName = city[@"name"];
        NSString *urlString = [NSString stringWithFormat:@"https://api.weatherapi.com/v1/current.json?key=2db0265c1d084416b9275428252207&q=%@&lang=zh   ", cityName];
        urlString = [urlString stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet URLQueryAllowedCharacterSet]];
        NSURL *url = [NSURL URLWithString:urlString];
        
        NSURLSessionDataTask *task = [session dataTaskWithURL:url completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
            if (error) {
                NSLog(@"错错错！！ %@: %@", city, error.localizedDescription);
                dispatch_group_leave(group);
                return;
            }
            if (data) {
                    NSError *jsonError;
                    //解析数据
                    NSDictionary *dic = [NSJSONSerialization JSONObjectWithData:data options:0 error:&jsonError];
                    if (jsonError) {
                        NSLog(@"JSON解析失败: %@", jsonError.localizedDescription);
                    } else {
                        NSLog(@"API响应: %@", dic);
                                
                    // 检查是否有错误
                    if (dic[@"error"]) {
                    NSLog(@"API返回错误: %@", dic[@"error"][@"message"]);
                    } else {
                        @synchronized (tempDicArray) {
                            //赋值到tempDicArray
                        [tempDicArray addObject:dic];
                        NSLog(@"成功添加城市: %@", cityName);
                        }
                    }
                }
        } else {
            NSLog(@"无响应数据");
        }
            dispatch_group_leave(group);
            }];
                [task resume];
}
                
    dispatch_group_notify(group, dispatch_get_main_queue(), ^{
    NSLog(@"所有请求完成，获取到%ld个城市数据", tempDicArray.count);
        //最终到dicArray
    self.dicArray = tempDicArray;
    [self.tableView reloadData];
    });
}

// 添加支持滑动删除
- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath {
    return YES;
}

搜索页面

-(void) addCityToMain:(NSDictionary *)cityInfo {
    NSString *cityName = cityInfo[@"name"];
    NSDictionary *userInfo = @{@"cityName": cityName};
    [[NSNotificationCenter defaultCenter] postNotificationName:@"AddNewCityNotification" object:nil userInfo:userInfo];
    
    // 关闭添加页面
//    [self dismissViewControllerAnimated:YES completion:nil];
}

//选中哪个就传给主页
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    [tableView deselectRowAtIndexPath:indexPath animated:YES];
    
    if (indexPath.row < self.searchResults.count) {
        NSDictionary *city = self.searchResults[indexPath.row];
        
        DetailViewController *detailVC = [[DetailViewController alloc] init];
        detailVC.cityName = city[@"name"];
        detailVC.canAddCity = YES;
        
        UINavigationController *nav = [[UINavigationController alloc] initWithRootViewController:detailVC];
        nav.modalPresentationStyle = UIModalPresentationFullScreen;
        [self presentViewController:nav animated:YES completion:nil];
    }
}

当我们点击其中一行时，我们会跳转到该城市

城市详细天气

给出我的每小时天气预报代码

- (void)setupHourlyForecastData {
    NSArray *forecastDays = self.weatherData[@"forecast"][@"forecastday"];
    if (forecastDays.count == 0) return;
    
    //WeatherAPI 返回的 forecast 结构中，每天包含一个 hour 数组（24 小时）。为了支持“跨天展示”，你先拼接所有天的小时数组
    // 拼接所有 forecastday 的 hour 数据
    NSMutableArray *allHours = [NSMutableArray array];
    for (NSDictionary *day in forecastDays) {
        NSArray *hours = day[@"hour"];
        if (hours) [allHours addObjectsFromArray:hours];
    }
    if (allHours.count == 0) return;
    
    UIView *hourlyCard = [self.contentView viewWithTag:1000];
    UIScrollView *scrollView = [hourlyCard viewWithTag:1001];
    if (!scrollView) return;
    
    CGFloat itemWidth = 60;
    CGFloat spacing = 10;

    //当前小时
    NSDate *now = [NSDate date];
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    formatter.dateFormat = @"yyyy-MM-dd HH";
    NSString *nowHourString = [formatter stringFromDate:now];
    NSInteger startIndex = 0;
    //找出当前时间匹配的小时
    for (int i = 0; i < allHours.count; i++) {
        NSString *hourString = [allHours[i][@"time"] substringToIndex:13];
        if ([hourString isEqualToString:nowHourString]) {
            startIndex = i;
            break;
        }
    }

