iOS如何判断应用程序是运行前台还是后台？ [英] iOS how to judge application is running foreground or background?

问题描述

众所周知，如果iOS应用程序正在运行前台，那么应用程序将不会在删除通知到来时通知用户。现在在我的应用程序中，我想显示警报以通知用户远程通知到来。如何判断应用程序是运行前台还是后台？我找到了docs并搜索了stackoverflow.com，却找不到任何相关内容。
谢谢。

As we all knows, if an iOS app is running foreground, then the app won't notify users when the remove notification come. Now In my app, I want to show alert to notify users that remote notification comes. How to judge if the app is running foreground or background? I have found the docs and searched stackoverflow.com and failed to find any thing about that. Thank you.

推荐答案

[UIApplication sharedApplication] .applicationState 将返回当前状态，检查可能的值，并且在您可以使用系统功能时不要创建不必要的标记。

[UIApplication sharedApplication].applicationState will return current state, check it possible values and don't create unnecessary flags when you can use system features.

您可能要考虑的值：

• UIApplicationStateActive


• UIApplicationStateInactive


• UIApplicationStateBackground

例如

+(BOOL) runningInBackground
{
    UIApplicationState state = [UIApplication sharedApplication].applicationState;
    return state == UIApplicationStateBackground;
}

+(BOOL) runningInForeground
{
    UIApplicationState state = [UIApplication sharedApplication].applicationState;
    return state == UIApplicationStateActive;
}

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