Android Basic Concept Understanding

Android's Past Life
Android System Framework
Android Main components
Common Android Operations

Android's Past Life

• The birth of Android
  In October 2003, Andy Rubin, the "Father of Android", founded Android Inc. (Android Inc) in Palo Alto, California, USA. Andy Rubin.

• Android's history
  Google (Google) acquired the company on August 17, 2005 and has been developing it into its current Android system.
  November 12, 2007, the Android Beta operating system SDK is officially released.
  Released September 23, 2008, this is also the earliest version of the Android system. Android 1.0
  With the release of 1.0, the first Android phone to be powered by Android 1.0 OS was born. Because 1.0 does not support touch input, the G1 is configured with a physical keyboard. Image of HTC Dream (G1)
  
  Released April 30, 2009. From then on, the Android version was named after the pastry and sorted alphabetically.
  
  Released September 15, 2009. ANDROID1.6 supports CDMA networks for the first time, Android 1.6
  
  November 2009 Android 2.0
  
  Released May 20, 2010. It seemed that Google had only begun to seriously consider Android's enterprise features until Android2.2 was released.
  
  Released December 7, 2010. This version starts with NFC support, Android 2.3
  
  Released February 2, 2011. "Hive" Android 3.0, designed for flat panel design
  
  Released October 19, 2011 in Hong Kong. Android4.0
  
  Released June 28, 2012. Android4.1 is Google after the hive, a new tablet strategy attempt.
  

Released October 15, 2014, Lollipop (Lollipop): Android 5.0

New material Design Style
Support for multiple devices
Support for 64-bit art virtual machines

September 30, 2015, Marshmallow (cotton Candy): Android 6.0

Native app Rights Management
Supports RAW format photos
Support for fast Charge switching

May 18, 2016, Nougat (nougat): Android N (Android 7.0)

Split-screen multi-tasking
New pull-down shortcut switch page
System-Level phone blacklist function
Night mode
Notification message Quick Reply

• Future direction of Android development forecast
  Smartphones are bound to become smarter, but Android is a phalanx of smartphones, and naturally has its life cycle.
  Now, Android is at its zenith, and it is unlikely to be replaced by anything other than a product that is not enough to replace the smartphone.
  Android has now joined the smart home configuration, which will also enhance authentication on identity, integrating a wide variety of ID Card.
  Now Android is not just a mobile phone, in the car navigation, in the television, where there is a screen, there may be its site.

Android System Framework

• Basic cognition
  From the user's point of view, the first time to get an Android phone, it is obvious that the Windows desktop is somewhat similar to the installation of some applications on the basis of the system.
  The intuitive understanding is that Android is divided into the system layer and the application layer.
  Android also has a lot of hardware devices that the computer does not have, these are all have its own driver to boot.
  People who have a certain system knowledge know that the system can be divided into kernel layer, system running library, interface and so on several levels.
  But these are all relatively simple cognition, below or from its actual frame to understand the level of Android
• Frame diagram
  
  As you can see, Android is mainly divided into four levels
  Linux kernel layer
  System Runtime Library Android Run-time library
  Application Framework Layer
  Application Layer
  The application layer is best understood and is an important part of the value of smart phones.
  The application architecture layer, which is also the most commonly used part of the programmer, includes the four most famous Android components
  System runtime, the program to use some common Couroux (database, font library, browser engine, graphics, media Library, etc.)
  The Linux kernel is something that drives, file systems, security, networks, and so on, that deal almost directly with hardware.

Android Main components

• Four components
  activity
  Direct translation: activities, that is, you can see the interface of the object, should be considered activity.
  It is implemented by fragment or View (control) padding. A form interface similar to computer software.
  The mouse click event of the form interface, in activity, is the click event of the finger, but the finger can do more, that is, the activity can respond to a variety of operations. (Point, long Press, double-click, drag, etc.)
  each activity has its own life cycle, and like people, there are times when they are born, when they are used, when there is a pause (sickness), when there is recovery, and of course there is death and destruction (cremation). In different times, activity corresponds to do the corresponding things, such as: birth is just to create a new life, it can not do anything, grow up to be able to deal with some things. The
  contentprovider
  Content provider, which is the equivalent of a cloud space, can get the content in it or put it in the cloud.
  This allows you to save a lot of space without having to build a database on your own, while eliminating the fact that the same type of data cannot be found in different software. The
  broadcastreceiver
  Broadcast, which is the speaker of the phone, can be placed outside the voice, can also be heard with the ear. The
  out-of-band voice is anyone can hear, who can handle (of course, there are some special places)
  with the ears to listen, you can only hear themselves, send themselves to broadcast, their own broadcast, their own processing. What is the benefit of the
  ? When there is news, do not have a notice, who to deal with, who deal with go.
  If it's my own news, you can order it, and I'll deal with it naturally.
  Service
  Services, which are code that runs in the background, are not displayed in the interface.
  There was a doubt that the songs running in the background didn't have a notification bar display? In fact, that is just the notification bar interface, and service does not matter, not the interface can also play songs. The
  service is a bit like a human brain, you can't see it's counting things, but it can design things in the brain, do all kinds of complex calculations, and you can dream all night.
  But the brain is not for no reason to start the operation, but to have a certain trigger conditions, such as seeing something, what happened, and so on, the service is the same, must be a thing to trigger it to start, and tell the program when I finished, and then return a result.

• Mobile phone hardware (sensor)
  Now the mobile phone is getting stronger, but the change is mainly on the hardware, the software change is not much.
  Hardware changes are mainly: the various sensors of the addition, such as the most famous (camera!! ）
  NFC, Bluetooth, fingerprint, temperature sensor, etc.
  With the addition of these things, mobile phones are becoming more and more powerful, which may make it difficult for many traditional computers to realize their abilities.
  Also brings a lot of interesting ideas for software design.

Common Android Operations

Now the smartphone, with fewer keyboards, because the ability to manipulate the finger more than the keyboard is much stronger, mobile phone can point, press, double-click, drag, two strokes, drawing, fingerprints, and so on.
Thanks to the infinite flexibility of the fingers, Android also has a variety of feedback capabilities.
such as: Press, lift, move, you can assign it a reaction action.

From for notes (Wiz)

Android Basic Concept Understanding