Android Middleware

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Android Middleware

Bo Pang

[email protected]

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Android System Architecture

Source: Google

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overview

Linux Kernel: memory management, process

management, networking, and other

operating system services.

Native Libraries: written in C or C++, including:

Surface Manager, 2D and 3D graphics, Media

codes, SQL database, Browser engine, etc.

only to be called by higher level programs

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overview

Android Runtime: including the Dalvik virtual

machine and the core Java libraries. (not

J2SE/J2ME)

Application Framework: Activity manager,

Content providers, Resource manager,

Notification manager

Applications and Widgets: the real programs

display information and interact with users.

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Media Framework

Android use OpenCore as core component of

Media framework

OpenCore supports MP3, AAC, AAC+, 3GPP,

MPEG-4 and JPEG,

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Media Framework

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Media Framework

Example:

MediaPlayer mp = new MediaPlayer();

mp.setDataSource(PATH_TO_FILE); mp.prepare();

mp.start();

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Media Framework

OpenCore lib has a C/S Architecture.

MediaPlayer invoke JNI to manipulate client.

The client request to the server to controlhardwares.

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Media Framework

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Media Framework

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Activity Manager

each user interface screen is represented by

an Activity class.

Each activity has its own life cycle.

Activity uses Intent object to jump between

them.

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Life cycle of activity

Source: Hello

Adroid

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Intent and Intent filters

Intent activates activities, services, and

broadcast receivers.

Intent can be used in explicit way or implicit

way.

The implicit way depends on parameters:

Action, Data(url and MIME type) , Category

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Intent and Intent filters

To receive other components' request,

components need to register filters at

activities framework.

When launch a intent object, framework will

match and find the qualified components and

leave them for users to choose which to run.

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Intent and Intent filters

Example

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Activities and Tasks

A task is a stack which contain several

activities share the same affinity.

Source:

http://blog.akquinet.de/20

10/02/17/android-activities-the-

predominance-of-the-ui-

thread/

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Activities and Tasks

There are four different launch modes thatcan be assigned to an element'slaunchModeattribute:

"standard" (the default mode)"singleTop""singleTask""singleInstance"

First two share the same affinity withapplication, the others dont.

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Content manager

Manage data

Client+server architecture.

Content Resolver provides API interface forapplications.

Content Providers is the server managing the

DB tables and database content with different

application.

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Content manager

URI identifies the data or the table

A: Standard prefix indicating that the data is

controlled by a content provider.

B: The authority part of the URI; it identifies the

content provider.

C: The path that the content provider uses to

determine what kind of data is being requested.

D: The ID of the specific record being requested.

Source: Google

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Service Lifecycle

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Security and permissions

security between applications and the system

is enforced at the process level through

standard Linux facilities

Application can't disrupt other applications,

except by explicitly declaring the permissions

it

Each Android package is given its own unique

Linux user ID

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References

http://www.j2medev.com/android/ShowArticl

e.asp?ArticleID=5439

http://docs.huihoo.com/google/io/2009/Mast

ering_the_Android_Media_Framework.pdf

http://developer.android.com/