Hire Top 1% Android App Developers & Engineers in 24 hrs

Android is a robust Linux-based operating system used on almost all smartphones and tablets. Android is widely used in developing and running apps with basic and advanced functionalities. The components of Android are - 

• Activities - Activities is a screen that represents the Graphical User Interface (GUI) of an application on which the users can operate or request any kind of data.
• Services - Services perform backend tasks,
• Content-providers - Content-providers share the data among multiple applications.
• Broadcast receivers - It is a mechanism that listens to system-level events like listening to incoming SMS, calls and more by the host application.

• Android is open-source i.e, you can access it without paying for it.
• Android is platform-independent, i.e., applications can be developed without depending on any external operating system with the help of Android Studio and Android Software development Kit (SDK).
• Android supports Wi-Fi, Bluetooth, Camera, Speech, Google Chrome, Youtube, etc.
• An android app developer freelancer can launch their apps on several platforms Google Playstore, Opera mobile store, Amazon app store, Mobango, SlideMe, etc.
• Android uses a very optimized virtual machine which is Android Runtime (ART) which makes applications faster by reducing the startup time of applications.

An activity is a single-focused screen representing the Graphical User Interface (GUI) of an application. It allows users to interact with the functionalities of that application, for example, dial a phone number, send an email, take a photo, make a google search, etc.

• An activity is a graphical user interface that provides a layer for users to interact with an application while a service performs back-end functions and has nothing to do with GUIs.
• Even if a user switches its application and opens up another activity, the service will continue to run in the background.
• A window assigned to a particular activity may be of fixed size to the windows or slide up and down but service can be used even when the activity window is not present.

• onCreate()  - This method is called when the user creates an activity. Using OnCreate(), the views are created and the data gets loaded from bundles.
• onStart() - It is invoked when the activity becomes visible to the user. If the activity is displayed to the user, then the onResume() function is invoked and if it is hidden then the onStop() method is invoked.
• onResume() - onResume() is invoked when the user begins to interact with the activity like dialing a phone number, sending an email, etc.
• onPause() - onPause() is called when the activity is being put to the background but not stopped till yet.
• onStop() - onStop() is called when the activity is not visible to the user anymore.
• onDestroy() - This method is invoked when the user finishes the activity.
• onRestart() - This method is called after the activity is finished and the user restarts the activity.

Activity intent is the message that is shared between components like content providers, activities, services, broadcast receivers, etc. The intent is often used with startActivity() to call an activity, service, content provider, etc. It is used to provide dynamic/run-time binding between the program code in different applications. For example, searching a location on the browser and being directed to Google Maps requires passing of an intent to the system to navigate between different activities within one application or between different applications in an Android Application Environment. 

Intents could be implicit intent or explicit intent. 

• Implicit Intent - Implicit intent invokes the actions using the system components without specifying them.

For example, if you want to open a webpage, you just type the name of that page and click on Go and the page is opened. Here no component is specified.

• Explicit Intent - Explicit intent provides the external class that needs to be invoked and specifies the components.

For example, there are two activities - FirstActivity and SecondActivity. There is one button on the FirstActivity naming “Go to other activity”, so you can move to SecondActivity. There is another button on the SecondActivity naming “Go to Home”, so you reach the FirstActivity. This is achieved using Explicit Intent.

The Dalvik Virtual Machine (DVM) is the running environment to execute Android applications. It follows the register-based model which is much faster in executing applications than the stack-based model followed by JVM which takes more memory and is slower than DVM. 

With the help of DVM, a device can run multiple instances of the Dalvik Virtual Machine with multiple applications which makes the applications run faster as compared to JVM where only one instance of the Java Virtual Machine is shared with multiple applications.

A Service is an Android component that performs long-running backend tasks while Thread is an operating system feature that allows you to execute tasks in the background. 

If the service gets destroyed in the middle, then Android ensures to restart it if you return START_REDELIVER_INTENT or START_STICKY from the onStartCommand() but if a thread is destroyed in the middle of an application due to low memory, the Android doesn’t ensure to restart it.

Service is an Android component so it considers the service priority before killing/destroying a particular application due to low memory while a thread is not an Android component so Android doesn’t consider the thread priority while destroying that application.

If you are trying to hire a Android Developer. Here is the Android Developer Job Description that you can use in your hiring.