Day 7/100: Week 1 Recap — 6 Android Fundamentals I Thought I Knew Cold

This is Day 7 of my 100 Days to Senior Android Engineer series. Every 7th day is a weekly recap — a structured summary of what I covered, what surprised me, and what I'm carrying into next week. Week 1 is done. Six topics. Six posts. And more gaps in my "solid" understanding than I expected to find. Here's the honest summary. What I covered this week Day Topic Key insight Day 1 Why I started this Knowing how vs knowing why Day 2 The 4 Android components Each is an OS entry point, not just a class Day 3 Activity Lifecycle onDestroy() is not guaranteed Day 4 Fragment Lifecycle Two lifecycles: Fragment + View Day 5 Intent, Task & Back Stack singleTask clears your back stack silently Day 6 Context Lifetime mismatch = memory leak The 6 most important things I (re)learned 1. Android components are entry points, not just classes When you declare an Activity, Service, BroadcastReceiver, or ContentProvider in AndroidManifest.xml, you're giving the OS a door into your app — one it can open i