1. The document discusses Android activities, which provide interactive screens for users to perform tasks. Activities are created by subclassing the Activity base class and implementing callback methods like onCreate. 2. The document also discusses how to navigate between activities using intents, and how activities transition through various lifecycle states like onStart and onStop. An example app with registration and login activities is provided to demonstrate navigation between activities. 3. The document explains how to use shared preferences to store persistent data in Android applications. Shared preferences can be accessed via the PreferenceManager and values can be read and written by getting and putting values with keys. An example demonstrates reading a value set in a previous app session.

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Activities, Intents
and
Shared Preferences
for
Persistence

2. SIMPLE ACTIVITY
• Activity
• Layout
• Using Layouts from Activity
• Activity to Activity Transition
• Activity Lifecycle
• Exercise
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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).
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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???
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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);
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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
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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
Activity 1 Activity 2
Intent intent_1_to_2 = new Intent(this, Activity2.class);
startActivity(intent_1_to_2);
Intent
Activity 1 Activity 2
Intent intent_2_to_1 = new Intent(this, Activity1.class);
startActivity(intent_2_to_1);
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8. Android Activities Exercise (Contd.)
How to navigate from one Activity to another
Intent
Activity 1 Activity 2
Intent intent1to2 = new Intent(this, Activity2.class);
startActivity(intent1to2);
Activity 1 Activity 2 Intent
Intent intent2to1 = new Intent(this, Activity1.class);
startActivity(intent2to1);
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9. Activity Lifecycle
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10. Activity Lifecycle (Contd.)
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11. Shared Preferences for Persistence
Android applications can store data in application preferences.
In this tutorial, you learn how to store persistent application data with shared preferences.
1. Preferences in Android are used to keep track of application and user preferences.
2. In any application, there are default preferences that can accessed through the
PreferenceManager instance and its related method
getDefaultSharedPreferences(Context)
3. With the SharedPreference instance one can retrieve the int value of the any preference
with the getInt(String key, int defVal).
4. In our case, we can modify the SharedPreference instance in our case using the
edit() and use the putInt(String key, int newVal)
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12. Shared Preferences for Persistence
We see an example of this:
1.We create a project:
2.We also create a layout
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13. Shared Preferences for Persistence
Here is our Activity
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14. Shared Preferences for Persistence
We read and write now:
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15. Shared Preferences for
Persistence
Now we run the app:
1. For testing we set a value
2. Exit application
3. Launch the app again
4. Retrieve the value
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16. Thank You.
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