Activity In Android

•An activity presents a visual user interface for one focused endeavor the  user can undertake.

•An application might consist of just one activity or many.

•Each one is implemented as a subclass of the Activity base class

An Activity is an application component that provides a screen with which users can interact in order to do something, such as dial the phone, take a photo, send an email, or view a map. Each activity is given a window in which to draw its user interface. 

An application usually consists of multiple activities that are loosely bound to each other. 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. Each activity can then start another activity in order to perform different actions. Each time a new activity starts, the previous activity is stopped, but the system preserves the activity in a stack (the "back stack"). When a new activity starts, it is pushed onto the back stack and takes user focus.. 

Declaring Activity In Manifest

<manifest ... >
  <application ... >
      <activity android:name=".ExampleActivity" />
      ...
  </application ...> 

</manifest >

Using Intent Filters  In Activity Tag

<activity android:name=".ExampleActivity" android:icon="@drawable/app_icon">
    <intent-filter>
        <action android:name="android.intent.action.MAIN" />
        <category android:name="android.intent.category.LAUNCHER" />
    </intent-filter>

</activity> 

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). 

Starting An Activity:

You can start another activity by calling startActivity(), passing it an Intent that describes the activity you want to start. The intent specifies either the exact activity you want to start or describes the type of action you want to perform

     Intent intent = new Intent(this, SignInActivity.class);
startActivity(intent); 

Implementing the lifecycle callbacks:

When an activity transitions into and out of the different states described above, it is notified through various callback methods. All of the callback methods are hooks that you can override to do appropriate work when the state of your activity changes. The following skeleton activity includes each of the fundamental lifecycle methods:

public class ExampleActivity extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // The activity is being created.
    }
    @Override
    protected void onStart() {
        super.onStart();
        // The activity is about to become visible.
    }
    @Override
    protected void onResume() {
        super.onResume();
        // The activity has become visible (it is now "resumed").
    }
    @Override
    protected void onPause() {
        super.onPause();
        // Another activity is taking focus (this activity is about to be "paused").
    }
    @Override
    protected void onStop() {
        super.onStop();
        // The activity is no longer visible (it is now "stopped")
    }
    @Override
    protected void onDestroy() {
        super.onDestroy();
        // The activity is about to be destroyed.
    }
}

More Android Topics

Android : Introduction



       Eclipse Setup for Android Development

                     Configuring Eclipse for Android Development



          Begging With Android

                     Creating Your First Android Project

                     Understanding Android Manifest File of your android app





         Working With Layouts

                      Understanding Layouts in Android

                          Working with Linear Layout (With Example)

                                Nested Linear Layout (With Example)

                          Table Layout

                          Frame Layout(With Example)

                         Absolute Layout

                         Grid Layout





       Activity

                     Activity In Android

                     Activity Life Cycle

                     Starting Activity For Result

                     Sending Data from One Activity to Other in Android

                     Returning Result from Activity



     Working With Views

                     Using Buttons and EditText in Android 

                     Using CheckBoxes in Android 

                     Using AutoCompleteTextView in Android

                     Grid View



     Dialogs In Android

                     Working With Alert Dialog

                     Adding Radio Buttons In Dialog

                     Adding Check Boxes In Dialog

                     Creating Customized Dialogs in Android

                    Adding EditText in Dialog



                   Creating Dialog To Collect User Input



                 DatePicker and TimePickerDialog

                              Using TimePickerDialog and DatePickerDialog In android



    Working With SMS

                  How to Send SMS in Android

                  How To Receive SMS

                  Accessing Inbox In Android



    ListView:

               Populating ListView With DataBase



      Menus In Android

                    Creating Option Menu

                    Creating Context Menu In Android



      TelephonyManager

                    Using Telephony Manager In Android



     Working With Incoming Calls

                    How To Handle Incoming Calls in Android

                    How to Forward an Incoming Call In Android

                   CALL States In Android



    Miscellaneous

                   Notifications In Android

                   How To Vibrate The Android Phone

                   Sending Email In Android

                  Opening a webpage In Browser

                   How to Access PhoneBook In Android

                   Prompt User Input with an AlertDialog



   Storage:  Storing Data In Android



               Shared Prefferences  In Android

                             SharedPreferences In Android



               Files: File Handling In Android

                              Reading and Writing files to Internal Stoarage

                              Reading and Writing files to SD Card 

                           

                DataBase : Working With Database

                             Working With Database in Android

                             Creating Table In Android

                             Inserting, Deleting and Updating Records In Table in Android

                             How to Create DataBase in Android

                             Accessing Inbox In Android



     Animation In Android:

                  Animating A Button In Android