1. Android architecture overview
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2. Operating System (Linux Kernel 2.6)
Android
A software stack for mobile devices developed and managed by Open Handset Alliance
Free software under Apache License
Operating System (Linux Kernel 2.6)
Middleware
Key Applications
Android
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3. OHA (Open Handset Alliance)
A business alliance consisting of 47 companies to develop open standards for mobile devices
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4. Android Software Stack
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5. Android Software Stack– Linux Kernel
Relying on Linux Kernel 2.6 for core system services
Memory and Process Management
Network Stack
Driver Model
Security
Providing an abstraction layer between the hardware and the rest of the software stack
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6. Android Software Stack- Runtime
Core Libraries
Providing most of the functionality available in the core libraries of the Java language
APIs
Data Structures
Utilities
File Access
Network Access
Graphics
Etc
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7. Android Software Stack – Runtime (Cont)
Dalvik Virtual Machine
Providing environment on which every Android application runs
Each Android application runs in its own process, with its own instance of the Dalvik VM.
Dalvik has been written so that a device can run multiple VMs efficiently.
Register-based virtual machine
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8. Android Software Stack – Runtime (Cont)
Dalvik Virtual Machine (Cont)
Executing the Dalvik Executable (.dex) format
.dex format is optimized for minimal memory footprint.
Compilation
Relying on the Linux Kernel for:
Threading
Low-level memory management
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9. Android Software Stack - Libraries
Including a set of C/C++ libraries used by components of the Android system
Exposed to developers through the Android application framework
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10. Android Software Stack – App Framework
Enabling and simplifying the reuse of components
Developers have full access to the same framework APIs used by the core applications.
Users are allowed to replace components.
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11. Android Software Stack – App Framework (Cont)
Features
Feature
Role
View
System
Used to build an application, including lists, grids, text boxes, buttons, and embedded web browser
Content
Provider
Enabling applications to access data from other applications or to share their own data
Resource
Manager
Providing access to non-code resources (localized string, graphics, and layout files)
Notification Manager
Enabling all applications to display customer alerts in the
status bar
Activity
Managing the lifecycle of applications and providing
a common navigation backstack
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12. Android Software Stack - Application
Android provides a set of core applications:
Client
SMS Program
Calendar
Maps
Browser
Contacts
Etc.
All applications are written using the Java language.
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13. Reference
North Carolina State University: Android Real Time Systems,
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14. Your first Android app
Hello Android!
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15. Types of Android apps
Foreground: application that is effectively suspended when it is not visible
Background: spends most of its lifetime hidden
Intermittent: some interactivity, but most work done on background
Widget: home screen app
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16. Understanding: Hello Android
Activity: base class for visual, interactive components of your app
Code for activity
package org.example.helloAndroid;
import android.app.Activity;
import android.os.Bundle;
public class HelloAndroid extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState); }
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17. Understanding: Hello Android
View: visual components, visual interface
Code for activity
package org.example.helloAndroid;
import android.app.Activity;
import android.os.Bundle;
public class HelloAndroid extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main); }
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18. Understanding: Hello Android
Resources: stored in res
Drawable,
layout, and
values
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