How to stop a widget to reload on setState() method in StatefulWidget Class in Flutter

Question

What I am trying to achieve is to save the state of the Widget i.e it should not refresh when the setState() method is been called.

class _GenderSelectionPageState extends State<GenderSelectionPage> {
  bool isFemaleSelected = false;
  AdmobBannerSize bannerSize;
  GlobalKey _globalKey = new GlobalKey();

  bool isLoaded = false;

  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    bannerSize = AdmobBannerSize.BANNER;
  }

  @override
  Widget build(BuildContext context) {
    double height = MediaQuery.of(context).size.height;
    double width = MediaQuery.of(context).size.width;

    return new Scaffold(
      body: new Container(
          width: width,
          child: new Center(
            child: Column(
              mainAxisAlignment: MainAxisAlignment.end,
              children: <Widget>[
                Expanded(
                  child: Column(
                    mainAxisAlignment: MainAxisAlignment.center,
                    mainAxisSize: MainAxisSize.max,
                    children: <Widget>[
                      Flexible(
                        child: new Hero(
                          tag: "gender",
                          child: Material(
                            child: new Row(
                              children: <Widget>[
                                InkWell(
                                  onTap: () {
                                    setState(() {
                                      if (isFemaleSelected) {
                                        isFemaleSelected = false;
                                      } else {
                                        isFemaleSelected = true;
                                      }
                                    });
                                  },
                                  child: Opacity(
                                    child: Image.asset(
                                      "assets/woman.png",
                                      height: height / 4,
                                      width: width / 2 - 12,
                                    ),
                                    opacity: isFemaleSelected ? 1.0 : 0.30,
                                  ),
                                ),
                                InkWell(
                                  onTap: () {
                                    setState(() {
                                      if (isFemaleSelected) {
                                        isFemaleSelected = false;
                                      } else {
                                        isFemaleSelected = true;
                                      }
                                    });
                                  },
                                  child: Opacity(
                                    opacity: !isFemaleSelected ? 1.0 : 0.30,
                                    child: Image.asset(
                                      "assets/boy.png",
                                      height: height / 4,
                                      width: width / 2 - 12,
                                    ),
                                  ),
                                ),
                              ],
                            ),
                          ),
                        ),
                      ),
                    ],
                  ),
                  flex: 1,
                ),
                InkWell(
                    onTap: () {
                      setState(() {

                      });
                      Navigator.push(
                          context,
                          MaterialPageRoute(
                              builder: (BuildContext) =>
                                  new HeightWeightSelection(isFemaleSelected
                                      ? "assets/woman.png"
                                      : "assets/boy.png")));
                    },
                    child: Container(
                      margin: EdgeInsets.only(bottom: 12.0),
                      child: new Image.asset(
                        "assets/next.png",
                        height: 64.0,
                        width: 64.0,
                      ),
                    )),
                new AdmobBannerWrapper(adUnitId: getBannerAdUnitId(),adSize: bannerSize,key: _globalKey,),
               /* new AdmobBanner(
                  adUnitId: getBannerAdUnitId(),
                  adSize: bannerSize,
                  listener:
                      (AdmobAdEvent event, Map<String, dynamic> args) {
                    handleEvent(event, args, 'Banner');
                  },
                ),*/
              ],
            ),
          )),
    );
  }

I don't want to call the AdmobBannerWrapper every time I press my image button at the bottom.AdmobBannerWrapper should be loaded once only but the thing is whenever I click the Next Image it load AdmobBannerWrapper method every time.

