.dart

 Positioned(
        bottom: 0,
        child: AnimatedContainer(
          height: _expanded ? 800 : 210,
          duration: Duration(milliseconds: 500),
          curve: Curves.easeInOut,
          child: NewsList(
              articles: vm.newsArticles,
              onHeaderTapped: () {
                setState(() {
                   _expanded = !_expanded; 
                });
              },
              onDragUpdate: (details) {

              if(details.primaryDelta < 0) {
                setState(() {
                  _expanded = true;  
                });
              } else {
                setState(() {
                  _expanded = false; 
                });
              }
             }),
        ),
      )
    ]));