Try below code hope its helpful to you. refer TextCapitalization Here
- Capital first letter
TextCapitalization.words - Capital each letter
TextCapitalization.characters - Capital first letter of textfield
TextCapitalization.sentences - Default lowercase letter of textfield
TextCapitalization.none
Your Widget:
TextField(
textCapitalization: TextCapitalization.words,
decoration: InputDecoration(
border: OutlineInputBorder(
borderRadius: BorderRadius.circular(10),
),
prefixIcon: Icon(
Icons.search,
),
hintText: 'Search',
),
),
Result screen using TextCapitalization.words: 
Result screen using TextCapitalization.characters: 
Result screen using TextCapitalization.sentences: 
Result screen using TextCapitalization.none: 