Android Important Interview Question

 

✅ 1. Job Summary & Key Requirements Understanding

They expect:

• Android apps in Java

• React Native (cross-platform priority)

• APIs integration (REST, JSON)

• Firebase & Google APIs

• Databases (SQLite local, PostgreSQL server)

• Architecture patterns (MVP, MVVM)

• UI/UX skills

• Payment gateway integration

• Basic PHP knowledge

• Experience with HRMS, Education, Recruitment apps

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✅ 2. Most Expected Questions and Best Answers

Q1: Tell me about yourself as an Android Developer.

Answer:
“I have around 2–3 years of experience in Android development using Java and Android Studio, and I’ve also worked on cross-platform development with React Native. My expertise includes REST API integration using Retrofit, Firebase for authentication and real-time database, and Google APIs like Maps and Push Notifications. I have experience working on Educational apps and HRMS systems, where I implemented custom UI, MVVM architecture, and local database handling with SQLite. I am passionate about writing clean, maintainable code and delivering intuitive UI/UX.”

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Q2: How do you integrate REST API in Android?

Answer:
“I use Retrofit with OkHttp for API calls. For example:

• Step 1: Define the base URL in Retrofit.Builder().

• Step 2: Create an interface with endpoints using @GET, @POST, etc.

• Step 3: Call the API asynchronously and parse the JSON response into model classes using Gson.
  I also handle error responses, timeouts, and use interceptors for logging.”

✔ Example code snippet:

Retrofit retrofit = new Retrofit.Builder()
    .baseUrl("https://api.example.com/")
    .addConverterFactory(GsonConverterFactory.create())
    .build();

ApiService apiService = retrofit.create(ApiService.class);

Call<UserResponse> call = apiService.getUserData();
call.enqueue(new Callback<UserResponse>() {
    @Override
    public void onResponse(Call<UserResponse> call, Response<UserResponse> response) {
        if (response.isSuccessful()) {
            // Handle data
        }
    }
    @Override
    public void onFailure(Call<UserResponse> call, Throwable t) {
        // Handle error
    }
});

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Q3: What is MVVM and how is it different from MVP?

Answer:

• MVP (Model-View-Presenter) → Presenter handles UI logic, View is passive.

• MVVM (Model-View-ViewModel) → Uses Data Binding and LiveData, so View updates automatically when data changes.
  ✔ Advantage: MVVM reduces boilerplate and is better for reactive UI using ViewModel + LiveData.

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Q4: How do you handle local storage in Android?

Answer:

• For local storage: Use SQLite or Room Database.

• For key-value: Use SharedPreferences.

• Example: I have implemented Room DB with MVVM for offline data sync in an HRMS app.

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Q5: How do you implement Firebase in an Android app?

Answer:
“I have used Firebase for:

• Authentication (Email/Password, Google Sign-In)

• Realtime Database

• Push Notifications using Firebase Cloud Messaging

• Analytics for tracking user behavior
  I integrate Firebase SDK, configure it via google-services.json, and then call required APIs.”

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Q6: How do you implement Google Maps in Android?

Answer:

• Enable Google Maps API in console.

• Add the API key in manifest.

• Use MapFragment or SupportMapFragment.
  ✔ Example: Show user location, add markers, implement OnMapReadyCallback.

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Q7: How do you integrate a Payment Gateway in Android?

Answer:
“I’ve integrated Razorpay and Paytm:

• Add SDK in Gradle.

• Initialize with checkout.open(activity, options).

• Handle success/failure callbacks.
  ✔ Important: Always validate payment on the server using an API before confirming.”

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Q8: How do you optimize an Android app for performance?

Answer:

• Use View Binding instead of findViewById().

• Avoid memory leaks (use WeakReference, avoid static Context).

• Use DiffUtil for RecyclerView.

• Optimize network calls with caching and pagination.

• Compress images and use libraries like Glide for lazy loading.

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Q9: Do you know React Native?

Answer:
“Yes, I have experience building cross-platform apps using React Native. I’ve worked on:

• Navigation using react-navigation.

• API calls using Axios.

• Redux for state management.

• Android-specific modules for native functionality.”

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Q10: Explain JSON Parsing in Android.

Answer:
“I mostly use Retrofit with Gson for automatic JSON parsing. Alternatively, I can use JSONObject or Moshi for custom parsing.”

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Q11: How do you work with PostgreSQL in Android?

Answer:
“Direct connection is not recommended, so I use REST API (built in PHP or Node.js) to communicate with the PostgreSQL server. The app sends a request, and the backend interacts with the database.”

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Q12: What is Gradle and why do we use it in Android?

Answer:
“Gradle is the build system for Android. It:

• Manages dependencies

• Handles build variants

• Supports plugins like Kotlin, Hilt, etc.
  It uses DSL scripts (build.gradle) for configuration.”

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✅ 13. Bonus Questions You Might Get

• Q: What design patterns do you use in Android?
  ✔ A: MVP, MVVM, Singleton, Repository pattern.

• Q: How do you secure API keys in Android?
  ✔ A: Use NDK or EncryptedSharedPreferences, never hardcode keys.

• Q: What is your approach to debugging crashes?
  ✔ A: Use Logcat, Crashlytics, and adb commands.

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✅ 14. Practical Scenarios (They Might Ask You to Write or Explain)

• Login Screen with Retrofit + MVVM + LiveData

• Fetch Data from API and Show in RecyclerView

• Push Notifications with Firebase

• Payment Integration Example