Passing data from parent to child StatefulWidget Flutter

Question

Hellow, Im newbie in flutter..please help me to pass data from parent to child statefullwidget.. then..send to API..

This is my code

class Home extends StatefulWidget {
  final String user; // I will passing this into getCategory()
  final String email;

  Home(this.user, this.email);

  @override
  HomeState createState() => HomeState();
}

class HomeState extends State<Home> {
  CategoryList listCategory = CategoryList();

  void getCategory() async {
    var json = await ApiCategoryList().getCategoryList(widget.user); //not working ..
    setState(() {
      listCategory = CategoryList.fromJson(json);
    });
  }

  @override
  void initState() {
    super.initState();
    this.getCategory();
  }

@override
  Widget build(BuildContext context) {
   return ListTile(data from API here)
}

Thanks for helping me..regards

Solution

Your problem has nothing to do with passing the data to the child widget. Except that you probably can't call the values from initState. The problem is you are accessing it probably before it is loaded.

To solve this there is a Widget called FutureBuilder. Here is how to use it:

instead of return ListTile(data from API here) use

return FutureBuilder(
      future: getCategory(),
      builder: (BuildContext context, AsyncSnapshot snapshot) {
        if (snapshot.connectionState == ConnectionState.done) {
          return //Here the listTile
        }
          return //Here what should be displayed while loading
                 //I would recommend CircularProgressIndicator();
        }
)

The Futurebuilder executes a function and waits until it is finished, then it builds the desired widgets. For this to work, the getCategory function must be edited. Since the function is now called from the FutureBuider, you may no longer execute it from the initState.

  CategoryList listCategory = CategoryList(); //Delete

  Future<CategoryList> getCategory() async {
    CategoryList listCategory = CategoryList();
    // Get data from api:
    // ....

    //pass data to listCatergory:
    listCategory = CategoryList.fromJson(json);
    
    // return
    return listCategory 
   
  }

When you will acces data in the FutureBuilder you will have to use:

snapshot.theDataYouWant

e.g.

Text(
 snapshot.theDataYouWant
),

Comments

[Afridi Kayal]

You can get the widget instance in your stateful widget class using the widget getter. Use widget.user / widget.email, etc.

[Nan Di]

@AfridiKayal yap i know that,i mean..i will put user into void function..look on getCategory function..widget.user not working there

[m123]

Will you access the api after a button press or in the initial build

[Nan Di]

@M123 actually the code is start from press button login..then I sent 2 param user and email into statefull widget.. at the same time , i will make ListView -- ListTile based on data API.

[Afridi Kayal]

What kind of problem are you getting when using widget.user?

[Nan Di]

@AfridiKayal .."A [State] object's configuration is not corresponding [StatefulWidget] instance. "

[m123]

If your question is solved, don't forget to mark it as solved and if it has helped you, give it an up-vote.

[Nan Di]

Iet me try this