Four Android Components

The four main components of Android are activity, service, content provider, and broadcast receiver!

Activity: the window for Android program to interact with users. It is the most basic type of Android construction block. It needs to do a lot of persistence to maintain the status of all walks of life, properly manage the lifecycle and some jump Logic

Service: the backend service is activity. It encapsulates a complete functional logic implementation, accepts upper-layer commands, completes related transactions, and defines the intent to be accepted to provide synchronous and asynchronous interfaces.

Content
Provider: a third-party Application Data Access solution provided by Android. It can be derived from the content provider class and provide external data. It can be selected and sorted like a database to shield the storage details of internal data, provides a unified interface model to greatly simplify upper-layer applications and provides a more convenient way to integrate data.

Broadcast
Receiver Er: receives one or more intents as trigger events, receives related messages, performs some simple processing, converts them into a notification, and unifies the Android event broadcast model.