Introduction to the basic aspects of application development in Android. The basic components, e.g., Activity and View, are introduced along with the different configuration files, e.g., AndroidManifest.xml.

1. Android components & manifest
Ilio Catallo, Eleonora Ciceri – Politecnico di Milano
ilio.catallo@polimi.it, eleonora.ciceri@polimi.it

2. Principles
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3. Android applications
¤ An Android application is made of different components
¤ Namely:
¤ Activities (and associated Views)
¤ Broadcast receivers
¤ Services
¤ Persistence Providers
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4. Android applications
¤ An Android application is made of different components
¤ Namely:
¤ Activities (and associated Views)
¤ Broadcast receivers
¤ Services
¤ Persistence Providers
4

5. Principles
5
activity
application
¤ An activity is a single, focused thing that the user
can do
¤ Each activity is associated with a window in which to
draw the user interface

6. Principles
6
view
activity
application
¤ The view is the basic building block for user
interface components
¤ Responsible for drawing and event handling
¤ Examples: button, textbox

7. Principles
7
view
activity
application
activity
view
¤ Most basic applications are made of just one Activity
¤ However, typical Android apps comprise multiple
Activities

8. Principles
8
intent
view
activity
application
activity
view
¤ Intents are messages that are passed between
components (e.g., Activities)
¤ The most significant use of Intents is launching new
Activities

9. Principles
9
intent
view
activity
application
activity
view
9
view
activity
third-party
application
¤ What if a useful Activity is part of
a third-party application?

10. Principles
10
intent
view
activity
application
view
activity
third-party
application
activity
view intent
¤ By casting an intent, third-party
activities can be used as if they
were part of our app

11. Remaining components
¤ The remaining components play less intuitive roles
¤ Namely:
¤ Services implement long-running, background operations
¤ Persistence providers supply access to data managed by
the application
¤ Broadcast receivers enable applications to receive intents
that are broadcast by the system or by other applications
11

12. Composing the puzzle
12

13. Composing the puzzle
¤ Each Android application includes a manifest file
(AndroidManifest.xml), which describes
¤ each single component
¤ the interaction between different components
¤ Specifically, the manifest defines:
¤ the application metadata
¤ the application requirements
¤ the application structure and components
¤ The manifest is stored in the root of the project hierarchy
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14. Manifest structure: manifest node
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uses-sdk
application
activity
service
provider
receiver
intent-filter
¤ <manifest> is the root node of the
AndroidManifest.xmlfile
<manifest
xmlns:android=
“http://schemas.android.com/apk/res/android”
package="it.polimi.mad”
android:versionCode="1"
android:versionName="0.9 Beta"
android:installLocation="preferExternal”>
...
</manifest>

15. Manifest structure: manifest node
15
uses-sdk
application
activity
service
provider
receiver
intent-filter
¤ Attributes
¤ versionCode: an integer
representing the version of the
application code
¤ versionName: a string
representing the release version
of the application code, as
shown to users
¤ installLocation: the default
install location for the application

16. Manifest structure: uses-sdk node
16
uses-sdk
application
activity
service
provider
receiver
intent-filter
¤ <uses-sdk> lets you express an
application’s compatibility with one
or more versions of the Android
platform
¤ This tag specifies the version of the
APIs, NOT the SDK
<uses-sdk android:minSdkVersion=“8”
android:targetSdkVersion=”21” />

17. Manifest structure: uses-sdk node
17
uses-sdk
application
activity
service
provider
receiver
intent-filter
¤ Attributes
¤ android:minSdkVersion: an
integer designating the minimum
API Level required for the
application to run
¤ android:targetSdkVersion: an
integer designating the API Level
the application targets

18. Manifest structure: application node
18
uses-sdk
application
activity
service
provider
receiver
intent-filter
¤ <application> defines the
application metadata
¤ Example: icon, title
¤ It acts as a container for activities,
services, content providers and
broadcast receivers
<application android:icon="@drawable/icon”
android:name= ”.MyApp"
android:debuggable="true">
...
</application>

19. Manifest structure: application node
19
uses-sdk
application
activity
service
provider
receiver
intent-filter
¤ <application> defines the
application metadata
¤ Example: icon, title
¤ It acts as a container for activities,
services, content providers and
broadcast receivers
<application android:icon="@drawable/icon”
android:name= ”.MyApp"
android:debuggable="true">
...
</application>
. is used as a shorthand
for the application’s
package name

20. Manifest structure: application node
20
uses-sdk
application
activity
service
provider
receiver
intent-filter
¤ Attributes
¤ android:icon: reference to a
resource containing the
application icon image
¤ android:name: the fully qualified
name for the class inheriting from
Application*
* The subclass is optional. In the absence of a subclass, an
instance of the base Applicationclass is used

21. Manifest structure: activity node
21
uses-sdk
application
activity
service
provider
receiver
intent-filter
¤ <activity> is required for every
Activity within the application
<activity android:name=".MyActivity”
android:label="@string/activity_name">
...
</activity>

