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. code example

Example: 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(...),
    ),
  ],
)