//...........................................
body: FutureBuilder<String>(
        future: fetchJoke(),
        builder: (BuildContext context, AsyncSnapshot<String> snapshot) {
          switch (snapshot.connectionState) {
            case ConnectionState.none:
            case ConnectionState.active:
            case ConnectionState.waiting:
              return Center(child: CircularProgressIndicator());
            case ConnectionState.done:
              return Center(
                child: Text(snapshot.hasError ? snapshot.error : snapshot.data,
                    style: TextStyle(fontSize: 22.0)),
              );
          }
        },
      ),
//...........................................