ios - 延迟查看下一个 View Controller ，查看帖子中的详细信息？

Question

之后我有一个登录屏幕，它将移动到下一个 View Controller ，我已经使用了一些网络，如 http、json 从服务器获取数据。当我输入登录用户名/密码时，如果我单击登录按钮，它会延迟到 8 秒，之后只会移动到下一个 View Controller 。仍然我的登录屏幕单独显示 8 秒，然后只移动到下一个 View Controller 。

这是我的login controller.m:

@implementation mainViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    _username.delegate = self;
    _password.delegate = self;

    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    if (![defaults boolForKey:@"reg"]) {
        NSLog(@"no user reg");
        _logBtn.hidden = NO;
    }




}



- (void)viewWillAppear:(BOOL)animated
{
    [self.navigationController setNavigationBarHidden:YES animated:animated];
    [super viewWillAppear:animated];

    _username.text = nil;
    _password.text = nil;


}


 - (IBAction)LoginUser:(id)sender {



    if ([_username.text isEqualToString:@"sat"] && [_password.text isEqualToString:@"123"]) {
        NSLog(@"Login success");



        [self performSegueWithIdentifier:@"nextscreen" sender:self];


       }
    else {

        NSLog(@"login was unsucess");
        // Alert message


        UIAlertController *alertController = [UIAlertController alertControllerWithTitle:@"wrong"

                                                                                 message:@"Message"

                                                                          preferredStyle:UIAlertControllerStyleAlert];



        UIAlertAction *actionOk = [UIAlertAction actionWithTitle:@"Ok"

                                                           style:UIAlertActionStyleDefault

                                                         handler:nil];

        [alertController addAction:actionOk];

        [self presentViewController:alertController animated:YES completion:nil];


    }

}

这是我的 nextcontroller.m

 - (void)viewDidLoad {
        [super viewDidLoad];
//for search label data
        self.dataSourceForSearchResult = [NSArray new];
//collection of array to store value
         titleArray = [NSMutableArray array];


// here only i am getting data from server
        [self getdata];


        self.collectionView.dataSource = self;
        self.collectionView.delegate = self;
       [self.collectionView reloadData];


     }

帮帮我。如果我的问题不明白。我可以详细介绍我的帖子。在我的 nextcontroller.m [self getdata] 中，我正在从服务器 url 获取数据。谢谢

我的获取数据:

-(void)getdata {

    NSString *userName = @“users”;
    NSString *password = @“images”;
    NSData *plainData = [password dataUsingEncoding:NSUTF8StringEncoding];
    NSString *base64String = [plainData base64EncodedStringWithOptions:0];
    base64String=[self sha256HashFor: base64String];

    NSString *urlString = @"https://porterblog/image/file”;

    NSMutableURLRequest *request= [[NSMutableURLRequest alloc] init];
    [request setURL:[NSURL URLWithString:urlString]];
    [request setHTTPMethod:@"GET"];



    NSString *authStr = [NSString stringWithFormat:@"%@:%@", userName, base64String];
    NSData *authData = [authStr dataUsingEncoding:NSUTF8StringEncoding];



    NSString *authValue = [NSString stringWithFormat:@"Basic %@", [authData base64EncodedStringWithOptions:0]];

      [request setValue:authValue forHTTPHeaderField:@"Authorization"];





   NSData *returnData = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];


    NSString *str = [[NSString alloc] initWithData:returnData encoding:NSUTF8StringEncoding];


    NSError * error;

    self->arrayPDFName = [[NSMutableArray alloc]init];
    NSDictionary *jsonResults = [NSJSONSerialization JSONObjectWithData:returnData options:NSJSONReadingMutableContainers error:nil];



    NSDictionary *dictOriginal = jsonResults[@“birds”];
    [titleArray addObject:[NSString stringWithFormat:@" birds(%@)”, dictOriginal[@"count"]]];


