Flutter: Condition jsonData is List<dynamic> failing

Question

I am trying to fetch data from a table named Collections in a local MySql database. The Code is as under:

class CollectionsPage extends StatefulWidget {
  @override
  _CollectionsPageState createState() => _CollectionsPageState();
}

class _CollectionsPageState extends State<CollectionsPage> {
  Future<List<dynamic>> fetchData() async {
    final response = await http.get(Uri.parse('http://10.0.2.2/myDashFolder/collections_fetch.php'));
    if (response.statusCode == 200) {
      try {
        final jsonData = jsonDecode(response.body);
        print(response.body);
        if (jsonData is List<dynamic>) {
          print(response.body);
          return jsonData;
        }
      } catch (e) {
        print('Failed to decode JSON: $e');
      }
    }
    return [];
  }
  @override
  Widget build(BuildContext context) {
    return FutureBuilder<List<dynamic>>(
        future: fetchData(),
    builder: (context, snapshot) {
    if (snapshot.connectionState == ConnectionState.waiting) {
       return Center(
       child: CircularProgressIndicator(),
       );
    } else if (snapshot.hasError) {
       return Text('Error: ${snapshot.error}');
    } else if (snapshot.hasData) {
        return Flexible(
          fit: FlexFit.loose,
          child:ListView.builder(
            itemCount: snapshot.data!.length,
            itemBuilder: (context, index) {
            final collection = snapshot.data![index];
            return ListTile(
              title: Text(collection['ProjectName'] ?? ''),
              subtitle: Text(collection['TransactionDate'] ?? ''),
            );
            },
      )
      );
    } else {
      return Text('No data available');
    }
    },
    );
  }
}

The first print statement works but the second doesn't. Please help me solve this.

I was trying to show the fethced data but nothing is displayed on the screen.

Answer 1

Your response print(response.body); is most likely not a valid list of maps of strings.

With a hardcoded valid response like the following it works as expected:

final jsonData = jsonDecode("[{\"ProjectName\" : \"first\", \"TransactionDate\" : \"1\"}]");

In relation to your latest comment with an example result of

{"status":"success" ,"result":[
{"Id":"2","TransactionDate":"2020-11-02","ProjectName":"Rove","FromName":"Tejaswi","ToName":"Amita","Amount":"100000","Narration":"Given to Amita"},
{"Id":"3","TransactionDate":"2020-11-02","ProjectName":"Rove","FromName":"Amita","ToName":"Others","Amount":"100000","Narration":"Murram filling through Shakti Vellimaran"}
]}

you receive a Map<String, dynamic> instead where you probably want to access the "result" list. So you have to change your if to:

       if (jsonData is Map<String, dynamic> && jsonData["result"] is List<dynamic>) {
          final List<dynamic> result = jsonData["result"] as List<dynamic>;
          print(result);
          return result;
        }