Android har en streng threading-modell sentrert rundt main (UI)-tråden — som må håndtere UI og holde seg responsiv. Å forstå threading, hvorfor arbeid må flyttes vekk fra main-tråden, og verktøyene (coroutines, og historisk threads/handlers) er viktig for responsive apper.
Main thread-regelen
Android has a single MAIN (UI) thread that:
→ handles ALL UI operations (drawing, events) — UI updates MUST happen on it
→ must stay RESPONSIVE — blocking it freezes the UI; >5s blocked = ANR (App Not Responding)
TWO key rules:
1. DON'T do long/blocking work on the main thread (network, DB, heavy compute) → move it off
2. DON'T update UI from a background thread → switch back to the main thread for UI
