value displayed after hot reload but null after click

Question

I want to retrieve data from json, after click (form another file), I get null for all values ($tgl, $dokter, $paket, etc), but when I hot-reload (at this below codes) the results are there and are corrects.

what's wrong with my codes ?

class DetilTreatment extends StatefulWidget{
  final String nomtri;
  final String jenis;
  DetilTreatment(this.nomtri,this.jenis);
  @override
    State<StatefulWidget> createState() {
      return DetilTreatmentState();
    }
}

class DetilTreatmentState extends State<DetilTreatment>{
  String urldest='json_detail_rawat_dart.php';
  String tgl,dokter,paket,keterangan;
  List tindakan,terapis;

  @override
  void initState() {
    super.initState();
    loadData();
  }

  void loadData() async { 
    final response = await http.get(remoteURL + urldest + '?nomtri=${widget.nomtri}');
    if (response.statusCode == 200) {
      List<dynamic> isi = jsonDecode(response.body);
      tgl = isi[0]['tgl']; 
      dokter = isi[0]['dokter'];  
      paket = isi[0]['paket'];
      keterangan = isi[0]['keterangan'];
    } else {
      throw Exception('Gagal Ambil Data Perawatan');
    }
  }

  @override
    Widget build(BuildContext context) {
      return new Scaffold(
        backgroundColor: Colors.blue[50],
        appBar: new AppBar(
          title: const Text('Data Riwayat Perawatan'),
        ),
        body: ListView(
          padding: EdgeInsets.all(15.0),
          children: <Widget>[
            // all results are null, but when hot-reload the results displayed !
            Text('Tgl/Jam : $tgl', textAlign: TextAlign.left), 
            Text('Nama Dokter : $dokter', textAlign: TextAlign.left),
            Text('Paket : $paket', textAlign: TextAlign.left),
            Text('Treatment : ', textAlign: TextAlign.left),
            Text('Keterangan : $keterangan', textAlign: TextAlign.left),
          ],
        )
        );
    }
}

Solution 1

call SetState() inside your method, and maybe you will get a null error inside build, so its better add one CircularProgressIndicator,

    bool isLoading=false;
         @override
              void initState() {
                super.initState();
                loadData();
              }

              void loadData() async { 
                final response = await http.get(remoteURL + urldest + '?nomtri=${widget.nomtri}');
                if (response.statusCode == 200) {
                 setState(() {
            tgl = isi[0]['tgl']; 
            dokter = isi[0]['dokter'];  
            paket = isi[0]['paket'];
            keterangan = isi[0]['keterangan'];
            isLoading=true;
          });
                } else {
                  throw Exception('Gagal Ambil Data Perawatan');
                }
              }

Widget build(BuildContext context){
if(!isLoading)
{
return Center(child:CircularProgressIndicator());
}
else {retur Container();}

Solution 2

You need to call setState() to cause Flutter to re-render when state changes.

  void loadData() async { 
    final response = await http.get(remoteURL + urldest + '?nomtri=${widget.nomtri}');
    if (response.statusCode == 200) {
      List<dynamic> isi = jsonDecode(response.body);

      setState(() {
        tgl = isi[0]['tgl']; 
        dokter = isi[0]['dokter'];  
        paket = isi[0]['paket'];
        keterangan = isi[0]['keterangan'];
      });
    } else {
      throw Exception('Gagal Ambil Data Perawatan');
    }
  }

Comments

[M. Syamsul Arifin]

yes, it's work, but I must clicked 2x from source link

[M. Syamsul Arifin]

thank you very much, it's work well ! but sorry I cannot click this as usefull answer, because my reputation is low :D

[Günter Zöchbauer]

"I must clicked 2x from source link" sorry, but I don't understand what you mean? What is "source link"?

[M. Syamsul Arifin]

sorry with my english, I mean that widget displayed after I clicked from another file. this is code : onTap: () { Navigator.of(context).push(new MaterialPageRoute<Null>( builder: (BuildContext context) { return new DetilTreatment(treatment[index]['nomtri'],treatment[index]['‌​jenis']); }, fullscreenDialog: true) ); }, so, first click onTap -> null, second click -> correct value. thank you for your help

[Günter Zöchbauer]

I don't see why you would need to click twice, except if you run into the error satish soni mentioned in the other answer.

[M. Syamsul Arifin]

I only add CircularProgressIndicator() at build, like @satish soni answer below, and it's work

[Günter Zöchbauer]

Ok, so if that fixes your problem then you should accept his answer.