Android is an open source mobile platform launched by Google in 2008 and since then it has become the favorite of people and developers all over the world. Android is a multithreaded, multithreaded operating system based on Linux. Google’s Android OS isn’t limited to phones, but you can use it to build a DVR, handheld GPS, MP3 player, and so on.

Although the Android platform is open source and customizable, Android users and developers have become accustomed to Google-developed builds for Android devices. Using these Android concepts is vital to developing an app quickly.

The key concepts of Android are:-
Applications and APK files
Activities
Fragments
Views and View Groups
XML file layout
intentions
widgets
Services
sensors

I am giving you an overview of the key concepts of Android. After you have a basic understanding of the key Android concepts, you can dive deeper into the different topics.

Applications and APK files

An Android app is an Android app. An application is packaged in an APK file, that is, an Android application package. The APK file contains the compiled Java code and other resources such as images and text for the Android application.

Activities

An Android activity is a GUI component. You can think of it as a window in a desktop application. Since mobile phone screens are small, one activity takes up the entire screen. If you open multiple activities, they are stacked on top of each other. You can’t arrange activities side by side like you can with desktop windows.

Activities are single, focused actions that a user can perform. Since it’s difficult to scroll, zoom, or click links on a small screen, it’s recommended that an app display only one activity per screen. This will present the most relevant information to the user and allow them to launch a new screen for additional information or click the back button to view previous activity. The screen can expose multiple tasks, but should help the user complete only one activity at a time.

Fragments

In Android, a fragment is a piece of a total user interface. A fragment only takes up part of the screen. Fragments are used in activities. Fragments can also be used within different activities. Fragments contain Views and ViewGroups within them.

View and View groups

Android GUI elements are divided into three categories, namely activities, views and display groups. The activities are the windows/screens. Views are the individual elements of the GUI, such as a TextView that displays text, a button that users can click, and so on. ViewGroups are containers for Views. A ViewGroup actually groups a collection of Views together. Views and view groups can be nested within an activity or even within a fragment nested within an activity.

XML file layout

Activities, Fragments, and ViewGroups can use XML files to define their layout and content. Layout XML files indicate which GUI components an activity or fragment contains and also the style of the GUI components, i.e. size, margins, padding, etc.

Intention

If your app requires to perform a function beyond its core capabilities, such as opening a photo, playing a video, or searching for a contact, then you need to find out if a tool that can perform that function already exists in the operating system or in a third-party application. . If so, you can get the benefit of that functionality using intents.

For example, if your app accesses users’ contacts, you can use intent objects to launch the device’s existing contacts app. This eliminates programming duplication and also speeds up the user’s interaction with the device, since the user won’t need to relearn how to add a contact to your application.

widgets

Android widgets are actually GUI components that can be displayed outside of an activity. For example, a weather widget that displays today’s weather is displayed on many Android home screens. Widgets have been packaged and implemented as part of an Android application. Also, sometimes views in Android are also called widgets. For example, many GUI components are placed in a Java package called android.widget. GUI components are not the same as a widget that can stay on the home screen of an Android device. So you need to understand the difference between GUI components that can be used inside ViewGroups, Fragments and components that can be used inside ViewGroups, Fragments and Activities and also inside Widgets and Widgets that can stay on screen. Android device startup.

Services

On Android, Services are background processes that can be run on an Android device even if no app is visible. Services do not require a user interface. For example, a service might check a remote server for updates or backup data every hour.

sensors

Android devices have many built-in sensors that you can access from your Android apps. For example, the built-in GPS in smartphones is a sensor. Therefore, you can get access to GPS from inside your Android apps.