iOS - 从后台自动打开应用程序

Question

是否可以以某种方式从后台模式重新打开应用程序？例如，如果后台应用程序正在检查服务器上的某些标志，然后当触发时，它会自动转到前台？

如果没有，我可以显示一条消息并播放声音以供用户请求重新打开应用程序吗？

例如 WhatsApp 如何实现这一目标？

Answer 1

无法自动打开应用程序，即向用户显示应用程序。

但是，可以使用推送通知在后台打开您的应用程序，以便它可以执行简短的任务。这是通过创建 push notification 来实现的。与 content-available 字段。

If your server sends push notifications to a user’s device when new content is available for your app, you can ask the system to run your app in the background so that it can begin downloading the new content right away. The intent of this background mode is to minimize the amount of time that elapses between when a user sees a push notification and when your app is able to able to display the associated content. Apps are typically woken up at roughly the same time that the user sees the notification but that still gives you more time than you might have otherwise.

To support this background mode, enable the Remote notifications option from the Background modes section of the Capabilities tab in your Xcode project. (You can also enable this support by including the UIBackgroundModes key with the remote-notification value in your app’s Info.plist file.)

For a push notification to trigger a download operation, the notification’s payload must include the content-available key with its value set to 1. When that key is present, the system wakes the app in the background (or launches it into the background) and calls the app delegate’s application:didReceiveRemoteNotification:fetchCompletionHandler: method. Your implementation of that method should download the relevant content and integrate it into your app.

When downloading any content, it is recommended that you use the NSURLSession class to initiate and manage your downloads. For information about how to use this class to manage upload and download tasks, see URL Loading System Programming Guide.

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can i display a message and play sound for the user to request app reopen?

是的，您可以只使用Local Notification or a Push Notification