Overview of Android (Part 3): Application Framework & Apps ... · 13 • An app registers...

Overview of Android (Part 3):

Application Framework & Apps Layers

Douglas C. Schmidt

d.schmidt@vanderbilt.edu

www.dre.vanderbilt.edu/~schmidt

Professor of Computer Science

Institute for Software

Integrated Systems

Vanderbilt University

Nashville, Tennessee, USA

Learning Objectives in this Part of the Lesson1. Understand what is an

application framework & know why it’s useful

2. Recognize common system services in the AndroidApplication Framework layer

ART|Dalvik Virtual Machine

2. Recognize common system services in the AndroidApplication Framework layer

3. Recognize common apps that are available on an Android device

Overview of Application Frameworks

See www.dre.vanderbilt.edu/~schmidt/frameworks.html

• A framework is an integrated set of components that provide a reusable architecture for a family of related apps

• Frameworks use an event-driven programming model to plug app code into them

Register for event

Eventoccurs

See en.wikipedia.org/wiki/Event-driven_programming

ApplicationCode

FrameworkCode

• Frameworks use an event-driven programming model to plug app code into them

• They enhance systematic reuse by providing canonical structure & functionality to apps

Register for event

Eventoccurs

ApplicationCode

FrameworkCode

See en.wikipedia.org/wiki/Code_reuse#Systematic_software_reuse

• An app registers callbacks for specific types of events that can occur within the framework

Register for event

ApplicationCode

FrameworkCode

Eventoccurs

See en.wikipedia.org/wiki/Callback_(computer_programming)

• A callback is an object passed as an argument to a framework

Register for event

ApplicationCode

FrameworkCode

Eventoccurs

• The framework monitors event sources for activity of interest

Register for event

Eventoccurs

ApplicationCode

FrameworkCode

e.g., arrival of network messages, clicks on

GUI components, etc.

• Framework calls back the object when an event of interest occurs

Register for event

Eventoccurs

ApplicationCode

FrameworkCode

• Framework calls back the object when an event of interest occurs

• The app processing occurs in context of framework thread(s)

Register for event

Eventoccurs

ApplicationCode

FrameworkCode

• When app callback is done control returns to the framework, where it waits for the next event to occur

Register for event

Eventoccurs

ApplicationCode

FrameworkCode

• When app callback is done control returns to the framework, where it waits for the next event to occur

• Lather, rinse, repeat until app is done …

Register for event

Eventoccurs

ApplicationCode

FrameworkCode

See en.wikipedia.org/wiki/Lather,_rinse,_repeat

Overview of the Android Application Framework

& Apps Layers

• The Application framework layer contains system servicesthat provide apps with the capabilities & info they need to do their work

See opensourceforu.efytimes.com/2013/12/birds-eye-view-android-system-services

Overview of Android: Application Framework & Apps Layers

• Expose hardware & Linux OS kernel capabilities to apps

• Run continuously during system operation

• Control flow is driven by various events & callbacks

21These system services are largely written in Java, with some C/C++ native code

22This service uses intents to interact with activities, services, & broadcast receivers

We focus on the Activity Manager Service

throughout this course

• Atop Android’s software stack are apps used every day

See android.googlesource.com/platform/packages/apps

• The bulk of these appsare written in Java

• It’s also possible to writeapps in C/C++

See developer.android.com/ndk

• It’s also possible to writeapps in C/C++

• As well as Kotlin!

See developer.android.com/kotlin

End of the Overview of Android (Part 3): Application

Framework & Apps

Overview of Android (Part 3): Application Framework & Apps ... · 13 • An app registers...

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