1. Android compatibility problems
There is no need to consider compatibility with the first two versions of Android 1.0 and 1.1.
Some hardware devices with different specifications have emerged since Android 1.6 (highlighted in screen size), which has a certain impact on compatibility.
Features of Android: It is very convenient to interact with hardware, including cameras and GPS. It has its own runtime and virtual machines and excellent memory management capabilities. Provides rich interface controls for developers to use, allows visual development, and ensures applications on the Android platform Program The interface is consistent. Provides a lightweight inter-process communication mechanism. Supports unbounded background service applications.
Supports efficient and fast data access.
Http://www.vogella.de/articles/Android/article.html
An important component of Android.
Activity = the presentation layer of the program, which can have multiple, and can be switched continuously in the application.
Services = a program running in the background without a UI. Starting from Android notification framework
Content Provider = data provision, such as SQLite
Intents = asynchronous information transmission. Ability to request services from other services and interfaces.
Broadcast receiver = accept system information and hidden intents;
Androidmanifest. xml
Description of the current program file, describes the above important components.
R. Java
Describes the resources in the res file. All system resources are stored in the res directory.
Layouts and activities
The description interface of activity is layout. You can useCode, XML definition. It is usually defined in XML.
Activities and lifecyle
The most important lifecycle:
Onsaveinstancestate () is triggered when the activity is stopped. Used to save data
Onpause () ends trigger
Onresume () is triggered when it is restarted.
Context
Used to connect to the Android system.