Since: API Level 1
package

android.app

Contains high-level classes encapsulating the overall Android application model.

An Android application is defined using one or more of Android's four core application components. Two such application components are defined in this package: Activity and Service. The other two components are from the android.content package: BroadcastReceiver and ContentProvider.

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. An activity can start other activities, including activities that live in separate applications.

A Service is an application component that can perform long-running operations in the background without a user interface. For example, a service can handle network transactions, play music, or work with a content provider without the user being aware of the work going on.

The Fragment class is also an important part of an application's design—especially when designing for large screen devices, such as tablets. A fragment defines a distinct part of an activity's behavior, including the associated UI. It has its own lifecycle that is similar to that of the activity and can exist alongside other fragments that are embedded in the activity. While an activity is running, you can add and remove fragments and include each fragment in a back stack that's managed by the activity—allowing the user to navigate backwards through the fragment states, without leaving the activity.

This package also defines application utilities, such as dialogs, notifications, and the action bar.

For information about using some the classes in this package, see the following documents: Activities, Services, Fragments, Using the Action Bar, Creating Dialogs, and Notifying the User.

Interfaces

ActionBar.OnMenuVisibilityListener Listener for receiving events when action bar menus are shown or hidden. 
ActionBar.OnNavigationListener Listener interface for ActionBar navigation events. 
ActionBar.TabListener Callback interface invoked when a tab is focused, unfocused, added, or removed. 
DatePickerDialog.OnDateSetListener The callback used to indicate the user is done filling in the date. 
FragmentBreadCrumbs.OnBreadCrumbClickListener Interface to intercept clicks on the bread crumbs. 
FragmentManager.BackStackEntry Representation of an entry on the fragment back stack, as created with FragmentTransaction.addToBackStack()
FragmentManager.OnBackStackChangedListener Interface to watch for changes to the back stack. 
KeyguardManager.OnKeyguardExitResult Callback passed to exitKeyguardSecurely(KeyguardManager.OnKeyguardExitResult) to notify caller of result. 
LoaderManager.LoaderCallbacks<D> Callback interface for a client to interact with the manager. 
PendingIntent.OnFinished Callback interface for discovering when a send operation has completed. 
SearchManager.OnCancelListener See setOnCancelListener(SearchManager.OnCancelListener) for configuring your activity to monitor search UI state. 
SearchManager.OnDismissListener See setOnDismissListener(SearchManager.OnDismissListener) for configuring your activity to monitor search UI state. 
TimePickerDialog.OnTimeSetListener The callback interface used to indicate the user is done filling in the time (they clicked on the 'Set' button). 

Classes

ActionBar This is the public interface to the contextual ActionBar. 
ActionBar.LayoutParams Per-child layout information associated with action bar custom views. 
ActionBar.Tab A tab in the action bar. 
Activity An activity is a single, focused thing that the user can do. 
ActivityGroup A screen that contains and runs multiple embedded activities. 
ActivityManager Interact with the overall activities running in the system. 
ActivityManager.MemoryInfo Information you can retrieve about the available memory through getMemoryInfo(ActivityManager.MemoryInfo)
ActivityManager.ProcessErrorStateInfo Information you can retrieve about any processes that are in an error condition. 
ActivityManager.RecentTaskInfo Information you can retrieve about tasks that the user has most recently started or visited. 
ActivityManager.RunningAppProcessInfo Information you can retrieve about a running process. 
ActivityManager.RunningServiceInfo Information you can retrieve about a particular Service that is currently running in the system. 
ActivityManager.RunningTaskInfo Information you can retrieve about a particular task that is currently "running" in the system. 
AlarmManager This class provides access to the system alarm services. 
AlertDialog A subclass of Dialog that can display one, two or three buttons. 
AlertDialog.Builder  
AliasActivity Stub activity that launches another activity (and then finishes itself) based on information in its component's manifest meta-data. 
Application Base class for those who need to maintain global application state. 
DatePickerDialog A simple dialog containing an DatePicker
Dialog Base class for Dialogs. 
DialogFragment A fragment that displays a dialog window, floating on top of its activity's window. 
DownloadManager The download manager is a system service that handles long-running HTTP downloads. 
DownloadManager.Query This class may be used to filter download manager queries. 
DownloadManager.Request This class contains all the information necessary to request a new download. 
ExpandableListActivity An activity that displays an expandable list of items by binding to a data source implementing the ExpandableListAdapter, and exposes event handlers when the user selects an item. 
Fragment A Fragment is a piece of an application's user interface or behavior that can be placed in an Activity
FragmentBreadCrumbs Helper class for showing "bread crumbs" representing the fragment stack in an activity. 
FragmentManager Interface for interacting with Fragment objects inside of an Activity  
FragmentTransaction API for performing a set of Fragment operations. 
Instrumentation Base class for implementing application instrumentation code. 
Instrumentation.ActivityMonitor Information about a particular kind of Intent that is being monitored. 
Instrumentation.ActivityResult Description of a Activity execution result to return to the original activity. 
IntentService IntentService is a base class for Services that handle asynchronous requests (expressed as Intents) on demand. 
KeyguardManager Class that can be used to lock and unlock the keyboard. 
KeyguardManager.KeyguardLock Handle returned by newKeyguardLock(String) that allows you to disable / reenable the keyguard. 
LauncherActivity Displays a list of all activities which can be performed for a given intent. 
LauncherActivity.IconResizer Utility class to resize icons to match default icon size. 
LauncherActivity.ListItem An item in the list  
ListActivity An activity that displays a list of items by binding to a data source such as an array or Cursor, and exposes event handlers when the user selects an item. 
ListFragment A fragment that displays a list of items by binding to a data source such as an array or Cursor, and exposes event handlers when the user selects an item. 
LoaderManager Interface associated with an Activity or Fragment for managing one or more Loader instances associated with it. 
LocalActivityManager Helper class for managing multiple running embedded activities in the same process. 
NativeActivity Convenience for implementing an activity that will be implemented purely in native code. 
Notification A class that represents how a persistent notification is to be presented to the user using the NotificationManager
Notification.Builder Builder class for Notification objects. 
NotificationManager Class to notify the user of events that happen. This is how you tell the user that something has happened in the background.  
PendingIntent A description of an Intent and target action to perform with it. 
ProgressDialog

A dialog showing a progress indicator and an optional text message or view. 

SearchableInfo Searchability meta-data for an activity. 
SearchManager This class provides access to the system search services. 
Service A Service is an application component representing either an application's desire to perform a longer-running operation while not interacting with the user or to supply functionality for other applications to use. 
TabActivity An activity that contains and runs multiple embedded activities or views. 
TimePickerDialog A dialog that prompts the user for the time of day using a TimePicker
UiModeManager This class provides access to the system uimode services. 
WallpaperInfo This class is used to specify meta information of a wallpaper service. 
WallpaperManager Provides access to the system wallpaper. 

Exceptions

Fragment.InstantiationException Thrown by instantiate(Context, String, Bundle) when there is an instantiation failure. 
PendingIntent.CanceledException Exception thrown when trying to send through a PendingIntent that has been canceled or is otherwise no longer able to execute the request.