Leonoreleonsis

if you don't want to rebuild the AdmobBannerWrapper again,then move that widget into the parent widget. – Nikko

Thanks Darish but my parent widget is Column wrapped in Scaffold of the Statefull Class. – Leonoreleonsis

it is not clear why you want to keep the AdmobBannerWrapper in the child widget. Could you please explain your use case? – Nikko

Wait I will upload my whole class so you can better understand it. – Leonoreleonsis

(adUnitId: getBannerAdUnitId() don't do that. You may want to read #52250078 – Auxesis

Answer 1

Build it in initState() then use it's reference wherever required it will not build again until parent widget reinitialized.

  var banner;

  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    bannerSize = AdmobBannerSize.BANNER;
    banner = AdmobBannerWrapper(adUnitId: getBannerAdUnitId(),adSize: bannerSize,key:_globalKey,);
  }

than call it in by reference here banner

  @override
  Widget build(BuildContext context) {
    double height = MediaQuery.of(context).size.height;
    double width = MediaQuery.of(context).size.width;

    return new Scaffold(
      body: new Container(
          width: width,
          child: new Center(
            child: Column(
              mainAxisAlignment: MainAxisAlignment.end,
              children: <Widget>[
                Expanded(
                  child: Column(
                    mainAxisAlignment: MainAxisAlignment.center,
                    mainAxisSize: MainAxisSize.max,
                    children: <Widget>[
                      Flexible(
                        child: new Hero(
                          tag: "gender",
                          child: Material(
                            child: new Row(
                              children: <Widget>[
                                InkWell(
                                  onTap: () {
                                    setState(() {
                                      if (isFemaleSelected) {
                                        isFemaleSelected = false;
                                      } else {
                                        isFemaleSelected = true;
                                      }
                                    });
                                  },
                                  child: Opacity(
                                    child: Image.asset(
                                      "assets/woman.png",
                                      height: height / 4,
                                      width: width / 2 - 12,
                                    ),
                                    opacity: isFemaleSelected ? 1.0 : 0.30,
                                  ),
                                ),
                                InkWell(
                                  onTap: () {
                                    setState(() {
                                      if (isFemaleSelected) {
                                        isFemaleSelected = false;
                                      } else {
                                        isFemaleSelected = true;
                                      }
                                    });
                                  },
                                  child: Opacity(
                                    opacity: !isFemaleSelected ? 1.0 : 0.30,
                                    child: Image.asset(
                                      "assets/boy.png",
                                      height: height / 4,
                                      width: width / 2 - 12,
                                    ),
                                  ),
                                ),
                              ],
                            ),
                          ),
                        ),
                      ),
                    ],
                  ),
                  flex: 1,
                ),
                InkWell(
                    onTap: () {
                      setState(() {

                      });
                      Navigator.push(
                          context,
                          MaterialPageRoute(
                              builder: (BuildContext) =>
                                  new HeightWeightSelection(isFemaleSelected
                                      ? "assets/woman.png"
                                      : "assets/boy.png")));
                    },
                    child: Container(
                      margin: EdgeInsets.only(bottom: 12.0),
                      child: new Image.asset(
                        "assets/next.png",
                        height: 64.0,
                        width: 64.0,
                      ),
                    )),
                banner, /*this is our variable */
               /* new AdmobBanner(
                  adUnitId: getBannerAdUnitId(),
                  adSize: bannerSize,
                  listener:
                      (AdmobAdEvent event, Map<String, dynamic> args) {
                    handleEvent(event, args, 'Banner');
                  },
                ),*/
              ],
            ),
          )),
    );
  }

Bunker

Yes did the same for now. Thanks :) – Leonoreleonsis

Any idea about how to use keys to achieve this? – Leonoreleonsis

Keys won't be of help here once parent widget build it by default rebuild children with it. – Bunker

You are the real hero !!! Thank you so much. It litterally save my life – Veloz

Best approach!... Works very fine. Thank you so much for this answer – Matronymic

perfect answer. – Haworth

Answer 2

Put it inside a stateless widget:

class AdBanner extends StatelessWidget{
  final adUnitId;
  final adSize;

  const AdBanner({Key key, this.adUnitId, this.adSize}) : super(key: key);

  Widget build(BuildContext context){
    return AdmobBannerWrapper(
      adUnitId: getBannerAdUnitId(),
      adSize: bannerSize,
      key: _globalKey,
      );
  }
}

next time when you call setState if the parameters are unchanged, it is not going to get rebuilt.

Polenta

Can this stateless widget be called as part of stateful widget build widget tree hierarchy ?? – Recompense