    NSDictionary *dictOriginal2 = jsonResults[@"owl”];
    [titleArray addObject:[NSString stringWithFormat:@" Owl(%@)”, dictOriginal2[@"count"]]];



    NSDictionary *dictOriginal3 = jsonResults[@"pensq”];
    [titleArray addObject:[NSString stringWithFormat:@" Pensq(%@)”, dictOriginal3[@"count"]]];


    NSDictionary *dictOriginal4 = jsonResults[@“lion”];
    [titleArray addObject:[NSString stringWithFormat:@" lion(%@)”, dictOriginal4[@"count"]]];




    NSArray *arrayFiles = [NSArray arrayWithObjects: dictOriginal, dictOriginal2, dictOriginal3, dictOriginal4, nil];


     NSLog(@"str: %@", titleArray);


    for (NSDictionary *dict in arrayFiles) {
        NSMutableArray *arr = [NSMutableArray array];

        NSArray *a = dict[@"files"];
        for(int i=0; i < a.count; i ++) {


            NSString *strName = [NSString stringWithFormat:@"%@",[[dict[@"files"] objectAtIndex:i] valueForKey:@"name"]];

            [arr addObject:strName];
        }
        [arrayPDFName addObject:arr];
    }


    NSString *errorDesc;
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory1 = [paths objectAtIndex:0];
    NSString *plistPath = [documentsDirectory1 stringByAppendingPathComponent:@"SampleData.plist"];

    NSString *error1;

    returnData  = [ NSPropertyListSerialization dataWithPropertyList:jsonResults format:NSPropertyListXMLFormat_v1_0 options:0 error:&error];


    if(returnData ) {
        if ([returnData  writeToFile:plistPath atomically:YES]) {
            NSLog(@"Data successfully saved.");
        }else {
            NSLog(@"Did not managed to save NSData.");
        }
    }
    else {
        NSLog(@"%@",errorDesc);
    }


    NSDictionary *stringsDictionary = [NSDictionary dictionaryWithContentsOfFile:plistPath];



}

已编辑:

`- (void)viewDidLoad {

    [super viewDidLoad];

  dispatch_async(dispatch_get_global_queue( DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^(void){



        self.dataSourceForSearchResult = [NSArray new];

        titleArray = [NSMutableArray array];



        //Background Tasks

        [self getdata];

        dispatch_async(dispatch_get_main_queue(), ^(void){

            //Run UI Updates

 self.collectionView.dataSource = self;

                self.collectionView.delegate = self;

               [self.collectionView reloadData];

         self.navigationItem.hidesBackButton = YES;

  });

    });

 }`

Answer 1

您正在使用主线程获取数据，您需要在后台执行此操作，然后调用您需要的代码(我看到的是重新加载 collectionView)我假设是因为您没有显示 getdata 方法代码如果是这种情况，您可以使用此代码:

dispatch_async(dispatch_get_global_queue( DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^(void){
    //Background Tasks
    [self getdata];
    dispatch_async(dispatch_get_main_queue(), ^(void){
        //Run UI Updates
        [self.collectionView reloadData];
    });
});

这意味着您的 VC 将立即显示，但 collectionView 在您完成加载数据后填充，您可以在加载时放置一些旧数据，如 Facebook 应用程序(您会看到最新检索的帖子，直到完成加载)。

编辑:在您的代码中，您将 nextController 中的 viewdidload 方法替换为下一个代码:

- (void)viewDidLoad {
  [super viewDidLoad];
  //for search label data
  self.dataSourceForSearchResult = [NSArray new];
  //collection of array to store value
  titleArray = [NSMutableArray array];
        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^(void){
    //Background Tasks
    [self getdata];
    dispatch_async(dispatch_get_main_queue(), ^(void){
        //Run UI Updates
        [self.collectionView reloadData];
    });
    });

self.collectionView.dataSource = self;
self.collectionView.delegate = self;

}