启动时在ios模拟器中显示空白/黑屏

Question

我正在尝试向coredata输入用户信息，以便我可以将它发送到我的php并执行MySQL登录。然而，当我测试只是coredata部分时，我所得到的只是一个黑屏/空白屏幕，没有xcode错误或错误报告（在自定义图像加载屏幕后，应该有我的背景和我的按钮）。下面是我的代码，显然排除故事板和xcdatamodeld（实际存储核心数据输入）。我做错了什么？

Appdelegate.h

#import <UIKit/UIKit.h> 

@class LoginViewController; 

@interface AppDelegate : UIResponder <UIApplicationDelegate> 
{ 
    LoginViewController *viewController; 
} 
@property (strong, nonatomic) IBOutlet LoginViewController *viewController; 
@property (strong, nonatomic) UIWindow *window; 
@property (readonly, strong, nonatomic) NSManagedObjectContext *managedObjectContext; 
@property (readonly, strong, nonatomic) NSManagedObjectModel *managedObjectModel; 
@property (readonly, strong, nonatomic) NSPersistentStoreCoordinator *persistentStoreCoordinator; 
- (void)saveContext; 

@end 

Appdelegate.m

#import "AppDelegate.h" 

@implementation AppDelegate 

@synthesize window = _window; 
@synthesize managedObjectContext = __managedObjectContext; 
@synthesize managedObjectModel = __managedObjectModel; 
@synthesize persistentStoreCoordinator = __persistentStoreCoordinator; 
@synthesize viewController; 

- (BOOL)application:(UIApplication *)application 
didFinishLaunchingWithOptions:(NSDictionary *)launchOptions 
{ 
    self.window = [[UIWindow alloc] 
        initWithFrame:[[UIScreen mainScreen] bounds]]; 
    [self.window makeKeyAndVisible]; 
    return YES; 
} 

LoginViewController.h

#import <UIKit/UIKit.h> 

    @interface LoginViewController : UIViewController { 
     UITextField *username; 
     UITextField *password; 

    } 
    @property (strong, nonatomic) IBOutlet UITextField *username; 
    @property (strong, nonatomic) IBOutlet UITextField *password; 
    - (IBAction)saveData:(id)sender; 

@end 

LoginViewController.m

#import "LoginViewController.h" 
#import "AppDelegate.h" 
#import "Contacts.h" 

@interface LoginViewController() 

@end 

@implementation LoginViewController 

@synthesize username, password; 


- (IBAction)saveData:(id)sender { 

    AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate]; 

    NSManagedObjectContext *context = [appDelegate managedObjectContext]; 

    NSManagedObject *newContact; 

    newContact = [NSEntityDescription insertNewObjectForEntityForName:@"Contacts" inManagedObjectContext:context]; 

    [newContact setValue:username.text forKey:@"username"]; 
    [newContact setValue:password.text forKey:@"password"]; 

    username.text = @""; 
    password.text = @""; 

    NSError *error; 
    [context save:&error]; 
} 

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil 
{ 
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]; 
    if (self) { 
     // Custom initialization 
    } 
    return self; 
} 
@end 

Contacts.h

#import <Foundation/Foundation.h> 
#import <CoreData/CoreData.h> 


@interface Contacts : NSManagedObject 

@property (nonatomic, retain) NSString * username; 
@property (nonatomic, retain) NSString * password; 


@end 

Contacts.m

#import "Contacts.h" 


@implementation Contacts 

@dynamic username; 
@dynamic password; 


@end 

Answer 1

原因是，你是不是在你的窗口中添加任何viewcontrollers。

只需添加您的LoginController就可以了，

像

- (BOOL)application:(UIApplication *)application 
didFinishLaunchingWithOptions:(NSDictionary *)launchOptions 
{ 
     self.window = [[UIWindow alloc] 
       initWithFrame:[[UIScreen mainScreen] bounds]]; 
     [self.window addSubView:viewController.view]; 
     // OR self.window.rootController = viewController; 
     [self.window makeKeyAndVisible]; 
     return YES; 

}