    //主要是防止数组越界
    NSInteger count = MIN(24, allHours.count - startIndex);
    //给7个格子赋值
    for (int i = 0; i < count; i++) {
        NSDictionary *hour = allHours[startIndex + i];
        NSString *time = [hour[@"time"] substringFromIndex:11];
        NSString *temp = [NSString stringWithFormat:@"%.0f°", [hour[@"temp_c"] floatValue]];
        NSString *iconUrl = [NSString stringWithFormat:@"https:%@", hour[@"condition"][@"icon"]];

        UIView *hourView = [[UIView alloc] initWithFrame:CGRectMake(i * (itemWidth + spacing), 0, itemWidth, 70)];

        UILabel *timeLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, itemWidth, 20)];
        timeLabel.text = time;
        timeLabel.font = [UIFont systemFontOfSize:12];
        timeLabel.textColor = [UIColor whiteColor];
        timeLabel.textAlignment = NSTextAlignmentCenter;
        [hourView addSubview:timeLabel];

        UIImageView *icon = [[UIImageView alloc] initWithFrame:CGRectMake(10, 20, 40, 30)];
        icon.contentMode = UIViewContentModeScaleAspectFit;
        [hourView addSubview:icon];
        [self loadIcon:iconUrl forImageView:icon];

        UILabel *tempLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 50, itemWidth, 20)];
        tempLabel.text = temp;
        tempLabel.font = [UIFont systemFontOfSize:12];
        tempLabel.textColor = [UIColor whiteColor];
        tempLabel.textAlignment = NSTextAlignmentCenter;
        [hourView addSubview:tempLabel];

        [scrollView addSubview:hourView];
    }

    scrollView.contentSize = CGSizeMake((itemWidth + spacing) * count, 70);
}//每小时天气

同时，我下面的每部分都以卡片形式呈现

//卡片
- (UIView *)createCardViewWithFrame:(CGRect)frame {
    UIView *card = [[UIView alloc] initWithFrame:frame];
    card.backgroundColor = [UIColor colorWithWhite:1 alpha:0.2];
    card.layer.cornerRadius = 20;
    card.layer.borderWidth = 1;
    card.layer.borderColor = [UIColor colorWithWhite:1 alpha:0.3].CGColor;
    return card;
}
//卡片标题
- (UILabel *)createSectionTitleLabel:(NSString *)title frame:(CGRect)frame {
    UILabel *label = [[UILabel alloc] initWithFrame:frame];
    label.text = title;
    label.font = [UIFont systemFontOfSize:20 weight:UIFontWeightBold];
    label.textColor = [UIColor whiteColor];
    return label;
}

我的背景可以根据天气不同自动切换，代码如下：

- (void)setBackgroundBasedOnWeather {
    if (!self.weatherData) return;
    
    NSDictionary *current = self.weatherData[@"current"];
    NSDictionary *condition = current[@"condition"];
    NSInteger code = [condition[@"code"] integerValue];

    NSString *bgImageName;

    // 晴天
    if (code == 1000) {
        bgImageName = @"pic1.jpg";
    }
    // 多云或阴天
    else if (code >= 1003 && code <= 1009) {
        bgImageName = @"pic2.jpg";
    }
    // 雨（小雨~大雨）
    else if ((code >= 1063 && code <= 1087) || (code >= 1150 && code <= 1195) || (code >= 1240 && code <= 1246)) {
        bgImageName = @"pic3.jpg";
    }
    // 雪（小雪~暴雪）
    else if ((code >= 1066 && code <= 1074) || (code >= 1114 && code <= 1237)) {
        bgImageName = @"pic4.jpg";
    }
    // 雷暴、雨夹雪等恶劣天气
    else if (code >= 1273 && code <= 1282) {
        bgImageName = @"pic5.jpg";
    }
    // 默认
    else {
        bgImageName = @"pic1.jpg";
    }

    self.backgroundImageView.image = [UIImage imageNamed:bgImageName];
}

//日期字符串转换为周几
- (NSString *)formatDate:(NSString *)dateString {
    NSDateFormatter *inputFormatter = [[NSDateFormatter alloc] init];
    inputFormatter.dateFormat = @"yyyy-MM-dd";
    NSDate *date = [inputFormatter dateFromString:dateString];
    
    NSDateFormatter *outputFormatter = [[NSDateFormatter alloc] init];
    outputFormatter.locale = [NSLocale localeWithLocaleIdentifier:@"zh_CN"];
    outputFormatter.dateFormat = @"EEE";
    return [outputFormatter stringFromDate:date];
}

