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前言

• 这周写天气预报时需要网络请求才开始正式接触，理解的可能不够全面，有什么不对的地方，敬请斧正

• 这篇以搜索城市时的联想为例，即

  

思路

• 第一步当然是初始化UITextField和UITableView，联想词在UITableView里显示
• 然后创建URL及协议方法
• 因为输入一个字符联想词也需要同时改变，故我在UITextField的协议方法 - (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string； 里使用了创建URL方法
• 最后解析数据

创建网络请求的五大步骤

• 创建请求地址
• 创建请求类
• 创建会话
• 根据会话创建任务
• 启动任务

一些会使用到的方法解释

- stringByAddingPercentEncodingWithAllowedCharacters:

- sessionWithConfiguration: delegate: delegateQueue:

-(void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveResponse:(NSURLResponse *)response completionHandler:(void (^)(NSURLSessionResponseDisposition))completionHandler

-(void)URLSession:(NSURLSession *)session dataTask:( NSURLSessionDataTask *)dataTask didReceiveData:( NSData *)data

-(void)URLSession:(NSURLSession *)session task:( NSURLSessionTask *)task didCompleteWithError:( NSError *)error

- [[NSOperationQueue mainQueue] addOperationWithBlock:

代码

首先在 ViewController.h 里声明一些属性及协议

@interface ViewController : UIViewController
   
    @property (nonatomic, strong) UITextField *textField;@property (nonatomic, strong) UITableView *tableView;@property (nonatomic, strong) NSMutableData *data;@property (nonatomic, strong) NSMutableArray *cityArray;
   

在 ViewController.m 里初始化UITextField和UITableView

- (void)viewDidLoad {
       [super viewDidLoad];    // Do any additional setup after loading the view.        _textField = [[UITextField alloc] init];    _textField.delegate = self;    _textField.frame = CGRectMake(50, 100, [UIScreen mainScreen].bounds.size.width - 100, 50);    [self.view addSubview:_textField];    _textField.borderStyle = UITextBorderStyleRoundedRect;    _textField.keyboardType = UIKeyboardTypeDefault;    [self creatTableView];    }- (void)creatTableView {
           _tableView = [[UITableView alloc] initWithFrame:CGRectMake(50, 150, [UIScreen mainScreen].bounds.size.width - 100, 500) style:UITableViewStylePlain];    [self.view addSubview:_tableView];    _tableView.delegate = self;    _tableView.dataSource = self;    [_tableView registerClass:[UITableViewCell class] forCellReuseIdentifier:@"111"];    UIView *view = [[UIView alloc] init];    _tableView.tableFooterView = view;    }

然后创建URL及协议方法

- (void)creatUrl {
       //1.创建请求地址    NSString *urlString = [NSString stringWithFormat:@"https://search.heweather.com/find?location=%@&key=71f533964a994355bb1abfccb161d241", _textField.text];    //处理字符    urlString = [urlString stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet URLQueryAllowedCharacterSet]];    //创建URL    NSURL *url = [NSURL URLWithString:urlString];    NSLog(@"%@", urlString);    //2.创建请求类    NSURLRequest *request = [NSURLRequest requestWithURL:url];    //3.创建会话    //delegateQueue 表示协议方法在哪个线程中执行    NSURLSession *session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration] delegate:self  delegateQueue:[NSOperationQueue mainQueue]];    //4.根据会话创建任务    NSURLSessionDataTask *dataTask = [session dataTaskWithRequest:request];    //5.启动任务    [dataTask resume];    }

URL协议方法：

//接收服务器的响应-(void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveResponse:(NSURLResponse *)response completionHandler:(void (^)(NSURLSessionResponseDisposition))completionHandler {
       NSLog(@"didReceiveResponse");        if(self.data == nil){
           self.data = [[NSMutableData alloc] init];    } else {
           self.data.length = 0;    }    //允许接收数据    completionHandler(NSURLSessionResponseAllow);}//接收到数据，该方法会被调用多次- (void)URLSession:(NSURLSession *)session dataTask:( NSURLSessionDataTask *)dataTask didReceiveData:( NSData *)data {
       NSLog(@"didReceiveData");        [self.data appendData:data];}//数据请求完成或者请求出现错误调用的方法- (void)URLSession:(NSURLSession *)session task:( NSURLSessionTask *)task didCompleteWithError:( NSError *)error {
       NSLog(@"didCompleteWithError");    if (error == nil) {
           //解析数据        NSDictionary *secondDictionary = [NSJSONSerialization JSONObjectWithData:_data options:kNilOptions error:nil];        NSMutableArray *timeArray = [[NSMutableArray alloc] init];        timeArray = secondDictionary[@"HeWeather6"][0][@"basic"];        for (int i = 0; i < timeArray.count; i++) {
               NSMutableString *str = [NSMutableString stringWithFormat:@"%@-%@",timeArray[i][@"parent_city"],timeArray[i][@"location"]];            [_cityArray addObject: str];        }        for (int i = 0; i < _cityArray.count; i++) {
               NSLog(@"%@", _cityArray[i]);        }        NSLog(@"-----------over");    } else {
           NSLog(@"error = %@", error);    }    [[NSOperationQueue mainQueue] addOperationWithBlock:^{
           [self->_tableView reloadData];    }];    }

UITableView的协议方法：

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
           UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"111" forIndexPath:indexPath];    while ([cell.contentView.subviews lastObject] != nil) {
           [(UIView *)[cell.contentView.subviews lastObject] removeFromSuperview];    }    cell.textLabel.text = _cityArray[indexPath.row];    cell.textLabel.font = [UIFont systemFontOfSize:20];    cell.textLabel.textAlignment = NSTextAlignmentCenter;        return cell;    }- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
       return _cityArray.count;}- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
       return 30;}- (void)touchesBegan:(NSSet
   
     *)touches withEvent:(UIEvent *)event {
       [_textField endEditing:YES];}
   

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