Try this way
Row( mainAxisAlignment: MainAxisAlignment.center, children: <Widget>[ Container( width: 40, height: 40, child: GestureDetector( onTap: (){ }, child: Ink( decoration: const ShapeDecoration( color: Colors.lightGreen, shape: CircleBorder(), ), child: Icon(Icons.add,color: Colors.white,) ), ), ), Text('KG : 5'), Container( width: 40, height: 40, child: GestureDetector( onTap: (){ }, child: Ink( decoration: const ShapeDecoration( color: Colors.lightGreen, shape: CircleBorder(), ), child: Icon(Icons.add,color: Colors.white,) ), ), ), ], ),

Just out of curiosity I've taken a look at what happens under the hood, and I've used [dtruss/strace][1] on each test.
C++
./a.out < in Saw 6512403 lines in 8 seconds. Crunch speed: 814050
syscalls `sudo dtruss -c ./a.out < in`
CALL COUNT __mac_syscall 1 <snip> open 6 pread 8 mprotect 17 mmap 22 stat64 30 read_nocancel 25958

Python
./a.py < in Read 6512402 lines in 1 seconds. LPS: 6512402
syscalls `sudo dtruss -c ./a.py < in`
CALL COUNT __mac_syscall 1 <snip> open 5 pread 8 mprotect 17 mmap 21 stat64 29
[1]: http://en.wikipedia.org/wiki/Strace