| Android Code Palace

Tuesday, December 06, 2011

Activity In Android :

What is an Activity ?

User interface of an application displayed on a device through an activity.
For each unique screen we have to create an activity.
When we run any application on our device(android smartphones, mobile devices or tablet pc) and moving one screen to another screen then there is a bunch of activities works internally.
There will be create a stack(called as backstack) and performing push-pop action with activities. When new activity creates , it pushed into backstack and poped from it by pressing "Back" button.
When we want to create a new activity , we have to extend the "Activity" class.

Source Code of an Activity :

import android.app.Activity;
import android.os.Bundle;
 
public class MyFirstActivity extends Activity 
{
  /** Called when the activity is first created. */
  @Override
  public void onCreate(Bundle savedInstanceState) 
  {
      super.onCreate(savedInstanceState);
  }
}

Life Cycle of an Activity :

You can easily understand the life cycle of an activity by this figure :

Note :- Adding dashed lines for <<kill>> , those indicate that OS may kill the activity when resources are low, so onStop() and/or onDestroy() might not be called.