objective-c - 将 UINavigationController 添加到窗口时出现 EXC_BAD_ACCESS

Question

我正在开发一个使用多个 View Controller 和导航 Controller 的应用程序。当应用程序运行并执行以下代码时，它会在尝试添加 subview 时抛出异常。

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    [self.window addSubview:[navigationController view]];
    [self.window makeKeyAndVisible];
}

我这样声明导航 Controller :

@interface SimpleContactsAppDelegate : NSObject <UIApplicationDelegate> {
    NSManagedObjectModel *managedObjectModel;
    NSManagedObjectContext *managedObjectContext;
    NSPersistentStoreCoordinator *persistentStoreCoordinator;

    UIWindow *window;  
    UINavigationController *navigationController;
    // view for adding new contacts
    UIViewController *newContactView;
    UIButton *addButton;

    // controls for the addContactView
    UIButton *saveContactButton;
    UITextField *nameField;
    UITextField *emailField;
    UITextField *phoneField;

    UITableView *contactsTable;
}
@property (nonatomic, retain, readonly) NSManagedObjectModel *managedObjectModel;  
@property (nonatomic, retain, readonly) NSManagedObjectContext *managedObjectContext;  
@property (nonatomic, retain, readonly) NSPersistentStoreCoordinator *persistentStoreCoordinator;

@property (nonatomic, retain) IBOutlet UIWindow *window;
@property (nonatomic, retain) IBOutlet UINavigationController *navigationController;

@property (nonatomic, retain) IBOutlet UIButton *addButton;
@property (nonatomic, retain) IBOutlet UITableView *contactsTable;

// controller and fields for the form
@property (nonatomic, retain) IBOutlet UIViewController *newContactView;
@property (nonatomic, retain) IBOutlet UITextField *nameField;
@property (nonatomic, retain) IBOutlet UITextField *emailField;
@property (nonatomic, retain) IBOutlet UITextField *phoneField;
@property (nonatomic, retain) IBOutlet UIButton *saveContactButton;

我已将导航 Controller 连接到 XIB 中的委托(delegate)对象。请随时查看我的完整来源:https://github.com/agmcleod/SimpleContacts/tree/parttwo

我试过将 Instruments 与 NSZombie 一起使用，但它似乎并没有停下来让我检查具体出了什么问题。它有时也会继续运行，不会终止。我最终不得不使用事件终端强制退出它。

Answer 1

首先，您声明一个属性，但通过其实例变量而不是使用该属性访问 UINavigationController。

使用这个:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    [self.window addSubview:[self.navigationController view]];
    [self.window makeKeyAndVisible];
    return YES;
}

其次，您将主要 nib 文件的名称更改为“Window.xib”。您要么必须将其改回“MainWindow.xib”，要么必须编辑 SimpleContacts-Info.plist 并将“Main nib file base name”的值更改为“Window”。