Question

在我的主要应用类别中,我有<条码> 查询/编码>议定书,其中界定了<条码>应用DidBecomeActive方法。

我想在申请从背景返回时采用一种方法,但这种方法在另一种观点是控制器。我如何检查一下在<编码>应用DidBecomeActive方法中目前显示的哪位控制器,然后对该控制器内的一种方法发出呼吁?

Answer 1

申请中的任何类别均可成为申请中不同通知的“观察员”。当你创建(或装载)你的视力控制器时,你希望将其登记为<代码>的观察员。 UIApplication DidBecomeActiveNotification,并具体说明,当通知送交你申请时,你想要采用哪种方法。

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

Don! 在你看来即将消失时,请删除其观察员:

[[NSNotificationCenter defaultCenter] removeObserver:self 
                                                name:UIApplicationDidBecomeActiveNotification
                                              object:nil];

关于。

Answer 2

<>Swift 3, 4 Equivalent:

增加观察员

NotificationCenter.default.addObserver(self,
    selector: #selector(applicationDidBecomeActive),
    name: .UIApplicationDidBecomeActive, // UIApplication.didBecomeActiveNotification for swift 4.2+
    object: nil)

观察员

NotificationCenter.default.removeObserver(self,
    name: .UIApplicationDidBecomeActive, // UIApplication.didBecomeActiveNotification for swift 4.2+
    object: nil)

反馈

@objc func applicationDidBecomeActive() {
    // handle event
}

Answer 3

<>Swift 2 Equivalent:

let notificationCenter = NSNotificationCenter.defaultCenter()

// Add observer:
notificationCenter.addObserver(self,
  selector:Selector("applicationWillResignActiveNotification"),
  name:UIApplicationWillResignActiveNotification,
  object:nil)

// Remove observer:
notificationCenter.removeObserver(self,
  name:UIApplicationWillResignActiveNotification,
  object:nil)

// Remove all observer for all notifications:
notificationCenter.removeObserver(self)

// Callback:
func applicationWillResignActiveNotification() {
  // Handle application will resign notification event.
}

Answer 4

<>Swift 5

fileprivate  func addObservers() {
      NotificationCenter.default.addObserver(self,
                                             selector: #selector(applicationDidBecomeActive),
                                             name: UIApplication.didBecomeActiveNotification,
                                             object: nil)
    }

fileprivate  func removeObservers() {
        NotificationCenter.default.removeObserver(self, name: UIApplication.didBecomeActiveNotification, object: nil)
    }

@objc fileprivate func applicationDidBecomeActive() {
// here do your work
    }

Answer 5

<>Swift 4.2

增加观察员

NotificationCenter.default.addObserver(self, selector: #selector(handleEvent), name: UIApplication.didBecomeActiveNotification, object: nil)

移走观察员

NotificationCenter.default.removeObserver(self, name: UIApplication.didBecomeActiveNotification, object: nil)

活动

@objc func handleEvent() {
}

Answer 6

迅速,4个 Apple果通过新的汇编者警告说,我们避免在这种情形下使用<代码>#sctorele。以下是实现这一目标的更安全途径:

首先,会产生一个可视旁听的变量(将用于取消观察员):

var didBecomeActiveObserver: NSObjectProtocol

之后,通知可使用 la:

lazy var didBecomeActive: (Notification) -> Void = { [weak self] _ in
    // Do stuff
}

如您要求列入实际通知,仅将<代码>_改为notification/code>。


其次,我们设立了这一通知,以观察这项通知是否积极。
func setupObserver() {
    didBecomeActiveObserver = NotificationCenter.default.addObserver(
                                  forName: UIApplication.didBecomeActiveNotification,
                                  object: nil,
                                  queue:.main,
                                  using: didBecomeActive)
}

这里的重大变化是,我们现在不使用#selector,而是称之为上文所创造的var。 这可以消除你失职的挑选人员坠毁的情况。
最后,我们排除了观察员。
func removeObserver() {
    NotificationCenter.default.removeObserver(didBecomeActiveObserver)
}

Answer 7

<Swift 5 edition:

 NotificationCenter.default.addObserver(self,
                                               selector: #selector(loadData),
                                               name: UIApplication.didBecomeActiveNotification,
                                               object: nil)

移除观察员在9年及以后。

Answer 8

页: 1

override func viewWillAppear(_ animated: Bool) {
         super.viewWillAppear(animated)

         NotificationCenter.default.addObserver(self, selector: #selector(applicationWillResignActive), name: UIApplication.willResignActiveNotification, object: nil)
    
         NotificationCenter.default.addObserver(self, selector: #selector(applicationDidBecomeActive), name: UIApplication.didBecomeActiveNotification, object: nil)
        }
    
    override func viewWillDisappear(_ animated: Bool) { 
        super.viewWillDisappear(animated)

        NotificationCenter.default.removeObserver(self, name: UIApplication.willResignActiveNotification, object: nil)

        NotificationCenter.default.removeObserver(self, name: UIApplication.didBecomeActiveNotification, object: nil)
    }


@objc private func applicationWillResignActive() {
    }

    @objc private func applicationDidBecomeActive() {
    }

Answer 9

The Combine way:

import Combine

var cancellables = Set<AnyCancellable>()
NotificationCenter.default.publisher(for: UIApplication.didBecomeActiveNotification)
    .sink { notification in
            // do stuff
    }.store(in: &cancellables)

Answer 10


www.un.org/Depts/DGACM/index_spanish.htm 更快速的5+解决办法

添加以下观察员:<条码>init或viewDidLoad:

NotificationCenter.default.addObserver(self, 
                                       selector: #selector(appDidBecomeActive),
                                       name: UIApplication.didBecomeActiveNotification,
                                       object: nil)

如其他答复所示,你不需要去除观察员。自动完成。

@objc private func appDidBecomeActive() {
    // do your magic
}

Answer 11

如果有的话,请迅速调查:

.onReceive(NotificationCenter.default.publisher(
    for: UIApplication.didBecomeActiveNotification)) { _ in
        print("DID BECOME ACTIVE")
    }
)

Answer 12

Swift5 MacOS, 你需要使用NSApplication,而不是UIApplication。

NotificationCenter.default.addObserver(self,
                                       selector: #selector(applicationDidBecomeActive),
                                       name: (NSApplication.didBecomeActiveNotification),
                                       object: nil)
    }

友情链接