Singularity-Coder / Instant-Android

List of Android Topics and their Examples!

Android Examples

A list of android samples on different topics!

Jetpack Compose

• (Kotlin) Basic ImageView and TextView in Jetpack Compose. Link
• (Kotlin) Creating a list with custom view holder with material theming. Link
• (Kotlin) Creating a chat list and maintaining local view states using remember and mutableState. Link
• (Kotlin) Compose permissions and Android Permissions. Link

Application Components

Activities & Fragments

• Fragment to Fragment communication through interfaces. Link
• (Kotlin) Activity and Fragment Lifecycles. Link

Services

• (Kotlin) Simple Foreground Service. Link
• (Kotlin) Start foreground service and stop it on device reboot.
• Foreground Service to control music playback. (Work in Progress) Link

Broadcast Receivers

• (Kotlin) Listen to all system broadcasts. Link
• (Kotlin) Send Broadcast on device reboot. Link
• (Kotlin) Send Local Broadcast from a JobIntentService. Link
• Send Local Broadcast from a JobIntentService. Link

Content Providers

• (Kotlin) Read SMS through content resolvers. Link
• (Kotlin) File Pickers. Link

Architecture Components

Data Binding & View Binding

• https://github.com/Singularity-Coder/Blog/tree/master/java/BoundbyData

View Model & Live Data

Paging

Work Manager

Room

• https://github.com/Singularity-Coder/Blog/tree/master/java/RoomNews
• https://github.com/Singularity-Coder/Blog/tree/master/java/Rooming

App & View Communication

• Sharing data between Fragments through Shared ViewModel. Link
• Sharing data between Fragments through Interfaces. Link
• Receive data from other Apps through Intent Filters. Link

Navigation Components

• https://github.com/Singularity-Coder/Blog/tree/master/java/NavigationComponents

Android Networking

Ktor

• (Kotlin) Simple Github API call using Ktor Library. Link

Volley

• https://github.com/Singularity-Coder/Blog/tree/master/java/VolleyNetworking
• https://github.com/Singularity-Coder/Blog/tree/master/java/VolleyNetworkingGSON
• https://github.com/Singularity-Coder/Blog/tree/master/java/VolleyNetworkingPOST

Retrofit

• (Kotlin) Simple API call using Retrofit Library with GSON converter - Part 1. Link
• (Kotlin) Simple API call using Retrofit Library with GSON converter - Part 2. Link
• https://github.com/Singularity-Coder/Blog/tree/master/java/RetrofitResponseObject
• https://github.com/Singularity-Coder/Blog/tree/master/java/RetrofitPOSTwithGSON
• https://github.com/Singularity-Coder/Blog/tree/master/java/RetrofitGETwithGSON
• https://github.com/Singularity-Coder/Blog/tree/master/java/POSTRetrofitting
• https://github.com/Singularity-Coder/Blog/tree/master/java/Retrofitting

HttpUrlConnection

• Fetch list of restaurants from Zomato API using HttpUrlConnection. Link

Tools

• Chucker to monitor http network stuff. Link

Android Data Storage

• A simple Room ORM example without any views. Link
• Storing newsapi.org news API info into SQLite through Room ORM and Retrofit. Link
• A simple todo list app using Room ORM. Link
• Todo list app using raw SQLite. Link
• (Kotlin) Realm No-SQL local database. Link

Dependency Injection

• (Kotlin) DI using Dagger Hilt, Retrofit, Room,etc. (Under Construction) Link

Firebase

Cloud Messaging

• Firebase Cloud Messaging (FCM) example. Link

Authentication

• Login using Firebase Email Authentication. Link
• Login using Firebase Google Authentication. Link

Storage

• Store and retrieve files using Firebase Storage. Link

Firestore

• Create a Grocery List App by performing CRUD operations. Link

Social Integration

• https://github.com/Singularity-Coder/Blog/tree/master/java/FirebaseGoogleAuth
• https://github.com/Singularity-Coder/Blog/tree/master/java/GoogleAuth

Real-Time App Messaging

• https://github.com/Singularity-Coder/Blog/tree/master/java/FirebaseCloudMessaging2

User Interface & User Experience

Shape Drawables, Fav Gradients, 9 patch images, material components, custom UI components, animations, transitions, canvas drawings, color palletes, custom styles, image scaling and transformation techniques, etc.

