Android PlatformIntroduction

Hadipurnawan Satria, Ph.D

Source:Google Android PlatformZhahoui Wang, Angelous Stavrou, George Mason University

An Introduction to AndroidHuang Kuguang, Inha University

Android OS (CSE 2010)Xiao Ma

Internet users and Mobile phone users

Source: http://en.wikipedia.org/wiki/Digital_divide

Open Handset Alliance(OHA)

Mobile OperatorsHandset Manufacturers

Semiconductor Companies Software Companies Commercialization Companies

Source: http://www.openhandsetalliance.com

Android™ delivers a complete set of software for mobile devices: an operating system, middleware and key mobile applications.

Open

All application and Created equal

Breaking down application boundaries

Fast & easy application development

History of Android

• 2001 search service for wireless device

• 2005

– Acquire Android(Andy Rubin: Danger CEO, Development Sidekick of T-Mobile)

– Acquire Skia (2D Graphics for mobile device)

– Acquire RegWireless (Browser and Email for mobile device)

– Move Engineers from PlamSource (Dianne Hackborn, etc…)

• 2007 Nov 5: Android announced

• 2007 Nov 12: Android SDK released by OHA

• 2007 Dec 14: Bug-fix SDK released

• 2008 Jan 3: Android Developer Challenge I starts accepting submissions

• 2008 Feb 13: m5-rc15 SDK released

• 2008 Apr 14: 1788 total submissions for Challenge I

• 2008 May 12: Top 50 Applications in Challenge I announced

• 2008 Nov: Android Phone(G1 Phone by HTC/T-mobile)

• 2008 Nov: Full Source Open

• 2009 Apr: HTC Magic

• 2009 July: HTC Hero, Samsung i7500, Android Netbook, Set-top……

• 2009 Aug: Android Developer Challenge II

Industry Developer

Open

IndustrySoftware stack open-sourced under Apache 2.0 licenseSource available after first handsets shipAnyone will be able to build a system image

DeveloperDon not need permission to ship an applicationNo hidden or privileged framework APIsCan integrate, extendand replace existing components

UsersUsers have control of their experienceThey control what gets installedThey choose the defaults

Users

Integrate Extended Replace

Noteworthy Features Android uses Java:

• ... Everywhere, but only the mobile-appropriate bits!

• “Android is almost but not quite Java(tm)”

And so will you: • But nothing prevents native processes • Some native interfaces are available

Broad Java support: • java.io; • java.security;

• java.net; • java.sql;

Noteworthy Features Strong security: • Permissions-based • Applications sandboxed in separate VMs • Pervasive use of Linux process model Built-in SQL: • Property storage, retrieval • Utilized by nearly all standard components • Preferred, but not required Specialized APIs: • SurfaceFlinger • AudioFlinger

Noteworthy Features Highly-optimized Java implementation: • “Dalvik” VM implemented by Google • Custom bytecode format, processor model • Register-based, not stack-based Why? • “Didn’t want to pay Sun” (probably untrue) • Very memory- and performance-efficient • Highly tuned to limitations of small hardware Centralized object lifetime management: • Tied to component model • Tied to process model • Tied to user interface model • Tied to security model

Basic Terminology Activity : • A single visual user interface component • List of menu selections, icons, checkboxes, ... • A reusable component Service: • “Headless” activity component • Background processes Application: • Sequence of one or more Activities • Manifest tells which Activity to run first • Activities might come from other applications • Not the Linux concept of “application”!

Basic Terminology Task stack: • Sequences of application-centric Activity classes • Foreground is visible to user • BACK key returns to most-recent Activity Broadcast receiver : • Component that receives announcements • No user interface • May launch an Activity in response Content provider : • Provides application data to others • The only way to share data

Power Management Obviously important! • Can be a difficult problem to solve • Too much model exposure is bad • Too little is also bad Extends the Linux device model: • Introduces “wake locks” • See android.os.PowerManager In a nutshell: • Applications don’t control power at all • Applications hold “locks” on power states • If no locks are held, Android powers down

POWER SAVING

Picture is from Google I/O 09 talk - Coding for Life -- Battery Life, That Is

Audio and Video APIs MediaPlayer class: • Standard support for many data formats • URI invokes appropriate input method • Consistent API regardless of data source MediaRecorder class: • Support for audio recording only • Video recording is “planned” Surfaceflinger : • Centralized framebuffer management • Related to 2D h/w acceleration Audioflinger : • Centralized audio stream management You don’t work with these flingers directly!

