objective-c - 使用 Storyboard 时，从 appdelegate 调用 View Controller 方法不起作用

Question

大家好

使用 Storyboard时，我无法在我的 ViewController 中调用刷新方法。但是，如果我创建的项目没有 Storyboard ，只有一个 NIB，它就可以工作。为什么它不起作用以及如何解决这个问题？

这是我的代码:

AppDelegate.h

#import <UIKit/UIKit.h>

@class ViewController;


@interface AppDelegate : NSObject <UIApplicationDelegate>
{
    UIWindow *window;
    ViewController *viewController;
}

@property (nonatomic, retain) IBOutlet UIWindow *window;
@property (nonatomic, retain) IBOutlet ViewController *viewController;

@end

AppDelegate.m

#import "AppDelegate.h"
#import "ViewController.h"

@implementation AppDelegate

@synthesize window;
@synthesize viewController;

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    // Override point for customization after application launch.
    return YES;
}

- (void)applicationWillResignActive:(UIApplication *)application
{
    // Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
    // Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.
}

- (void)applicationDidEnterBackground:(UIApplication *)application
{
    // Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later. 
    // If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
}

- (void)applicationWillEnterForeground:(UIApplication *)application
{
    // Called as part of the transition from the background to the inactive state; here you can undo many of the changes made on entering the background.
    NSLog(@"app will enter foreground");
    [viewController refresh:NULL]; 
}

- (void)applicationDidBecomeActive:(UIApplication *)application
{
    // Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
}

- (void)applicationWillTerminate:(UIApplication *)application
{
    // Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
}

@end

ViewController.h

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController

-(IBAction) refresh:(id)sender;

@end

ViewController.m

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

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

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}

- (void)loadData {
    // contains information the ViewController makes use of
}

-(IBAction)refresh:(id) sender {
    [self loadData];
}

@end

Answer 1

使用 Storyboard时，不会填充应用程序委托(delegate)中的 viewController 属性。在您的日志语句中包含该值以进行确认 - 它将为空。

改为为通知注册您的 View Controller ，并让它处理自己的刷新。

在viewDidLoad中:

[super viewDidLoad];
[[NSNotificationCenter defaultCenter] addObserver:self 
    selector:@selector(refresh:) 
    name:UIApplicationDidBecomeActiveNotification
    object: nil];

您还需要在 dealloc/viewDidUnload 中删除此观察者。