• https://github.com/Singularity-Coder/Blog/tree/master/java/ActionBarMenus
• https://github.com/Singularity-Coder/Blog/tree/master/java/AndroidAlertDialogs
• https://github.com/Singularity-Coder/Blog/tree/master/java/DateTimePickers
• https://github.com/Singularity-Coder/Blog/tree/master/java/FrescoImageView
• https://github.com/Singularity-Coder/Blog/tree/master/java/LottieAnimationsTutorial
• https://github.com/Singularity-Coder/Blog/tree/master/java/MutliViewList
• https://github.com/Singularity-Coder/Blog/tree/master/java/NavigationDrawer2
• https://github.com/Singularity-Coder/Blog/tree/master/java/RecyclerViewCustomHeader
• https://github.com/Singularity-Coder/Blog/tree/master/java/RxBindingViews
• https://github.com/Singularity-Coder/Blog/tree/master/java/ShimaShimaShima
• https://github.com/Singularity-Coder/Blog/tree/master/java/TabLayout
• https://github.com/Singularity-Coder/Blog/tree/master/java/ParallaxTabs
• https://github.com/Singularity-Coder/Blog/tree/master/java/LayoutParams
• https://github.com/Singularity-Coder/Blog/tree/master/java/OnClickListsners4Styles
• (Kotlin) https://github.com/Singularity-Coder/Blog/tree/master/kotlin/KotlinRecyclerView
• (Kotlin) https://github.com/Singularity-Coder/Android-Dialogs
• (Kotlin) Modal Bottom Sheet Link
• (Kotlin) Persistent Bottom Sheet Link
• (Kotlin) Multi Touch Link

Multi-Threading & Background Processing

• https://github.com/Singularity-Coder/Blog/tree/master/java/AndroidBackgroundProcessing

Utilities

Camera

• https://github.com/Singularity-Coder/Blog/tree/master/java/CameraXTest
• https://github.com/Singularity-Coder/Blog/tree/master/java/CustCam
• https://github.com/Singularity-Coder/Blog/tree/master/java/QRCodeScanner

Other Utilities

• https://github.com/Singularity-Coder/Blog/tree/master/java/RecordScreenLikeCrazy
• https://github.com/Singularity-Coder/Blog/tree/master/java/ShareImageText
• https://github.com/Singularity-Coder/Blog/tree/master/java/ShoworHidePassword
• https://github.com/Singularity-Coder/Blog/tree/master/java/Pagination
• https://github.com/Singularity-Coder/Blog/tree/master/java/NotificationGenerator
• https://github.com/Singularity-Coder/Blog/tree/master/java/TextToSpeechToTextApp
• https://github.com/Singularity-Coder/Blog/tree/master/java/FilterRecyclerViewLocally
• https://github.com/Singularity-Coder/Blog/tree/master/java/AndroidSearch
• Perform recurring tasks with Timer, Handler, Observable Timer & Interval, etc. Link
• (Kotlin) Creating custom toast on android Link
• (Kotlin) Logging on Android Link

Machine Learning

• https://github.com/Singularity-Coder/Blog/tree/master/java/GoogVizAPI

JSON Parsing

• https://github.com/Singularity-Coder/Blog/tree/master/java/OfflineJSON2
• https://github.com/Singularity-Coder/Blog/tree/master/java/LocalJSON

Location Services

• https://github.com/Singularity-Coder/Blog/tree/master/java/PlacePicker
• https://github.com/Singularity-Coder/Android-Examples/tree/master/java/GetLatLong
• https://github.com/Singularity-Coder/Android-Examples/tree/master/java/GetLocationUpdates
• https://github.com/Singularity-Coder/Android-Examples/tree/master/java/Geofencing

Protocol Buffers

• (Kotlin) Construct a basic object using Protobuf. Link
• (Kotlin) Deserialise data coming from an API with Protobuf. (Work in Progress) Link

Java Native Interface (JNI)

• (Kotlin) Fetching strings from native code to Kotlin code using JNI. Link

Testing

Espresso Testing

• https://github.com/Singularity-Coder/Blog/tree/master/java/RoomNews
• https://github.com/Singularity-Coder/Blog/tree/master/java/RetrofitPOSTwithGSON

Unit Testing

Airbnb Epoxy

• Basic Recycler View with dummy data Link

RxJava

• https://github.com/Singularity-Coder/Blog/tree/master/java/RxJavaNews
• Perform click events using Jake Wharton's RxBinding Library. Link

