flutter row screen width code example
Example 1: set container height flutter 25% of screen
MediaQuery.of(context).size.height * 0.25
Example 2: flutter image size percentage
Expanded(child: Image.asset("assets/mypic.jpg")),
MediaQuery.of(context).size.height * 0.25
Expanded(child: Image.asset("assets/mypic.jpg")),