1. Android Mobile Application Development
Intents and Filters
Lecture Four
Assistant Lecturer
Mustafa Ghanem Saeed
Computer science Department
Collage Of Science
Cihan University - Sulaimaniyah

2. What are intents?
Intents are asynchronous messages which allow application components to request functionality from other Android components. 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.
Intents are objects of the android.content.Intent type.
Your code can send them to the Android system defining the components you are targeting.
For example, via the startActivity() method you can define that the intent should be used to start an activity.

3. Android intents are mainly used to: (Question)
Open another Activity or Service from the current Activity
Pass data between Activities and Services
Give responsibility to another application. For example, you can use Intents to open the browser application to display a URL.
Broadcast a message.
Dial a phone call etc.

4. Types of Android Intents (Question)
Implicit Intent
Implicit Intent specify the action which should be performed and optionally data which provides content for the action.
For example, the following tells the Android system to view a webpage. All installed web browsers should be registered to the corresponding intent data via an intent filter.

5. Types of Android Intents (Question) cont.
2- Explicit intents explicitly define the component which should be called by the Android system, by using the Java class as identifier.
The following code demonstrates how you can start another activity via an intent.

6. Types of Android Intents (Question) cont.
use explicit intents to:
start a new activity
start an activity to get a result
start a service
broadcast an intent
start a new activity from within a broadcast receiver
use implicit intents to:
use other app’s components to:
send an
pick a contact from the contacts list
make a phone call
use a pending intent to send a notification

7. Intent Filters There are following Five elements in an intent filter:
Action
It represent an activities action, what an activity is going to do.
Data
There are two forms in which you can pass the data, using URI(Uniform Resource Identifiers) or MIME type of data
Category
This attribute of Intent filter dictates the behavior or nature of an Intent
Extras
Key-value pairs for additional information that should be delivered to the component handling the intent
Flags
These flags are optional part of Intent object and instruct the Android system how to launch an activity, and how to treat it after it's launched etc.
Important Note: Every intent filter must contain action element in it. Data and category element is optional for it.

8. Intent Filters-Action 1
The Intent class defines a number of action constants, including these:
Constant
Target component
Action
ACTION_CALL
activity
Initiate a phone call.
ACTION_EDIT
Display data for the user to edit.
ACTION_MAIN
Start up as the initial activity of a task, with no data input and no returned output.
ACTION_SYNC
Synchronize data on a server with data on the mobile device.
The action largely determines how the rest of the intent is structured — particularly the data and extras fields — much as a method name determines a set of arguments and a return value. For this reason, it's a good idea to use action names that are as specific as possible, and to couple them tightly to the other fields of the intent. In other words, instead of defining an action in isolation, define an entire protocol for the Intent objects your components can handle.
The action in an Intent object is set by the setAction() method and read by getAction().

9. Intent Filters-Action 2
The Intent class defines a number of action constants, including these:
Constant
Target component
Action
ACTION_BATTERY_LOW
Broadcast Receiver
A warning that the battery is low.
ACTION_HEADSET_PLUG
A headset has been plugged into the device, or unplugged from it.
ACTION_SCREEN_ON
The screen has been turned on.
ACTION_TIMEZONE_CHANGED
The setting for the time zone has changed.

10. Intent Filters- Data
The URI of the data to be acted on and the MIME type of that data. Different actions are paired with different kinds of data specifications.
The URI: At the highest level a URI reference (Uniform Resource Identifiers) in string form has the syntax
[scheme:]scheme-specific-part[#fragment]
For example:
Short for Multipurpose Internet Mail Extensions, a specification for formatting non-ASCII messages so that they can be sent over the Internet. For Examples:
For Text "text/plain"
For Image :"image/jpeg“ , "image/bmp“ ,"image/gif“ , "image/jpg“ ,"image/png"
For Video: "video/wav“, "video/mp4"
news:comp.lang.java
For Text
"text/plain"
For Image
"image/jpeg"
"image/bmp"
"image/gif"
"image/jpg"
"image/png"
For Video
"video/wav"
"video/mp4"

