Answers for "Viewports expand in the cross axis to fill their container and constrain their children to match their extent in the cross axis. In this case, a horizontal viewport was given an unlimited amount of vertical space in which to expand."

Viewports expand in the cross axis to fill their container and constrain their children to match their extent in the cross axis. In this case, a horizontal viewport was given an unlimited amount of vertical space in which to expand.

Column(
  children: <Widget>[
    Expanded( // wrap in Expanded
      child: ListView(...),
    ),
  ],
)
//Or
Column(
  children: <Widget>[
    SizedBox( // wrap in SizedBox with fixed height
  		height: 300,
      	child: ListView(...),
    ),
  ],
)