Gradle

• (Kotlin) BuildType and Build Flavors Link

CI/CD

Android Games

Android Performance Tools

Android App Ads

Payment Integration

Other

• https://github.com/Singularity-Coder/Blog/tree/master/java/PHPMySQLConnection

Programming Paradigms in Android

Reactive Programming

Functional Programming

Object-oriented Programming

Declarative Programming

Imperative Programming

Procedural Programming

Logic Programming

Modular Programming

Structured Programming

Generic Programming

Event-driven Programming

Aspect-oriented Programming

Prototype based Programming

Data-driven Programming

Function-level Programming

Array Programming

Dataflow Programming

Role-oriented Programming

Agent-oriented Programming

Stack oriented Programming

SOLID Principles in Android

Sigle Responsibility

Open/Closed

Liskov Substitution

Interface Segregation

Dependency Injection

Design Principles in Android

Loose coupling

Prefer Composition over Inheritance

Program to an Interface, not an implementation

Encapsulate what varies

Encapsulation

Abstraction

Polymorphism

Inheritance

Design Patterns in Android

Creational Patterns

• Abstract Factory Pattern Link1
• Builder Pattern KotlinLink1
• Factory Method Pattern Link1 Link 2
• Prototype Pattern
• Singleton Pattern Link1

Structural Patterns

• Adapter Pattern
• Bridge Pattern
• Composite Pattern
• Decorator Pattern
• Facade Pattern Link1
• Flyweight Pattern
• Proxy Pattern

Behavioural Patterns

• Chain of Responsibility Pattern
• Command Pattern
• Interpreter Pattern
• Iterator Pattern
• Mediator Pattern
• Memento Pattern
• Observer Pattern
• State Pattern
• Strategy Pattern
• Template Pattern
• Visitor Pattern

Architecture Patterns in Android

• MVVM Architecture (Model View ViewModel) Link
• MVP Architecture (Model View Presenter) Link
• MVC Architecture (Model View Controller) Link
• VIPER Architecture (View Interactor Presenter Entity Router) Link
• MVI Architecture (Model View Intent)
• Clean Architecture

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Android FAQ

I collected these questions from some medium article. I forgot to add the source at that time. I will attach it when I find it.

Activity/Fragment/Broadcast/Application/Service Lifecycle (Explain with one line description)

Which lifecycle method gets called when A goes to B/come back to A?Activity Launch Modes with examples

Let’s say 4 activities are there A->B->C->D. How to launch A from D finishing in between activities?

4 Activities are there A->B->C->D.How to finish application from D if none of the activities opened earlier finished till now?

How CLEAR_TOP flag intent works in android?

Service vs IntentService?When to prefer which type of service?

Explain ways for Activity to activity communication/Activity to fragment communication/Fragment to fragment communication.

How to make a service persist even after Application killed?

How to achieve Interprocess communication in android?

How Async task internally works? Async task implementation?

Cons of using Async task? How to overcome this limitation?

Why Job Scheduler?

Notification related changes in Oreo?

How to handle Background service and execution limits with new Oreo Updates?

Have you seen Google I/O 2018? What were the updates for Android there?

Why do we use Headless fragments?

Memory Leakage, Causes, and preventions in Android? I have written a blog out here.You can refer this too

Ways to optimize an Android Application.

Proguard-Obfuscation/ Minification, Build Variants, Flavours.

How to achieve MultiThreading in Android?

Suppose you have 10 images to fetch from Server. What is the best way to fetch images? (Hint: Read about ThreadPool and Executor)

Builder vs Factory Pattern with an example

Why MVP not MVC? They will ask you to make a wireframe kind of thing on paper to demonstrate MVP pattern in android.

Why RXJAVA so popular nowadays?

Problems in RXJAVA? They can provide you with some scenarios to get to know if you can find out the problems with it.

Map vs Flat map? (Most commonly asked in RXJAVA)

Should we provide a context in presenter/Model? Answering yes/no is not enough. You have to provide a solution for it.

Why Schedulers and How Rxjava internally works with them?SusbcribeOn vs ObserveOn, Schedulers on which both of these work?.subscribe(new Subscriber…) vs .subscribe(new Observer…)

IOScheduler/new Thread Scheduler in RXJava

How dagger internally worksDagger vs Dagger2? Explain the purpose of every annotation taken in Dagger2.

How do you decide scope in Dagger? Why Qualifier annotation?

