The document discusses Android application development and activities. It covers: - The structure of Android applications which typically consist of multiple activities with one specified as the main activity in the Android manifest. - Activities provide an interactive screen for users to perform tasks. Creating an activity involves subclassing the Activity class and implementing callback methods like onCreate. - The user interface of an activity is defined through layouts which can be accessed from the activity class. - Activities can transition to one another using intents, by calling startActivity and passing an intent specifying the destination activity class. - An example is provided to create a registration and login activity, demonstrating how to add activities and navigate between them using intents

1. Android Application Development
Being Active Through Activities & Intents
Ahsanul Karim
ahsanul.karim@sentinelbd.com
Sentinel Solutions Ltd.
http://www.sentinelbd.com

2. Today We’re Covering…
• Application Structure
• Android Application Anatomy
• Activity
• Layout
• Using Layouts from Activity
• Activity to Activity Transition
• Activity Lifecycle
• Exercise

3. Android Activities
Activity
Activity provides a user generally with an interactive screen to do something like:
Dialing the phone, View a map List of something for user to select or Anything you
want your user to do
• An application usually consists of multiple activities.
• Typically, one activity in an application is specified as the "main" activity,
which is presented to the user when launching the application for the first
time. (which is specified in AndroidMenifest.xml)
The <action> element specifies that this is the "main" entry point to the application.
The <category> element specifies that this activity should be listed in the system's application
launcher (to allow users to launch this activity).

4. Android Activities (Contd..)
Creating Activity
We have already created Activities. But how did we create it?
Let’s revisit…
1. We created subclass of Activity base class
2. We implemented one callback method onCreate
Open Questions:
1. What is creating subclass???
2. What is callback methods???

5. Android Activities (Contd..)
Next Step: Implementing User Interface
1. Design res/layout/yourlayout.xml
2. Use Views from Activity class
Next Step: Implementing User Interface
<manifest ... >
<application ... >
<activity android:name=".ExampleActivity" />
...
</application ... >
...
</manifest >
Next Step: Starting Activity
We can start another activity by calling startActivity(), passing it an Intent that describes the
activity you want to start.
Intent intent = new Intent(this, ToActivity.class);
startActivity(intent);

6. Android Activities Exercise
1. We’ll make 2 Activities
2. Registration with basic features and validation:
1. Email address
2. First Name, Last Name
3. Date of Birth
4. Password
5. Confirm Password
6. I agree to terms and conditions
7. Buttons: Cancel, Submit
3. Login
1. Email address
2. Password
3. Buttons: New User, Login
(To be added: Remember me)
Link: http://developer.android.com/guide/appendix/faq/commontasks.html

7. Android Activities Exercise (Contd.)
1. How to add new Activities to the application
2. How to navigate from one Activity to another
How to navigate from one Activity to another
Intent
Intent intent_1_to_2 = new Intent(this, Activity2.class);
startActivity(intent_1_to_2);
Intent
Intent intent_2_to_1 = new Intent(this, Activity1.class);
startActivity(intent_2_to_1);

8. Android Activities Exercise (Contd.)
How to navigate from one Activity to another
Intent
Intent intent1to2 = new Intent(this, Activity2.class);
startActivity(intent1to2);
Intent
Intent intent2to1 = new Intent(this, Activity1.class);
startActivity(intent2to1);

9. Activity Lifecycle

10. Activity Lifecycle (Contd.)