Problem Statement
What are common anti-patterns or mistakes developers make with StatefulWidget lifecycle methods?
Explanation
A common mistake is calling setState() during build, initState, or dispose, which causes errors or unexpected behavior. Never call setState() in initState - instead, initialize state variables directly. Don't call setState() in dispose as the widget is being removed. Avoid calling setState() during build as it triggers infinite rebuild loops. Only call setState() in event handlers, callbacks, or lifecycle methods like didUpdateWidget.
Forgetting to call super methods in lifecycle overrides causes subtle bugs - always call super.initState(), super.dispose(), super.didUpdateWidget(), etc. Forgetting to dispose controllers, subscriptions, and listeners leads to memory leaks where resources stay in memory after the widget is removed, eventually causing performance degradation or crashes.
Not checking mounted property before setState() in async callbacks is a major source of errors. Long-running operations like network requests might complete after the user navigates away, trying to call setState() on a disposed widget. Always check if (mounted) before setState() in async contexts. Another mistake is doing expensive work in build() which should be fast and pure - move expensive operations to lifecycle methods or state changes.
Performing initialization that depends on BuildContext in initState() instead of didChangeDependencies() causes problems because context-dependent data isn't available yet. Using setState() to manage complex state instead of proper state management solutions makes code difficult to maintain and debug. Not understanding when widgets rebuild leads to performance issues from unnecessary rebuilds - use const constructors, break widgets into smaller pieces, and profile to identify bottlenecks.