Android Basics Getting Started tutorial--1.1 background correlation and system architecture analysis

Android Basics Getting Started tutorial--1.1 background correlation and system architecture analysis

Tags: Android basics Getting Started Tutorial

1.Android background with current situation

The Android system was created by Andy Rubin and was later acquired by Google; The earliest version is: Android 1.1 version
And now the latest version of this year's 5.28,google I/O conference launched Android M, it is interesting that the name of the Android system is named after the dim sum, the following table is 15 Android version name, corresponding API number and release time!

System version Name	API Version Number	Release Time
Android 1.5:cupcake: Cupcakes	3	2009.4.30
Android 1.6:donut: Donuts	4	2009.9.15
Android 2.0/2.0.1/2.1:eclair: Muffins	5/6/7	2009.10.26
Android 2.2/2.2.1:froyo: Frozen Yogurt	8	2010.5.20
Android 2.3:gingerbread: Ginger pie	9	2010.12.7
Android 3.0:honeycomb: Hive	11	2011.2.2
Android 3.1:honeycomb: Hive	12	2011.5.11
Android 3.2:honeycomb: Hive	13	2011.7.13
Android 4.0:ice Cream Sandwich: Ice Cream Sandwich	14	2011.10.19
Android 4.1:jelly bean: Jelly bean	16	2012.6.28
Android 4.2:jelly bean: Jelly bean	17	2012.10.30
Android 4.3:jelly bean: Jelly bean	18	2013.7.25
Android 4.4:kitkat: Kit Kat Chocolate	19	2013.11.01
Android 5.0:donut: Lollipop	21st	2014.10.16
Android M: Preview version	22	2015.5.28

Well, in addition to these public versions above, of course there are some other versions, as of 2015.1, the market share of each version is as follows:

After reading the above information, we may have such a question:
So many system versions, which version do we develop for?
This is what Android has to face as a "fragmentation" problem, and this problem is divided into two:
① System Fragmentation: We may need to do low-version compatibility when developing apps, such as minimum compatibility to version 2.3, and because of the popularity of various ROM customizations, people like to make some changes to the native system, which leads to problems that are feasible on native systems and not feasible on custom ROMs, such as camera calls ~
② Screen Fragmentation: The market on a variety of screen size mobile phones, 4.3-inch, 4.5-inch, 4.7-inch, 5.0-inch, 5.3-inch ... And so on, in addition to the mobile phone, there are Android tablet, so we may have to deal with the development of this screen adaptation problem, of course, just learn we do not need to consider these complex things, follow-up practical development we come to the bottom!

2.Android system features and platform architecture system features:

• Application Framework supports reuse and substitution of components (the app is published with the framework's conventions, and other apps can use the module)
• Dalvik virtual machines: optimized for mobile devices
  -Integrated Browser: Open source WebKit engine
• SQLite Structured data storage
• Optimized graphics library, multimedia support, GSM phone technology, Bluetooth, etc.
• Build with Software overlay method

Platform Architecture diagram:

A simple understanding of the architecture:

1. Application (Application layer)
   We generally say that the development of the application layer is carried out at this level, of course, including the system built-in a set of applications, using the Java language
2. Application Framework (Application framework layer)
   Regardless of the system built-in or our own written app, we need to use this layer, such as we want to call blacklist, automatically hang up the phone, we need to use the telephone management (Telephonymanager)
   With this layer we can easily implement the hang-up operation without needing to care about the underlying implementation
3. Libraries (Library) + Android runtime (Android runtime)
   Android gives us a library of C/s + + libraries for different components of the platform, such as the media framework, while the Android runtime is made up of the Android core library + Dalvik virtual machine, and the Dalvik virtual machine is a VM for mobile devices, and it features: It does not require fast CPU computation and a lot of memory space, and each app runs independently of each app in a separate Dalvik virtual machine for a Dalvik process, and his simple running process is as follows:
   
4. Linux kernel
   Here are the things that involve the underlying drivers, some system services such as security, memory management, and process management.

3. Summary of this section:

This section has an understanding of the history and status of Android, and then simply analyzes the Android system features and system architecture, these conceptual things that we know about, and the next section we'll start building Android environments!

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Android Basics Getting Started tutorial--1.1 background correlation and system architecture analysis