ios - 如何初始化另一个 View Controller 的值

Question

在我的应用程序中，当用户从浏览器重定向到应用程序时，我会显示注册页面。因为我想从 url 变量中插入值。所以首先我从 url 获取值，然后显示带有文本框值的页面。但它没有设置文本框值。

我的代码:

    - (BOOL)application:(UIApplication *)application openURL:(NSURL *)url sourceApplication:(NSString *)sourceApplication annotation:(id)annotation {
    NSString *urlString=[NSString stringWithContentsOfURL:url encoding:nil error:nil];
 NSRange r = [urlString rangeOfString:@"gratzeez://" options:NSCaseInsensitiveSearch];

    if(r.location != NSNotFound){
        NSLog(@"founddddd");
        NSLog(@"gratzeez url %@",url);
        //NSString *str=[url valueForKey:@"email"];
        NSArray *query = [[url query] componentsSeparatedByString:@"&"];
        NSMutableDictionary *parameters = [NSMutableDictionary dictionaryWithCapacity:[query count]];
        for(NSString *parameter in query)
        {
            NSArray *kv = [parameter componentsSeparatedByString:@"="];
            [parameters setObject:[kv count] > 1 ? [[kv objectAtIndex:1] stringByReplacingPercentEscapesUsingEncoding:NSISOLatin1StringEncoding] : [NSNull null]
                           forKey:[[kv objectAtIndex:0] stringByReplacingPercentEscapesUsingEncoding:NSISOLatin1StringEncoding]];
        }

        NSLog(@"Parameters: %@", parameters);


        [self.tabBar dismissViewControllerAnimated:NO completion:nil];
        RegistrationViewController *RegistrationVC=[[RegistrationViewController alloc] initWithNibName:@"RegistrationViewController" bundle:nil];
        RegistrationVC.txtEmail.userInteractionEnabled=NO;
        NSLog(@"q = %@", [parameters objectForKey:@"email"]);

        UINavigationController *navController=[[UINavigationController alloc]initWithRootViewController:RegistrationVC];
        RegistrationVC.txtEmail.text=[parameters objectForKey:@"email"];
        NSLog(@"value%@",RegistrationVC.txtEmail.text); //here getting null value
        [self.tabBar presentViewController:navController animated:NO completion:nil];
        navController.navigationItem.leftBarButtonItem=nil;
        return YES;

    }

我通过这种方式呈现 registrationviewcontroller 是什么？

RegistrationViewController *RegistrationVC=[[RegistrationViewController alloc] init ];

    NSLog(@"q = %@", [parameters objectForKey:@"email"]);
    UINavigationController *navController=[[UINavigationController alloc]initWithRootViewController:RegistrationVC];

    NSLog(@"txtemail %@ value%@",RegistrationVC.txtEmail,RegistrationVC.txtEmail.text);
    [self.tabBar presentViewController:navController animated:NO completion:^{
        RegistrationVC.txtEmail.userInteractionEnabled=NO;
        RegistrationVC.txtEmail.text=[parameters objectForKey:@"email"];
    }];

现在再次为两者提供 null。

Answer 1

正如我们在评论中看到的，当您尝试为其分配值时，不会创建您的 txtEmail。

我建议您向方法 presentViewController:animated:completion: 添加一个完成 block 。此时，您的 Controller RegistrationVC 将被加载并创建其 View (和 subview )，因此您将能够为您的元素分配值:

[self.tabBar presentViewController:navController animated:NO completion:^{
    RegistrationVC.txtEmail.text=[parameters objectForKey:@"email"];
}];