The document discusses intents in Android and how they allow communication between application components. Intents are objects that specify operations or events and contain action, data, category and other metadata. They allow activities to start other activities both within and between apps to perform tasks like taking a photo, making a call, or opening maps. When an activity starts another activity via an intent without specifying the component, Android performs intent resolution to match the intent to a capable activity based on intent filters.

1. Todays topics
• The Intent Class
• Starting Activities with Intents
• Explicit Activation
• Implicit Activation via Intent resolution

2. The Intent Class
• a data structure that represents
1. An operation to be performed, or
2. An event that has occurred

3. Using Intents to perform Certain Operations
• Intents used to start a single activity
• Intents provide a flexible language for specifying operations to be performed
• Pick a contact
• take a photo
• Dial a phone number
• Open a web-browser
• Open a google map
Android application components can
connect to other Android applications. This
connection is based on a task description
represented by an Intent object
Intents allow you to interact with components from the same
applications as well as with components contributed by other
applications.
For example, an activity can start an external activity for taking
a picture.

5. In Android the reuse of other application components is a concept known as task. An
application can access other Android components to achieve a task. For example, from a
component of your application you can trigger another component in the Android system,
which manages photos, even if this component is not part of your application
1. Intent is constructed by
one component that
wants some work done
2. Received by one activity
that can perform that
work

7. • String representing desired operation
Action
Data
Category
Type
Component
Extras
Flags

8. Action
• String representing desired operation
ACTION_DIAL – Dial a number
ACTION_EDIT – Display data to edit
ACTION_SYNC – Synchronize device data with server
ACTION_MAIN – Start as initial activity of app
ACTION_VIEW: Display the data to the user.
Code
Intent newInt = new Intent();
newInt.setAction(Intent.ACTION_DIAL);

9. Data
• Data associated with the Intent
• Formatted as a Uniform Resource
Identifier (URI)
• Data to view on a map
• Uri.parse(“geo:0,0?q=1600+Pennsyl
vania+Ave+Washington+DC”)
• Number to dial in the phone dialer
• Uri.parse(“tel:+15555555555”)

10. Data
• Add’l information associated with
Intent
• Treated as a map (key-value pairs)

11. Category
• Additional information about the components that can handle the
intent
• Examples
• Category_browsable – can be invoked by a browser to display data
ref’s by a URI
• Category_launcher – can be the initial activity of a task & is listed
in top-level app launcher

12. Type
• Specifies the MIME type of the Intent data
• examples
• image/*, image/png, image/jpeg , text/html, text/plain
• If unspecified, Android will infer the type

13. Component
• The component that should
receive this intent
• Use this when there’s exactly
one component that should
receive the intent

14. Starting Activities for Intents
startActivity(Intent
intent,…)
startActivityForResult(Intent
intent, …)

15. Target Activity
• Can be named explicitly by setting the intent’s component
• Can be determined implicitly

16. Intent Resolution
• When the Activity to be
activated is not explicitly
named, Android tries to find
Activities that match the
Intent
• This process is called intent
resolution

17. Intent Resolution
•An Intent describing a desired operation
•Intent Filters which describe which
operations an Activity can handle Specified
either in AndroidManifest.xml or
programmatically

18. Intent Resolution Data
Action
Data (both URI & TYPE)
Category

20. Action
Category
Type
Note: to receive implicit
intents an Activity
should specify an
IntentFilter with the
category
"android.intent.category.
DEFAULT”

21. Further Syntax