Audio and Video APIs Example

1. MediaPlayer mp = new MediaPlayer(); 2. mp.setDataSource(PATH_TO_FILE); 3. mp.prepare(); 4. mp.start(); 5. mp.pause(); 6. mp.stop();

Android Architecture

Core LibrariesProvides the functionality of the JAVA Programming LanguageAndroid Application runs in its own process, with its own instance of the Dalvik virtual machineDalvik VM: Java based license free VM

•Register based VM, optimization for low memory requirements•Executes files in the Dalvik Executable (.dex) format•DX tool converts classes to .dex format

Details of Architecture(1/4)

Linux Version 2.6.x for core system servicesAndroid uses only “Kernel” portion in Linux

Details of Architecture(2/4)

• Libc: c standard lib.• SSL: Secure Socket Layer• SGL: 2D image engine• OpenGL|ES: 3D image engine• Media Framework: Core part of Android multi-media• SQLite: Embedded database• WebKit: Kernel of web browser• FreeType: Bitmap and Vector• Sufrace Manager: Manage difference windows for

different applications

Details of Architecture(3/4)

• No limited application• Equality of each apps.• Easy to embedded web browser• Parallel running

Details of Architecture(4/4)

• The Design goal of Android: Openness– Be as flexible as possible– How it handles access to

data: Mash up on the internet and everything else

– Rapid development(XML, Java)

• Develop Language– App: Java– Framework: Java– Libraries: C/C++– OS & Driver: C

Java

C/C++

C

The Hardware CPU: Qualcomm QSX8250 1Ghz

Mother board: Qualcomm Mobile Station Modem

(MSM) chipset , MSM7k series

RAM: 512 MB

ROM: 512 MB , partitioned as

boot/system/userdata/cache

External Storage: 4GB micro SD

Audio Processor: msm_qdsp6 onboard processor,

Firmware at /system/etc/vpimg

The Hardware Camera: Sensor_s5k3e2fx,5 MegaPixels Wifi+BlueTooth+FM: Boardcom BCM 4329,

802.11a/b/g/n, firmware at /system/etc/firmware/fw_bcm4329.bin

Touch Screen Input: msm_ts touchscreen controller, capella

Vibrator: Msm_vibrator on board vibrator Digital Compass: AK8973 More at

http://www.google.com/phone/static/en_US-nexusone_tech_specs.html

The Hardware

Application Architecture

• Dev. Language: Java• Virtual Machine:

– Dalvik VM, not JVM.– Open source

• Application: consists of one or more of the following classifications– Activities– Services– Content providers– Broadcast receivers

Dalvik Virtual Machine

APPLICATION LIBRARY

GNU libs (glibc) is too big and complicated for mobile phones, so Android implements its own special version of libc - Bionic libc:

Smaller size - 200K (glibc is more than 400K)

Strip out some complicated C++ features, the most significant one - no C++ exception!

Very special and small pthread implementation, heavily based on kernel futexes

Bionic libc does not fully support POSIX and is not compatible with glibc

which means ...?

PROCESS MANAGEMENT

What’s the difference between mobile apps cycle and desktop apps cycle?

Two key principles

Android usually do not kill an app, i.e. apps keep running even after you switch to other apps

Android kills apps when the memory usage goes too high, but it saves app state for quick restart later on

Do they make sense to mobile apps?

APPLICATION LIFE CYCLE

EXAMPLESystem

HomeHome

Home

At the “Home” screen

EXAMPLESystem

Home

Mail

Home

List

Home List

Start the “Mail” app and read the list

EXAMPLESystem

Home

Mail

Home

List Message

Home List Message

Click on one of the message and see its content

EXAMPLESystem

Home

Mail

Home

List Message

BrowserBrowser

Home List Message Browser

Click a link in the message

EXAMPLESystem

HomeHome

BrowserBrowser

Home List Message Browser

Now we have enough space to start the “Map” app

EXAMPLESystem

HomeHome

BrowserBrowser

Home List Message Browser

MapMap

Map

Start the “Map” app

EXAMPLESystem

HomeHome

BrowserBrowser

Home List Message Browser

Map

Go back to the browser

EXAMPLESystem

HomeHome

Browser

Home List Message

MailList Message

The “Mail” app is resumed and shows the previous message

EXAMPLESystem

HomeHome

Browser

Home List

MailList

Go back to the mail list

EXAMPLESystem

HomeHome

Browser

Home

Mail

Go back to the “Home” screen

DEBATE

Swapping modelVS.

