Android Development: Languages and App Components

• Some of the programming languages used in Android development are C++, Swift, Kotlin, Java, and C#.
• C++ is similar to C# and Java, which makes it convenient for programmers to transition to C++ or the other way around.
• Swift is the official programming language for iOS.
• Kotlin combines object-oriented and functional programming features.
• Kotlin uses val which never changes and var which can change, to declare variables.
• App components are the essential building blocks of an Android app.
• Activity is the entry point for user interaction and represents a single screen with a user interface. Example of an email viewing activity.
• Service runs in the background for long-running operations. Example of playing background music while using another app.
• Broadcast receiver enables the system to deliver events to the app outside of a regular user flow, allowing the app to respond to system-wide broadcasts.
• Content provider manages a shared set of app data that can be stored and accessed by applications.
• App activities, services, and broadcast receivers are activated by intents.
• Intent is a message defined by an Intent object that describes an action to perform, including the data to be acted upon, the category of component, and other instructions.

The Manifest File

• The manifest file (AndroidManifest.xml) contains details that exists in an app's components.
• The <manifest> element is the root element of the AndroidManifest.xml file.
• The <application> element contains sub-elements that declare each of the application's components and attributes that affect all the components.
• The required elements in the manifest file are <manifest> and <application>, which should occur only once.
• The <application> element must be the last element inside the <manifest> element.
• The icon and label that are set in the <application> element are the default icon and label for each of the app's components.
• The app's package name must be declared in a manifest file (ex. package="com.example.myapplication").
• The app's components must be declared in the manifest file (<activity> for each subclass of Activity, <service> for each subclass of Service, <receiver> for each subclass of BroadcastReceiver, <provider> for each subclass of ContentProvider, etc.)
• Permissions that the app needs in order to access protected parts of the system or other apps (ex. ` ) must be declared in the manifest file.
• Hardware and software features used or required by the app must be declared in the manifest file (Ex. `)
• The <intent-filter> element specifies the types of intents that an activity, service, or broadcast receiver can respond to.
• The <action> element adds an action to an intent filter while <category> adds a category name to an intent filter.