Question

我有一个带标签栏的应用程序和3个不同的View Controller。其中一个imanage是我通过Interface Builder（storyboard）设计的UItableView，我在Inspector中设置了它的视图控制器类 - ＆gt;检查员身份 - ＆gt;我在那里设置了类字段，因此，当这个视图控制器被实例化时，我无法控制，因为当用户点击标签栏时，它通过故事板完成。请注意，我是目标C和iOS编程的新手。

我面临的问题，我也在使用远程通知。因此，当我在AppDelgate类的“didReceiveRemoteNotification”中收到远程通知消息时。我需要更新UI界面（在ViewController之上），但问题是我没有从我的AppDelgate类到这个ViewController的引用（指针）（或者我？）。这个ViewController由storyboard实例化，也没有以编程方式实现，否则我可以保留对它的引用。

我做了一些阅读，我知道我可以通过NSNotification进行这种沟通，但我认为这对于一个可能出现的问题来说是一种矫枉过正，因为我是新手，我对iOS并不完全了解发展。

谢谢，

Answer 1

NSNotifications易于使用，可能是正确的解决方案。

在需要发送消息的app委托中，只需输入：

[[NSNotificationCenter defaultCenter] postNotificationName:@"MyNotification" object:someObjectYouWantToPassCouldBeAppDelegateOrRemoteNotificationObjectOrAnything];

在接收消息的视图控制器中，输入：

-(void)viewDidLoad
{
    [super viewDidLoad];

    //you can add as many of these as you like to handle different notifications
    [[NSNotificationCenter defaultCenter]  addObserver:self selector:@selector(handleNotification:) name:@"MyNotification" object:nil];
}

-(void)viewDidUnload
{
     //make sure you remove every observer you've added here 
     [[NSNotificationCenter defaultCenter] removeObserver:self name:@"MyNotification" object:nil];

     [super viewDidUnload];
}

-(void)dealloc
{
    //clean up in case viewDidUnload wasn't called (it sometimes isn't) 
    [[NSNotificationCenter defaultCenter] removeObserver:self];
    [super dealloc];
}

//use a different handler method for each notification
//the method name should match the selector in your observe call in viewDidLoad
-(void)handleNotification:(NSNotification *)notification
{
    WhateverClassOfObjectYouWerePassing *object = notification.object;

    //now you have a reference to the object that was passed from your app delegate
}

对于您要调用的不同方法，只需要一个新的通知名称和一个新的处理程序方法。

Answer 2

您的应用代表将有一个指向应用程序窗口的窗口属性。

Window Property具有-rootViewController属性/方法。

对于基于选项卡的应用程序，它会返回TabViewController。

每个TabViewController都有一个方法-(NSArray *)viewControllers，它返回Tab中的ViewControllers。这些按顺序排列。

访问您的应用程序AppDelegate使用[[UIApplication sharedApplication]委托]

一旦你拥有了这些viewcontrollers，你就会知道自从你将它们添加到XIB文件中之后所有这些都是viewController。并且可以执行你的方法

Answer 3

<强> 1。沟通两个ViewControllers

如果您想要传达两个ViewControllers，您应该使用Apple推荐的@protocol：

ViewController1.h

 @interface ViewController1 : UIViewController<ViewController2Delegate, ViewController2DataSource>
@end

ViewController1.m

- (IBAction)goToViewController2:(id)sender{
    if(viewController2 == nil) {
        ViewController2 *viewController = [[ViewController2 alloc]
                                               initWithNibName:@"View2" bundle:[NSBundle mainBundle]];
        viewController2 = viewController;
    }
    //...
    viewController2.delegate = self;
    viewController2.dataSource = self;
    [self.navigationController pushViewController:viewController2 animated:YES];
}


- (NSString)viewController:(ViewController2 *)controller itemForSomethingAtIndex:(NSInteger)index{
    //Send to viewController2 what it needs
    return [items objectAtIndex: index];
}
- (void)viewController:(ViewController2 *)controller didFinishEnteringItem:(NSString *)item{
    //Handle the result from the viewController2
    NSLog(@"result: %@", item);
}

ViewController2.h

#import <UIKit/UIKit.h>


// Define your delegate methods to return items to the delegate of this viewController
@protocol ViewController2Delegate <NSObject>
    - (void)viewController:(ViewController2 *)controller didFinishEnteringItem:(NSString *)item;
@end

// Define your dataSource methods to send items from the dataSource to this viewController
@protocol ViewController2DataSource <NSObject>
    - (NSString)viewController:(ViewController2 *)controller itemForSomethingAtIndex:(NSInteger)index;
@end



@interface ViewController2 : UIViewController

@property (nonatomic) id <ViewController2Delegate> delegate;
@property (nonatomic) id <ViewController2DataSource> dataSource;

@end

ViewController2.m

#import "ViewController2.h"

@interface ViewController2 ()
@end

@implementation ViewController2

@synthesize //...;

- (void)someMethod {
    //Get someThing from controller1
    NSString *item = [dataSource viewController: self itemForSomethingAtIndex:0];

    //Return someThing to controller1
    [delegate viewController: self didFinishEnteringItem: item];
}

<强> 2。使用viewController传递backgroundTask

如果您想传达后台任务或处理推送通知，请使用@ NickLockwood的answer。但如果viewController没有加载，这不会工作。在这种情况下，您应该在AppDelegate中处理它：

//Get the appDelegate instance
AppDelegate *appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
//And call your custom method to show what it needs
[appDelegate customMethod];

您的自定义方法应该像控制器一样调用控制器：

AppDelegate > RootController > ViewController1 > ViewController2 > myMethod 
//do something if viewController2 is visible to the user or push it before do something.
//if you use navigation controller, then you need to ask for the position and className

两个不同的视图控制器如何相互通信

3 个答案: