Android learning notes (1) Overview

1 Overview

This series of articles mainly records some experiences in Android, mainly focusing on underlying development (including bootloader, kernel, driver, etc.), and will inevitably involve the introduction of relevant hardware ).

1.1 System Framework

The Android system framework is as follows:

1.1.1 Application

Android is released together with a series of core application packages, including the email client, SMS Short Message program, calendar,

Maps, browsers, and contact management programs. All applications are written in Java.

1.1.2 Application Framework

Developers can also fully access the API framework used by core applications. The architecture design of this application simplifies Component reuse; any application can publish its functional blocks, and any other application can use the released functional blocks.

Rack security restrictions ). Similarly, this application reuse mechanism allows you to easily replace program components.

A series of services and systems are hidden behind each application, including;

Rich and scalable views: these views can be used to build applications, including lists, grids, and text boxes), buttons (buttons), or even embedded web browsers;

Ø content providers: enables applications to access data of another application (such as the contact database) or share their own data;

Ø Resource Manager: provides access to non-code resources, such as local strings, images, and layout files );

Notification MANAGER: enables applications to display custom prompts in the status bar;

Activity MANAGER: used to manage the application lifecycle and provides common navigation rollback functions;

1.1.3 Library

Android contains some C/C ++ libraries that can be used by different components in the Android system. They provide services to developers through the Android Application Framework. The following are some core databases:

System C Library: a standard C system function library (libc) inherited from BSD, which is specially customized for embedded linux devices;

Media Library: Based on PacketVideo OpenCORE. This library supports multiple common audio and video formats for playback and recording, as well as static image files. The encoding formats include MPEG4, H.264, MP3, AAC, AMR, JPG, and PNG;

Ø Surface Manager: manages the display subsystem and provides seamless integration of 2D and 3D layers for multiple applications;

LibWebCore: The latest web browser engine. It supports Android browsers and an embedded web View;

Ø SGL: underlying 2D graphics engine;

3D libraries: implemented based on OpenGL ES 1.0 APIs. This library can use hardware 3D acceleration (if available) or highly optimized 3D soft acceleration;

Ø FreeType: displays bitmap and vector Fonts;

SQLite: a lightweight relational database engine that is available and powerful for all applications;

1.1.4 Android Runtime Library

Android includes a core library that provides most of the functions of the core library of JAVA programming language.

Every android application runs in its own process and has an independent Dalvik Virtual Machine instance. Dalvik is designed as a device to efficiently run multiple virtual systems at the same time. Dalvik executable files executed by the Dalvik Virtual Machine (. Dex), which are optimized for small memory usage. At the same time, the virtual machine is register-based. All classes are compiled by the Java compiler, and then converted to the. Dex format using the "dx" tool in the SDK is executed by the virtual machine.

The Dalvik virtual machine depends on some features of the Linux kernel, such as the thread mechanism and the underlying memory management mechanism.

1.1.5 Linux Kernel

Android core system services depend on the Linux 2.6 kernel, such as security, memory management, process management, network protocol stack and driver model.

The Linux kernel is also an abstraction layer between the hardware and software stacks.

1.2 document structure

The current plan is as follows:

Introduction to Android and acquisition of Android Resources;

Ø entry: Build the development platform and demonstrate the development of the android program with a simple hello program;

Ø Bootloader: we mainly discuss porting U-boot on the 6410 Development Board;

Ø kernel: we mainly discuss Linux porting on the 6410 Development Board;

Ø DRIVER: Mainly discusses some drivers developed on the 6410 Development Board;

Ø middleware:

Application: