The Activity is the big kahuna of the Android application. It serves as an entry point kinda like the Java main method. It is one of the fundamental building blocks of the Android system.

An Activity is basically a screen (UI) in an Android app. There are one or more Activities in an application. One Activity is designated the main Activity and therefore calls other components.

An Activity is implemented as a subclass of the Activity class.

Activities in an app are only loosely bound. There should be a minimal amount of dependancies between Activities. This is because an Activity may start an Activity from another app.

Activities must be defined in the apps Mainifest.xml file.

<manifest...>
   <application...>
      <activity...>
      </activity>
   </application>
</manifest>

Each Activity of an application must be defined in the manifest file. Activity is a child of Application.

List of attributes to accompany the Activity tag. All attributes are prefixed with android:. Example - allowEmbedded would actually be android:allowEmbedded="true".

allowEmbedded	boolean
allowTaskReparenting	boolean
alwaysRetainTaskState	boolean
autoRemoveFromRecents	boolean
banner	drawable resource
clearTaskOnLaunch	boolean
configChanges	mcc, mnc, locale, touchscreen, keyboard, keyboardHidden, navigation, screenLayout, fontScale, uiMode, orientation, screenSize, smallestScreenSize
directBootAware	boolean
documentLaunchMode	intoExisting, always, none, never
enabled	boolean
excludeFromRecents	boolean
exported	boolean
finishOnTaskLaunch	boolean
hardwareAccelerated	boolean
icon	drawable resource
label	string resource
launchMode	standard, singleTop, singleTask, singleInstance
maxRecents	integer
multiprocess	boolean
name	string
noHistory	boolean
parentActivityName	string
persistableMode	persistRootOnly, persistAcrossReboots, persistNever
permission	string
process	string
relinquishTaskIdentity	boolean
resizeableActivity	boolean
screenOrientation	unspecified, behind, landscape, portrait, reverseLandscape, reversePortrait, sensorLandscape, sensorPortrait, userLandscape, userPortrait, sensor, fullSensor, nosensor, user, fullUser, locked
showForAllUsers	true, false
stateNotNeeded	true, false
supportsPictureInPicture	true, false
taskAffinity	string
theme	resource or theme
uiOptions	none, splitActionBarWhenNarrow
windowSoftInputMode	stateUnspecified, stateUnchanged, stateHidden, stateAlwaysHidden, stateVisible, stateAlwaysVisible, adjustUnspecified, adjustResize, adjustPan