Principles and introduction to broadcasting, services, databases, notifications, packages, etc. in Android (illustrated) _android

Brief introduction

There are many mechanisms used in Android, such as broadcasting, services, databases, notifications, packages ... Wait a minute.

What is a broadcast? Broadcast is a widely used mechanism for transmitting information between applications. Similar to radio stations, which receive delivery according to specific frequencies.

What is a service? Service is one of the four major components of the Android system, which is the same as the activity level, but cannot run only in the background and can interact with other components. Use occasions such as: background music player.

What database was used? Open Source project SQLite operational data is used in Android. The SQLite database is an open source embedded database written by D.richard Hipp in C language, with a supported database size of 2TB.

What notice? Notification is a commonly used form of notification in Android, when there are unread messages or not answering the phone, the screen status bar will have a hint icon, you can drop the status bar to read the notification.

What is a bag? Android applications all have packages, which are descriptions of programs.

Details

1. Broadcast Broadcastreceiver

2, service services

Life cycle

3. Database ContentProvider

4, notice column Notification

5, Package Packages

The management class for packages in Android is Packagemanager.

The framework is as follows: