App Extension

iOS and macOS define several types of app extensions, each of which is tied to a single, well-scoped area of the system. A system area that enables extensions is called an extension point.

An app extension is different from an app. Although you must use an app to contain and deliver your extensions, each extension is a separate binary that runs independent of the app used to deliver it.

You create an app extension by adding a new target to an app. You can add multiple extension targets to a single app (an app that contains one or more extensions is called a containing app).

An app that a user employs to choose an app extension is called a host app. An app extension communicates primarily with its host app. Any app extension and its containing app can access shared data in a privately defined shared container.

A Today widget (and no other app extension type) can ask the system to open its containing app by calling the openURL:completionHandler: method of the NSExtensionContext class.

Each app extension template includes a property list file (that is, an Info.plist file), a view controller class, and a default user interface, all of which are defined by the extension point.

When a host app sends a request to an app extension, it specifies an extension context.

如何调试？In your extension scheme’s Run phase, you specify a host app as the executable.

数据共享 To enable data sharing, use Xcode or the Developer portal to enable app groups for the containing app and its contained app extensions.

上传与下载 In iOS, if your extension isn’t running when a background task completes, the system launches your containing app in the background and calls the application:handleEventsForBackgroundURLSession:completionHandler: app delegate method.

If your app extension initiates a background NSURLSession task, you must also set up a shared container that both the extension and its containing app can access. Use the sharedContainerIdentifier property of the NSURLSessionConfiguration class to specify an identifier for the shared container so that you can access it later.

开启完全访问 定位服务、地址簿、与宿主 APP 共享容器、网络请求/云输入等……

To ask the system to switch to another keyboard, call the advanceToNextInputMode method of the UIInputViewController class. The system picks the appropriate “next” keyboard from the list of user-enabled keyboards; there is no API to obtain a list of enabled keyboards or for picking a particular keyboard to switch to. 不能切换到指定输入法