我是 Objective-C 编程的初学者。 我在这里和其他网站上搜索了解决问题的方法，但没有找到。 我想在系统加载之前创建一个登录 View 。然后，登录后我想关闭它。 在我的项目中，我使用 ARC 而不是 Storyboards。

当我调试并查看函数“efetuarLogin”时，属性委托(delegate)的值为 0x000000。我认为它是空白的，不是吗？ 根据我在互联网上找到的教程和其他提示，这是代码委托(delegate)的正确方法。你能帮我检查一下吗？ 这是代码:

登录.h

#import <UIKit/UIKit.h>
@class Login;

@protocol LoginDelegate <NSObject>
@required
    - (void)loginDidFinish: (Login *)login;
@end

@interface Login : UIViewController{
    __weak id<LoginDelegate> delegate;
}

@property (nonatomic, weak) id <LoginDelegate> delegate;

- (IBAction)efetuarLogin:(id)sender;

@end

登录.M

#import "Login.h"

@implementation Login
@synthesize delegate;

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

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (IBAction)efetuarLogin:(id)sender {
    [delegate loginDidFinish:self];
}
@end

主 Controller .h

#import <UIKit/UIKit.h>
#import "Login.h"

@interface MainController : UITabBarController <LoginDelegate>

@end

主 Controller .m

#import "MainController.h"
#import "Login.h"
#import "ModalViews.h"
#import "Alerts.h"
#import "ViewPadrao.h"
#import "TableView.h"

@implementation MainController

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

- (void)viewDidLoad
{
    [super viewDidLoad];

    ModalViews *modalViews = [[ModalViews alloc] initWithNibName:@"ModalViews" bundle:nil];
    Alerts *alerts = [[Alerts alloc] initWithNibName:@"Alerts" bundle:nil];
    ViewPadrao *viewPadrao = [[ViewPadrao alloc] initWithNibName:@"ViewPadrao" bundle:nil];
    TableView *tableView = [[TableView alloc] initWithNibName:@"TableView" bundle:nil];

    self.viewControllers = @[modalViews, alerts, viewPadrao, tableView];
}
- (void)viewDidAppear:(BOOL)animated{
    [super viewDidAppear:animated];

    Login *login = [[Login alloc] initWithNibName:@"Login" bundle:nil];
    [login setModalTransitionStyle:UIModalTransitionStyleCoverVertical];
    [self presentViewController:login animated:NO completion:nil];
}
- (void)loginDidFinish: (Login *)login{
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Sua mensagem aqui" message:@"Mensagem" delegate:self cancelButtonTitle:@"Fechar" otherButtonTitles:nil];
    [alert show];
    [self dismissViewControllerAnimated:YES completion:nil];
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

以及AppDelegate.m的didFinishLaunchingOptions方法:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

    mainController = [[MainController alloc] init];

    window.rootViewController = mainController;

    [window makeKeyAndVisible];

    return YES;
}

抱歉，代码量太大。我已经很感激了!!

我正在使用 ViewDidAppear 方法向用户显示登录信息。但是当我关闭并且 MainController 出现时，方法 viewdidapper 再次创建登录。 我该怎么做才能显示登录一次？当我尝试在 viewdidload 上执行此操作时，它不起作用。登录没有出现。

最佳答案

在您的 MainViewController.m 中创建 login 对象

- (void)viewDidAppear:(BOOL)animated{
    [super viewDidAppear:animated];

    Login *login = [[Login alloc] initWithNibName:@"Login" bundle:nil];
    login.delegate = self;  //add this line
    [login setModalTransitionStyle:UIModalTransitionStyleCoverVertical];
    [self presentViewController:login animated:NO completion:nil];
}

编辑:在问题中看到 OP 的编辑后(应该是不同的线程)

您的 View Controller 层次结构是错误的。理想的流程应该是

1) 直接从 App delegate 显示登录 Controller 。

2) 登录成功后，从登录 Controller 显示MainViewController。

关于objective-c - 使用 ARC 的自定义委托(delegate) iOS 6 无法正常工作，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/14133623/