Android’s life-cycle model

DISK I/O

Flash Hard Disk Drive

Random access ~0.1ms 5-10ms

File fragment impact No Greatly impacted

Total power 1/2 to 1/3 of HDD up to 15+ watts

Reliability Reliable Less reliable due to mechanical parts

Write longevity Limited number of writes Less of a problem

Capacity <= 512GB 2-3TB

Price $1.5-2 / GB $0.1-0.2 / GB

LIMITED WRITES?

Flash drives have the well-known problem of limited number of writes in the life time - 10,000~100,000 times. Solution?

What can applications do?

How about operating system?

Controllers?

Hardware?

MEMORY MANAGEMENT

Linux kernel does most of the job

Page-based memory management

Virtual address to physical address mapping

NO virtual memory

Why do we still need “virtual to physical” address mapping?

Why does Android not support virtual memory?

POWER MANAGEMENT

DALVIK VM

Why does Android let developers use Java?

DALVIK VM

A special Java virtual machine (VM) designed to run with limited system resource

Memory efficiency

Register machine vs. Stack machine (modern JVM)

fewer instructions, faster execution

why does the number of instructions matter?

Running multiple VMs more efficiently

DEX FILE

Java class files are converted into “.dex” files that Dalvik executes

Java byte-code is converted into Dalvik byte-code during this process

MEMORY EFFICIENCY

Shared constant string pool

Share clean (even some dirty) memory between processes as much as possible

“.dex” files are mapped as read-only by mmap()

Memory efficient JIT implementation

JIT itself is about 100K

Code cache and supporting data structure takes another 100K for each application

SHARED STRING POOLpublic interface Zapper { public String zap(String s, Object o);}

public class Blort implements Zapper { public String zap(String s, Object o) { .... }}

public class ZapUser { public void useZap(Zapper z) { z.zap(...); }}

SHARED STRING POOL

SHARED MEMORY

PROGRAMMING MODEL

Each application is running in its own process

An application can have one or more components:

activities, services, broadcast receivers and content providers

A task (an “application” from user’s point of view) consists of several activities from one or multiple applications

An application keeps running until the system kills it because of memory shortage

Android SDK

• android.jar Java archive file containing all of the Android SDK classes necessary to build your application.

• documention.html and docs directory The SDK documentation is provided locally and on the Web. It's largely in the form of JavaDocs, making it easy to navigate the many packages in the SDK. The documentation also includes a high-level Development Guide and links to the broader Android community.

• Samples directory The samples subdirectory contains full source code for a variety of applications, including Api Demo, which exercises many APIs. The sample application is a great place to explore when starting Android application development.

• Tools directory Contains all of the command-line tools to build Android applications. The most commonly employed and useful tool is the adb utility (Android Debug Bridge).

• Usb_driver Directory containing the necessary drivers to connect the development environment to an Android-enabled device, such as the G1 or the Android Dev 1 unlocked development phone. These files are only required for developers using the Windows platform.

Tools

• Emulator– Android applications may be

run on a real device or on the Android Emulator, which ships with the Android SDK.

• ADB (Android Debug Bridge)– The ADB utility lets you

connect to the phone itself and issue rudimentary shell commands, such as copying files to and from the device.

Development Environments

• Eclipse 3.2.3.3• Eclipse JDT Plugin• JDK 5 or 6• ADT：Android Development

Tools plug-in

Example: HelloWorldRunning on Emulator

Debugging your first Android App

Configure USB connection, if you are working with devices

Test adb and connect to device N:\android-sdk-windows\tools>adb devices * daemon not running. starting it now * * daemon started successfully * List of devices attached HT9CNP804091 device emulator-5556 device Launch a shell via adb: • The shell is actually on the target! N:\android-sdk-windows\tools>adb shell $

Debugging your first Android App

Summary

• Benefits– Open Platform/License Free– Robust OS Kernel, Innovative Library Packages– Ease App. Development– Rapid Improvement

• Challenges– Performance Consideration– Hard to Integrate for Vendors– Too Much Google Dependent

• Key Factor: Market Response