检测首次推出的iOS应用

Question

我试图在Swift中找到一种方法来检测第一次发射.

Answer 1

通常,您会向NSUserDefaults写一个值,以指示之前已启动的应用程序.

let launchedBefore = NSUserDefaults.standardUserDefaults().boolForKey("launchedBefore")
if launchedBefore  {
    print("Not first launch.")
}
else {
    print("First launch, setting NSUserDefault.")
    NSUserDefaults.standardUserDefaults().setBool(true, forKey: "launchedBefore")
}

更新 - 斯威夫特3

let launchedBefore = UserDefaults.standard.bool(forKey: "launchedBefore")
if launchedBefore  {
    print("Not first launch.")
} else {
    print("First launch, setting UserDefault.")
    UserDefaults.standard.set(true, forKey: "launchedBefore")
}

Answer 2

我总是需要这个,所以我把它放在一个类别中

一般用法:

let isFirstLaunch = UserDefaults.isFirstLaunch()

AppDelegate中的用法

// use this if you need to refer to it later
var optionallyStoreTheFirstLaunchFlag = false

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        optionallyStoreTheFirstLaunchFlag = UserDefaults.isFirstLaunch()
   // .. do whatever else

    return true
}

一些重要的考虑:

• 此标志仅在第一次调用时设置.如果您想在不同的屏幕中多次了解第一次启动,请根据"optionalStoreTheFirstLaunchFlag"示例设置您稍后可以参考的变量.
• 在iOS中,应用程序通常永远不会关闭.应用程序背景,前置,状态保存到闪存,但只有当用户强制关闭(罕见)或用户重新启动手机时,才会重新启动应用程序.因此,如果将其存储在变量中,它可能会长时间存在.完成所有教程屏幕和诸如此类的操作后,手动重置它.

斯威夫特4

将以下内容放在UserDefaults + isFirstLaunch.swift中

extension UserDefaults {
    // check for is first launch - only true on first invocation after app install, false on all further invocations
    // Note: Store this value in AppDelegate if you have multiple places where you are checking for this flag
    static func isFirstLaunch() -> Bool {
        let hasBeenLaunchedBeforeFlag = "hasBeenLaunchedBeforeFlag"
        let isFirstLaunch = !UserDefaults.standard.bool(forKey: hasBeenLaunchedBeforeFlag)
        if (isFirstLaunch) {
            UserDefaults.standard.set(true, forKey: hasBeenLaunchedBeforeFlag)
            UserDefaults.standard.synchronize()
        }
        return isFirstLaunch
    }
}

Answer 3

我提炼了一点用户n13的答案

• 让方法在第一次启动时始终返回true
• 是UIApplication的扩展

只需在任何地方使用它,UIApplication.isFirstLaunch()并确保在首次执行期间至少达到一次.

斯威夫特3

import UIKit

private var firstLaunch : Bool = false

extension UIApplication {

    static func isFirstLaunch() -> Bool {
        let firstLaunchFlag = "isFirstLaunchFlag"
        let isFirstLaunch = UserDefaults.standard.string(forKey: firstLaunchFlag) == nil
        if (isFirstLaunch) {
            firstLaunch = isFirstLaunch
            UserDefaults.standard.set("false", forKey: firstLaunchFlag)
            UserDefaults.standard.synchronize()
        }
        return firstLaunch || isFirstLaunch
    }
}

斯威夫特2

import UIKit

private var firstLaunch : Bool = false

extension UIApplication {

    static func isFirstLaunch() -> Bool {
        let firstLaunchFlag = "isFirstLaunchFlag"
        let isFirstLaunch = NSUserDefaults.standardUserDefaults().stringForKey(firstLaunchFlag) == nil
        if (isFirstLaunch) {
            firstLaunch = isFirstLaunch
            NSUserDefaults.standardUserDefaults().setObject("false", forKey: firstLaunchFlag)
            NSUserDefaults.standardUserDefaults().synchronize()
        }
        return firstLaunch || isFirstLaunch
    }
}

Answer 4

迅捷3

extension UserDefaults {

     var hasLaunchBefore: Bool {
           get {
             return self.bool(forKey: #function)
           }
           set {
             self.set(newValue, forKey: #function)
           }
     }
}

Swift 5（属性包装器）

UserDefaultWrapper：

@propertyWrapper
struct UserDefaultWrapper<T> {
    let key: String
    let defaultValue: T

    init(_ key: String, defaultValue: T) {
        self.key = key
        self.defaultValue = defaultValue
    }

    var wrappedValue: T {
        get {
            return UserDefaults.standard.object(forKey: key) as? T ?? defaultValue
        }
        set {
            UserDefaults.standard.set(newValue, forKey: key)
        }
    }
}

UserDefaultsStore：

struct UserDefaultsStore {
    @UserDefaultWrapper("has_launch_before", defaultValue: false)
    static var hasLaunchBefore: Bool
}

用法：

UserDefaultsStore.hasLaunchBefore = false

Answer 5

使用NSUserDefaults。注册一个值为 的 BOOL 键false。在启动时读取密钥；如果是false，请将其设置为true并表示欢迎。下次启动时，您将true不再表示欢迎，问题已解决。