详情页的删除按钮：

- (void)deleteCity {
    if (self.cityName) {
        NSDictionary *userInfo = @{@"cityName": self.cityName};
        [[NSNotificationCenter defaultCenter] postNotificationName:@"DeleteCityNotification"
                                                            object:nil
                                                          userInfo:userInfo];
        [self dismissViewControllerAnimated:YES completion:nil];
    }
}

关于多个城市横向滑动查看详情，我使用了UIPageController。

- (id)init {
    self = [super initWithTransitionStyle:UIPageViewControllerTransitionStyleScroll
                     navigationOrientation:UIPageViewControllerNavigationOrientationHorizontal
                                   options:nil];
    return self;
}

这段代码实现了页面的横向滑动效果。

// MainVC.m


- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    [tableView deselectRowAtIndexPath:indexPath animated:YES];
    
    NSMutableArray *cityNames = [NSMutableArray array];
    for (NSDictionary *city in self.cityData) {
        [cityNames addObject:city[@"name"]];
    }
    CitiesDetailViewController *containerVC = [[CitiesDetailViewController alloc] init];
    containerVC.cityNames = cityNames;
    containerVC.initialIndex = indexPath.section;
    containerVC.modalPresentationStyle = UIModalPresentationFullScreen;
    [self presentViewController:containerVC animated:YES completion:nil];
}

// CitiesDetailViewController.m

- (void)viewDidLoad {
    [super viewDidLoad];
    
    self.delegate = self;
    self.dataSource = self;

    self.cities = self.cityNames;           // 城市名列表由外部传入
    self.currentIndex = self.initialIndex;  // 初始城市索引也由外部设置

    DetailViewController *initialVC = [self detailViewControllerForIndex:self.initialIndex];
    [self setViewControllers:@[initialVC] direction:UIPageViewControllerNavigationDirectionForward animated:NO completion:nil];

#pragma mark - Page View Controller Data Source
// 获取前一个VC
- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(UIViewController *)viewController {
    //下标
    NSInteger index = [(DetailViewController *)viewController index];
    //不是第一个就去上一个
    if (index > 0) {
        return [self detailViewControllerForIndex:index - 1];
    }
    return nil;
}

//获取后一个VC
- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController {
    NSInteger index = [(DetailViewController *)viewController index];
    if (index < self.cities.count - 1) {
        return [self detailViewControllerForIndex:index + 1];
    }
    return nil;
}

//进入指定页面
- (DetailViewController *)detailViewControllerForIndex:(NSInteger)index {
    if (index < 0 || index >= self.cities.count) return nil;
    
    DetailViewController *detailVC = [[DetailViewController alloc] init];
    detailVC.cityName = self.cities[index];
    detailVC.index = index;
    detailVC.canAddCity = NO;
    
    return detailVC;
}

- (void)deleteCurrentCity {
    if (self.cities.count == 0) {
        [self dismissViewControllerAnimated:YES completion:nil];
        return;
    }

    // 获取当前显示的视图控制器
    DetailViewController *currentVC = (DetailViewController *)self.viewControllers.firstObject;
    NSInteger currentIndex = currentVC.index;
    
    // 防止索引越界
    if (currentIndex >= self.cities.count) {
        [self dismissViewControllerAnimated:YES completion:nil];
        return;
    }

    NSString *cityName = self.cities[currentIndex];

    // 发送删除通知
    NSDictionary *userInfo = @{@"cityName": cityName};
    [[NSNotificationCenter defaultCenter] postNotificationName:@"DeleteCityNotification"
                                                        object:nil
                                                      userInfo:userInfo];

    // 从数据源中删除
    NSMutableArray *mutableCities = [self.cities mutableCopy];
    [mutableCities removeObjectAtIndex:currentIndex];
    self.cities = [mutableCities copy];

    // 如果删除后没有城市了，关闭页面
    if (self.cities.count == 0) {
        [self dismissViewControllerAnimated:YES completion:nil];
        return;
    }

    // 计算新的当前索引
    NSInteger newIndex;
    if (currentIndex >= self.cities.count) {
        newIndex = self.cities.count - 1;
    } else {
        newIndex = currentIndex;
    }
    
    // 确定导航方向：如果删除的是最后一个，则向前翻一页，否则保持当前页
    UIPageViewControllerNavigationDirection direction = UIPageViewControllerNavigationDirectionForward;
    if (newIndex < currentIndex) {
        direction = UIPageViewControllerNavigationDirectionReverse;
    }

    // 获取新的视图控制器
    DetailViewController *newVC = [self detailViewControllerForIndex:newIndex];
    if (newVC) {
        [self setViewControllers:@[newVC]
                       direction:direction
                        animated:YES
                      completion:nil];
        self.currentIndex = newIndex;
    }
}