有什么方法可以检查iOS应用是否在后台？

我想检查应用程序是否在后台运行。

在：

locationManagerDidUpdateLocation {
    if(app is runing in background){
        do this
    }
}

应用程序委托获取指示状态转换的回调。您可以基于此进行跟踪。

UIApplication中的applicationState属性也返回当前状态。

[[UIApplication sharedApplication] applicationState]

UIApplicationState state = [[UIApplication sharedApplication] applicationState];
if (state == UIApplicationStateBackground || state == UIApplicationStateInactive)
{
   //Do checking here.
}

这可以帮助您解决问题。

请参阅下面的评论-非活动状态是一种非常特殊的情况，可能意味着该应用程序正在启动中。根据您的目标，这可能对您意味着“背景”。

迅捷3

    let state = UIApplication.shared.applicationState
    if state == .background {
        print("App in Background")
    }

迅捷版：

let state = UIApplication.sharedApplication().applicationState
if state == .Background {
    print("App in Background")
}

如果您希望接收回调而不是“询问”应用程序状态，请在您的中使用以下两种方法AppDelegate：

- (void)applicationDidBecomeActive:(UIApplication *)application {
    NSLog(@"app is actvie now");
}


- (void)applicationWillResignActive:(UIApplication *)application {
    NSLog(@"app is not actvie now");
}

迅捷5

let state = UIApplication.shared.applicationState
    if state == .background {
        print("App in Background")
        //MARK: - if you want to perform come action when app in background this will execute 
        //Handel you code here
    }
    else if state == .foreground{
        //MARK: - if you want to perform come action when app in foreground this will execute 
        //Handel you code here
    }

迅捷4+

let appstate = UIApplication.shared.applicationState
        switch appstate {
        case .active:
            print("the app is in active state")
        case .background:
            print("the app is in background state")
        case .inactive:
            print("the app is in inactive state")
        default:
            print("the default state")
            break
        }

一个Swift 4.0扩展，使访问起来更加容易：

import UIKit

extension UIApplication {
    var isBackground: Bool {
        return UIApplication.shared.applicationState == .background
    }
}

要从您的应用内访问：

let myAppIsInBackground = UIApplication.shared.isBackground

如果您正在寻找在各种状态信息（active，inactive和background），你可以找到这里的苹果文档。