NestedScrollView issue, throwing error when switching between two screens

I was using extendBody : true, inside scaffold and was getting the same error. On removing it the error got resolved.

Just add key: UniqueKey() to NestedScrollView.

your code will be

child: NestedScrollView(
  key: UniqueKey()
  controller: _controller,
  headerSliverBuilder: (BuildContext context, bool innerBoxIsScrolled) {
    return <Widget>[
      SliverAppBar(
        automaticallyImplyLeading: false,
        pinned: true,
        expandedHeight: 140.0,
        floating: false,
        centerTitle: true,
        flexibleSpace: FlexibleSpaceBar(
          centerTitle: true,
          background: new Container(
            child: FutureBuilder(
              future: CoverImagesApi().getImageFile(1),
              builder: (context, snapshot) {
                if(snapshot.data != null) {
                  return Container(
                    child: Column(
                      children: <Widget>[
                        Expanded(
                          flex: 5,
                          child: Container(
                            alignment: Alignment.topCenter,
                          ),
                        ),
                        Expanded(
                          flex: 2,
                          child: new Container(
                            child: Center(
                            child: Text('Obecná tabuľa',
                              style: TextStyle(
                                fontSize: 26.0,
                                fontWeight: FontWeight.bold
                              ),
                              textAlign: TextAlign.center,
                            ),
                            ),
                            decoration: BoxDecoration(
                              color: Color.fromRGBO(255, 255, 255, 0.8)
                            ),
                            alignment: Alignment.bottomCenter, //variable above
                          )
                        ),
                      ],
                    ),
                    decoration: new BoxDecoration(
                      image: new DecorationImage(
                        fit: BoxFit.cover
                        image: snapshot.data.existsSync() ? Image.file(snapshot.data).image : AssetImage('assets/tabula.jpg'),
                      ),
                    ),
                  );
                } else {
                  return Container(height: 0.0, width: 0.0);
                }
              }
            ),
          ),
        ),
      ),
    ];

  },
  body: DataFiller(scaffoldKey: _scaffoldKey),
)

There is no problem in that, just a hot-restart is good to fix the problem. This is because hot-reload doesn't change the state of the app and you did an action that draws from state that isn't there(It assumes it's there)..

If all else fail, try cleaning your app and that should be good

I have TabView with 4 tabs. In 2 of them I had ScrollController for ListView but 2 other didn't have ScrollController but had Grid. What helped me was adding ScrollController to those Grids. Maybe this advice will help someone just add ScrollController where they are missing.