technical-interview - GrindLoop: Android & iOS Interview Prep

Why Gson Returns Null Fields Only in Your Release Build

September 28, 2026 by Arsam

Code editor on a dark monitor showing JSON parsing code, illustrating Gson null fields in an Android release build

A Kotlin data class parsed by Gson works in debug and comes back null in release. Here’s the two-bug reason (R8 plus Gson skipping your constructor), the fix, and the interview answer.

Found the Bug in Your Android Debugging Interview and Still Didn’t Pass?

September 28, 2026 by Hass

Laptop showing a code editor next to a mobile emulator, the setup for an Android debugging interview

In an Android debugging interview, the first green test is often only the midpoint. What the bug squash round scores, and the traps that sink candidates who find the bug.

Why Fast Scrolling Duplicates Items in Your Paginated List

September 27, 2026 by Arsam

Close-up of code on a laptop screen, illustrating an Android pagination race condition bug

An Android pagination race condition duplicates list items when two scroll-triggered page loads overlap. Here’s the two-bug reason, the fix, and the interview answer.

Got an Exploding Offer While Your Other Android Loops Are Still Running?

September 27, 2026September 27, 2026 by Hass

Candidate marking an exploding offer deadline on a desk calendar while other interview loops are still running

An exploding offer usually lands while slower loops are still at the committee or team-matching stage. How to buy time, what to tell the other companies, and how to sequence loops so it doesn’t happen again.

Stuck in Team Matching After Passing the Android Loop? The Hiring Manager Call Has a Clock, Not a Rubric

September 26, 2026 by Hass

Engineer on a video call with a hiring manager during team matching

Team matching sits between a passed interview loop and an offer, and a candidacy can expire there. How the stage works at Google and Meta, and how an Android engineer should run it.

The Android Recruiter Screen Question That Quietly Sets Your Level

September 27, 2026September 25, 2026 by Hass

An engineer taking notes during an Android recruiter screen phone call at a desk with a laptop

The Android recruiter screen can set your level before any technical round. A vague and a specific answer to “walk me through your background,” and how to handle the pay question.

Why Your Kotlin Data Class’s equals() Ignores the Parent Class

September 27, 2026September 24, 2026 by Arsam

Close-up of colorful source code on a computer monitor

The Kotlin data class equals check ignores a parent class’s properties, by design. Why, the hashCode trap in the obvious fix, a correct override and the interview answer.

Why the Android Machine Coding Round Isn’t One Test, It’s Three

September 27, 2026September 23, 2026 by Hass

Close-up of code in a dark editor, the kind of work done in an Android machine coding round

The Android machine coding round comes in three formats: build from scratch, extend a codebase, and debug. What each one tests, and a scaffolding drill to run from an empty file.

Why viewModelScope.async Swallows a Failed API Call

September 27, 2026September 22, 2026 by Arsam

Network server rack with blinking status lights and ethernet cables, representing an async API call over the network

A viewModelScope async call that nobody awaits hides its failure completely. Why a root async stores the exception, why the same code inside launch crashes instead, a runnable repro and the fix.

Why Picking the Wrong Project to Talk About Can End an Android Hiring Manager Screen Early

September 27, 2026September 18, 2026 by Hass

Two interviewers looking at a resume while on a video call with a candidate during an Android hiring manager screen

The Android hiring manager screen often decides whether you get an onsite. What the manager listens for during your project walkthrough, and a sample walkthrough that holds up.