🐦 Flutter / Dart errors

Flutter and Dart errors — layout overflows, state lifecycle, null safety and build problems.

Code	Error	What it means
Null check operator used on a null value	Dart/Flutter: Null check operator used on a null value	The ! operator was applied to a variable that was null at runtime.
A RenderFlex overflowed	Flutter: A RenderFlex overflowed by x pixels on the right/bottom	A Row or Column’s children need more space than available, so Flutter draws the yellow-black overflow stripes.
setState() called after dispose()	Flutter: setState() called after dispose(): _MyState#1a2b3 (lifecycle state: defunct, not mounted)	An async callback (network, timer, stream) finished after the widget was removed and then called setState.