This document provides an overview of basic Android application components and concepts, including Activities, Context, Intents, Services, Broadcasts, BroadcastReceivers, and Storage options. It discusses what each component is used for and provides examples. It also describes a code demo that records and shares battery levels over time using some of these components and concepts.

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Today’s Manifest
● An app has several interfaces to interact with
the Android system.
● Basic building blocks we’d discuss
o Activity
o Context
o Intent
o Service
o Broadcast and BroadcastReceiver
o Storage

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Activity
● Application component which interacts with
the user
● Interaction happens via the Android UI
o i.e. the screen
● An app usually starts with a default Activity
● It can ask Android to start new Activities
http://developer.android.com/guide/components/activities.html

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Context
● The interface to the environment of the
application.
● Allows access to resources
o R’s resources, System resources (e.g. Content
providers)
● Allows calling new activities
o new Activities, Services
● Brings in new requests
o Broadcasts

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Intent
● A messaging object which can be used to
request action from another application
component
● Can be used to
o Start Activity
o Start Service
o Deliver a broadcast

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Intent
● Two types
o Explicit
o Implicit
● Contains >>
Intent
Component Name
Action
Data
Category
Extras
Flags

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Explicit Intent
● Specifies which component to use / start
o Starting new Activity in the app
o Starting new Service
Intent mainShowIntent =
new Intent(
getApplicationContext(),
ScreenMain.class);
startActivity(mainShowIntent);

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Implicit Intent
● Declares a general action
to perform
o Send SMS, email
o Share something
● When the intent is
delivered to Android
System, it either decides
which app to use, or asks
the user if there are
multiple

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Service
● Application component which runs in the
background
● Continues to run even if the user switches to
another app.
● Can be started from an Activity using an
Intent
What do you
mean what are
they?
I just told you!

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Broadcast
● System-wide message sent to apps
● Broadcast contains an Intent and a Context
it was fired.
● Two types
o Un-Ordered (Normal)
o Ordered

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Broadcast Receiver
● Listens to a broadcast
● The broadcast can be triggered by the
system, another app and the same app.
● Application can opt-in to listen using an
Intent Filter specified in;
o Manifest entry
o By creating a runtime object

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Storage
● Google lists the following storage options
o Internal Storage
o External Storage
o Shared Preferences
o Database
o Network

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Storage - Internal Storage
● Private to the application
● Read / Write as a File
● Stored in a safe app-limited location
● Deleted when the app is uninstalled

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Storage - External Storage
● Stores data on the external disk
● Can be SD card / USB
● Use with care. The user could
o Un-mount the volume
o Connect the card to a PC
Which would make this unavailable for
app’s usage

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Storage - Shared Preferences
● App-limited data space
● Uses key-value pairs
● Only primitive data types can be stored
● Great for small persistent values in app
Note: Settings has a separate set of functions to make
things easy. Don’t manually store user’s preferences

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Storage - Database
● Android comes with a sqlite database
● Apps have their own databases
● Simple queries can be executed

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Storage - Network
● Use the internet / Wifi to send data to a
server
● How? Anyway you like
o JSON
o XML
o HTTP GET, POST
o or whatever method you want… just decide…

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Code Demo
Simple app to:
● Record the battery level every 10s
● View the current level
● View recorded values
● Share recorded values

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Stage 1
● Setup the Main Activity
● Setup the Service
o Code the required startup and looping in the service
o Code the broadcast to send
● Start the service from the activity
● Register for broadcasts from the service
● See the initial results

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Stage 2
● Setup a BroadcastReceiver and add it in the
manifest
● Use that class to record the samples
● Create an additional Activity to view samples

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Stage 3
● Configure a share menu item
● Share using intents

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Finalized Code
Code is available at
https://github.com/tdevinda/DialogAndroidIntro_2.git

24. Thanks for your participation!