22. Manifest structure: activity node
¤ Attributes
¤ android:name: the name of the
class that implements the activity
(should be a fully qualified class
name)
¤ android:label: a user-readable
label for the activity, displayed
when the activity is represented
to the user (often along with the
activity icon)
22
uses-sdk
application
activity
service
provider
receiver
intent-filter

23. Manifest structure: intent-filter node
23
uses-sdk
application
activity
service
provider
receiver
intent-filter
¤ <intent-filter>specifies the
types of intents that an activity,
service, or broadcast receiver can
respond to
<intent-filter>
<action android:name="android.
intent.action.MAIN”/>
<category android:name="android.
intent.category.LAUNCHER”/>
</intent-filter>

24. Manifest structure: intent-filter node
24
uses-sdk
application
activity
service
provider
receiver
intent-filter
¤ Sub-nodes
¤ action: the name of the action
¤ category: adds a category name
to an intent filter.
¤ Some standard actions and
categories are defined in the Intent
class
¤ ACTION_MAIN: starts up as the initial
activity of a task (no data input
and no returned output)
¤ CATEGORY_LAUNCHER: the activity
must be invoked by the launcher

25. Manifest structure: service node
25
uses-sdk
application
activity
service
provider
receiver
intent-filter
¤ <service> declares a Service
class implementing long-running
background operations
<service android:name=".MyService">
...
</service>

26. Manifest structure: service node
26
uses-sdk
application
activity
service
provider
receiver
intent-filter
¤ Attributes
¤ android:name: qualifiedname
of the class implementing the
service

27. Manifest structure: provider node
27
uses-sdk
application
activity
service
provider
receiver
intent-filter
¤ <provider> declares a content
provider component, supplying
access to data managed by the
application
<provider android:name=".MyContentProvider"
android:authorities=“it.polimi.
mad.contentprovider"/>

28. Manifest structure: provider node
28
uses-sdk
application
activity
service
provider
receiver
intent-filter
¤ Attributes
¤ android:name: the fully qualified
name of the class that
implements the content provider
¤ android:authorities: a list of
one or more URIs that identify
data offered by the content
provider
¤ To avoid conflicts with
content providers in other
apps, the URIs should use a
Java-style package naming
convention

29. Manifest structure: receiver node
29
uses-sdk
application
activity
service
provider
receiver
intent-filter
¤ <receiver> declares a broadcast
receiver as one of the application's
components
¤ Broadcast receivers enable
applications to receive intents
that are broadcast by the system
or by other applications
<receiver android:name=".MyIntentReceiver">
<intent-filter>
<action android:name=”it.polimi.
mad.mybroadcastaction”/>
</intent-filter>
</receiver>

30. Manifest structure: receiver node
30
uses-sdk
application
activity
service
provider
receiver
intent-filter
¤ Attributes
¤ android:name: the fully qualified
name of the class that
implements the broadcast
receiver

31. TakeNotes:
AndroidManifest.xml
31
Android 5.0
(Lollipop)
Android 2.2
(Froyo)
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="it.polimi.ma.takenotes"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk android:minSdkVersion="8"
android:targetSdkVersion="21" />
<application android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name" >
<activity
android:name="it.polimi.ma.takenotes.ToDoListActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>

32. TakeNotes:
AndroidManifest.xml
32
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="it.polimi.ma.takenotes"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk android:minSdkVersion="8"
android:targetSdkVersion="21" />
<application android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name" >
<activity
android:name="it.polimi.ma.takenotes.ToDoListActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
One single activity,
implemented by this class

33. TakeNotes:
AndroidManifest.xml
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="it.polimi.ma.takenotes"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk android:minSdkVersion="8"
android:targetSdkVersion="21" />
<application android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name" >
<activity
android:name="it.polimi.ma.takenotes.ToDoListActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
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Resource URI
(we will see in a while
what it means…)

34. Android application structure
¤ Programming an Android application involves:
¤ Writing the business logic code
¤ Providing the resources required for the user interface
¤ User interface definition (via XML)
¤ Icons
¤ Localized strings
¤ Providing the multimedia content (i.e., assets), which will be
used by the application
¤ Video / photo collections
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35. Android Project File Structure
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src/
build/
Source code that is auto-generated by Android Studio
libs/
Precompiled third-party libraries (JAR archives) that you
want to use in your app
assets/
Other media that you want to use in your app (e.g.,
videos, sounds)
res/
GUI layouts, icons, menus and so forth
java/
Source code that you write for your app
main/
source code and resources
app/

36. Create a Hello World application
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37. Hello World application – Step 1
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Specify the application name...
... and the company name (which automatically
defines the package name)

38. Hello World application – Step 2
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Specify the platform on which the application will run...
... and the supported API

39. Hello World application – Step 3
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Select this to create a
standard, empty activity

40. Hello World application – Step 4
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Give a name to the activity (i.e., the
Java class implementing the activity)

41. Android Studio:
Hello World application
41
Project structure
Code
Application
preview

42. References
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43. References
¤ Reto Meier, Professional Android 4 Application
development
3rd Ed., Wrox
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