[問題] 有關使用NSURLSession抓Json資料的問題

看板MacDev作者strife00 (strifecloud)時間9年前 (2016/04/16 19:16)推噓3(3推 0噓 20→)

留言23則, 6人參與討論串1/2 (看更多)

大家好，小弟最近想自己試著使用NSURLSession來寫寫看如何抓到JSON的資料主要架構就是用一個TableViewControler把抓回來的JSON資料一筆一筆顯示出來上網查了許多資料自己試做後，有成功抓到JSON資料，但是目前遇到問題是資料回來之前， TableViewController 就已經建立好了，所以一開APP不會顯示資料，我需要等資料回來後，準備一個執行[TableView reloadData]的方法的按鈕，按下後才能在TableView上顯示資料。我參照網路上以及Apple的一些官方sample，把抓資料的NSURLSession寫在AppDelegate的Class裡可能應為對於能在哪個時機點讓APP自動執行reloadData還不是很了解，想請教各位大大，感恩！程式碼如下（目前的寫法曾經有幾次成功在APP執行後自動顯示，但成功機率很低..）： static NSString * const taipeiUrl = @"http://data.taipei.gov.tw/opendata/apply/json/RkRDNjk0QzUtNzdGRC00ODFCLUJBNDktNEJCMUVCMDc3ODFE"; @interface AppDelegate () @end @implementation AppDelegate - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { NSURLSession *session = [NSURLSession sharedSession]; NSURLSessionDataTask *dataTask = [session dataTaskWithURL:[NSURL URLWithString:taipeiUrl] completionHandler:^(NSData *data, NSURLResponse *response, NSError *error){ NSLog(@"error = %@", [error description]); if (error != nil) { [[NSOperationQueue mainQueue] addOperationWithBlock: ^{ [UIApplication sharedApplication].networkActivityIndicatorVisible = NO; if ([error code] == NSURLErrorAppTransportSecurityRequiresSecureConnection) { abort(); } else { [self handleError:error]; } }]; } else{ NSDictionary *json = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:nil]; self.newsArray = [json valueForKey:@"name"]; NSLog(@"%@", self.newsArray); __weak AppDelegate *weakSelf = self; dispatch_async(dispatch_get_main_queue(), ^(void){ NewsTableViewController *rootViewController = (NewsTableViewController *)[(UINavigationController *)weakSelf.window.rootViewController topViewController]; [rootViewController.tableView reloadData]; }); // show in the status bar that network activity is starting [UIApplication sharedApplication].networkActivityIndicatorVisible = NO; } }]; [dataTask resume]; //UI self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]]; //create the navigation controller and add the controllers view to the window self.navigationController = [[UINavigationController alloc] init]; [self.window addSubview:[self.navigationController view]]; NewsTableViewController *newsViewController = [[NewsTableViewController alloc] initWithNibName:@"NewsTableViewController" bundle:nil]; //push the first viewcontroller into the navigation view controller stack [self.navigationController pushViewController:newsViewController animated:YES]; self.window.backgroundColor = [UIColor whiteColor]; self.window.rootViewController = self.navigationController; [self.window makeKeyAndVisible]; // show in the status bar that network activity is starting [UIApplication sharedApplication].networkActivityIndicatorVisible = YES; return YES; } // handleError:error // Reports any error with an alert which was received from connection or loading failures. - (void)handleError:(NSError *)error { NSString *errorMessage = [error localizedDescription]; // alert user that our current record was deleted, and then we leave this view controller // UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"Cannot Show Top Paid Apps" message:errorMessage preferredStyle:UIAlertControllerStyleActionSheet]; UIAlertAction *OKAction = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:^(UIAlertAction *action) { // dissmissal of alert completed }]; [alert addAction:OKAction]; [self.window.rootViewController presentViewController:alert animated:YES completion:nil]; } -- ※ 發信站: 批踢踢實業坊(ptt.cc), 來自: 123.193.12.200 ※ 文章網址: https://www.ptt.cc/bbs/MacDev/M.1460805376.A.988.html

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