Why do we use Handlers? Do you know the Loopers? What’s the role of Message queue? With this, they will go for Main Thread working. They will also ask you about the exceptions we get as Looper.prepare() exceptions

Cause of Memory leak during the Async Task?

Explain Singleton pattern. Problems with it and Handling. (hint: Double checked locking/synchronization)

Why do you prefer Retrofit over Volley? Why Picasso? Now they will ask all the third party libraries you have used. Be honest with your answer. They may go deep in any of those.

Why ConstraintLayout?Barriers vs Guidelines, Why Group/Chains?

Why do we prefer Framelayout for Fragments?

Why ANR?How to prevent it?

Do async.execute make threads in parallel or serial?

How to make a custom view in android? Explain lifecycle methods. Difference between onLayout/onMeasure.

Have you ever faced any issue with SingleInstance launch mode or example if you have used it? Providing real-life examples are preferred more.

When 1 fragment added over another-Explain lifecycle methods. Another question would be if you replace instead of adding it. The 3rd question will be if you have back stack there.

Why fragment newInstance() is there (Best practice for instantiating a new Android Fragment)

Suppose you have to update location every minute even if you don’t get permission. But the tricky thing here is how will you notify the server-Through the same service you were sending updates using FusedLocationProvider/Will you use some other service or broadcast. Just design the whole thing.

Observable.just/Observable.from/Observable.create in RXJAVA?

Why Instant Apps? How do you achieve this?

How to load Large Bitmaps? Handle Memory leaks and Sample sizing

How parcelable internally works? Design it.

What happens if your serializable class contains a member which is not serializable? How to handle it?

Why do we use WeakReferences?

How to retain data on orientation change? Explain lifecycle during orientation changes.

How to make endless circular recyclerView?

Suppose you have given an array of array of custom Objects. Which data structure will you use to show these on UI?

How do you handle opening activity using notifications?

How to achieve Push notifications in android? Explain behavior during App in front/Background-How to handle both scenarios.

How to download files in parallel?

Why Realm?Realm Methods, Realm vs Sqlite.

How to handle different screen sizes/density/languages/orientation in android?

What the Fragment’s method setRetainInstance(boolean) does?

Keep yourself up to date with the latest library versions if using.

Why is there a need for JobIntentService?(hint:: Oreo update)

Basics for Testing in Android-They will ask some questions about Espresso,mockito,roboelectric(not in that deep).Stub vs mock. Also if you are following MVP pattern. Be prepared for the questions now.

How the OS handles process flow. When is the app killed or removed from recent memory? How OS decides this.

Which method gets called when home button pressed, back pressed etc.(Most commonly asked)

Manifest related attributes -allowBackup,intent-filters,process,taskAffinity,permission vs uses-permission etc.

Draw a simple basic design you follow to make an android application(folder structure, methods, variables)

Why services preferred over Broadcast receiver for background applications

Broadcast-related changes in Oreo and Handling them.

Accessibility services in android. How do you handle system apps(I mentioned this work too, so asked)

Thread.start() vs run method,submit vs Execute ,callable vs runnable

View Holder pattern.ListView vs RecyclerView.

Remote Views and How to use them?

Inner Classes vs Static Classes?

Volatile vs Transient

Internal Implementation of Picasso, Glide

Internal implementation of Recyclerview

Design Patterns and Practical Usage

Custom View and Lifecycle

Singleton vs Static and why we use them?

Deep vs Dynamic Linking

Livedata postValue vs set

Livedata vs ObservableField

ViewModelFactory

HashCode and Equals Implementation

Dagger - Component vs SubComponenets

TDD and frameworks - if using , tell the challenges faced

GSON vs Jackson vs Moshi

MultiModule Benfeits

Android Bundle - and Dynamic Feature usage

Proguard vs R8

What is Scoped Storage and how to implement?

Observable vs Completable vs Single

Rx vs Coroutines. Which one you prefer and when?

Difference between MVP and MVVM?

Explain SOLID principles?

Difference between const and val

When is onPause() called without onStop() being called?

Dagger vs Koin?

Any 5 RxJava operatrs. How subscribeOn and observeOn works?

Headless Fragments.

Workmanager, type of requests, methods, minimum interval before a job repeat itself.

Workmanager vs JobScheduler.

Why ConstraintLayout? Tell some properties which I find worth.

How SharedPreferences work internally?

You will be given assignments as your first/last round. They just want to know how you follow the standards. Some ask for UI thing, other ask for architectural patterns. Just check your methods and play well with the logic.That’s all.