Fix Flutter 'LateInitializationError: Field has not been initialized'

late is a promise to Dart that you will assign the field before anyone reads it. Break that promise and you get a LateInitializationError. Here are the three correct ways out.

Fix 1: Initialize in initState

late final AnimationController _controller;

@override
void initState() {
  super.initState();
  _controller = AnimationController(vsync: this); // assigned before use
}

Fix 2: Make It Nullable Instead

If the value genuinely may not exist yet, drop late and use a nullable type with null handling:

User? _user; // null until loaded
// ... later
Text(_user?.name ?? "Loading...");

Fix 3: Lazy Initialization

late final config = _buildConfig(); // computed on first read