11. Action/Data Pair & Description
Intent Filters- Data 2
Some examples of Action/Data Pair
Sr.No.
Action/Data Pair & Description 1
ACTION_VIEW content://contacts/people/1
Display information about the person whose identifier is "1". 2
ACTION_DIAL content://contacts/people/1
Display the phone dialer with the person filled in. 3
ACTION_VIEW tel:123
Display the phone dialer with the given number filled in. 4
ACTION_DIAL tel:123 5
ACTION_EDIT content://contacts/people/1
Edit information about the person whose identifier is "1".
For Text
"text/plain"
For Image
"image/jpeg"
"image/bmp"
"image/gif"
"image/jpg"
"image/png"
For Video
"video/wav"
"video/mp4"
<intent-filter >
<data android:type="video/mpeg" android:scheme="http" />
<data android:type="audio/mpeg" android:scheme="http" />
. . .
</intent-filter>

12. Intent Filters- Category
The Intent class defines several category constants, including these (More than 29 category):
Constant
Meaning
CATEGORY_BROWSABLE
The target activity can be safely invoked by the browser to display data referenced by a link — for example, an image or an message.
CATEGORY_DEFAULT
Set if the activity should be an option for the default action (center press) to perform on a piece of data.
CATEGORY_APP_MAPS
Used with ACTION_MAIN to launch the maps application.
CATEGORY_LAUNCHER
an activity on the top of stack, whenever application will start, the activity containing this category will be opened first..

13. Intent Filters- Extras
This will be in KEY-VALUE PAIRS for additional information that should be delivered to the component handling the intent. The extras can be set and read using the putExtras() and getExtras() methods respectively (More than 26 Extras):
For examples :
EXTRA_ A String[] holding addresses that should be delivered to.
EXTRA_HTML_TEXT: A constant String that is associated with the Intent, used with ACTION_SEND to supply an alternative to EXTRA_TEXT as HTML formatted text.
Intent i=new Intent(context,SendMessage.class);
i.putExtra("id", user.getUserAccountId()+"");
i.putExtra("name", user.getUserFullName());
context.startActivity(i);

14. Intent Filters- Flags 1
Flags defined in the Intent class that function as metadata for the intent. The flags may instruct the Android system how to launch an activity and how to treat it after it’s launched. (More than 33 Flags):
FLAG_ACTIVITY_CLEAR_TASK - Clear any existing tasks on this stack before starting the activity.
FLAG_ACTIVITY_NEW_TASK - Start the activity in a new task or reuse an existing task tied to that activity.
Intent i=new Intent(this, Sample.class);
i.setFlags(Intent. FLAG_ACTIVITY_NEW_TASK);
startActivity(i);

15. Intent Filters- Flags 2 How FLAG_ACTIVITY_NEW_TASK work:
With normal intent StartActivity
With FLAG_ACTIVITY_NEW_TASK:

16. Important Questions? Define Android intents? Ans : Slide 2
Mention mainly used of Android intents ? Ans : Slide 3
Explain the Types of Android Intents? Ans : Slide 4,5
Give Three examples of using Android Intents as : Ans : Slide 6
Use explicit intents?
Use implicit intent?
What are the elements of intent filter list them with short definition ? Ans : Slide 7
Give Three intent Action filter name and goal when apply on:
Activity? Ans : Slide 8
Broadcast Receiver? Ans : Slide 9
Define Data intent filter and Explain (URL or MIME ) with example? Ans : Slide 7,10
What is Category intent filter end explain only Two type of it? Ans : Slide 7,12
Explain Extras intent filter and write sample java code to implement it ? Ans : Slide 7, 13
Explain Flags intent filter and write sample java code to implement it ? Ans : Slide 7,14

17. Questions? Discussion?