I was trying to make a button that adds new widget to my screen . I'm putting my Builder inside an Expanded widget and a FloatingactionButton below that called the method _addCardWidget() This is my Statefull screen :

/* Import */

class ajouterUnDocument extends StatefulWidget {
  @override
  State<ajouterUnDocument> createState() => _ajouterUnDocumentState();
}



final GlobalKey<FormState> _formKey = GlobalKey<FormState>();

class _ajouterUnDocumentState extends State<ajouterUnDocument> {
  List<Widget> _cardList = [(InputRefNomProduit()), (InputRefNomProduit())];

  void _addCardWidget() {
    setState(() {
      _cardList.add(InputRefNomProduit());

      _cardList.add(InputQuntitePrixProduit());
    });
  }

    @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Color(0xFF2A2D3E),
      body: Form(
        key: _formKey,
        child: Card(
          shadowColor: Color.fromARGB(255, 255, 255, 255),
          color: Color(0xFF2A2D3E),
          shape:
              RoundedRectangleBorder(borderRadius: BorderRadius.circular(40.0)),
          elevation: 10.0,
          child: Container(
            width: 1800,
            child: Column(
              children: <Widget>[
                Center(
                  child: Container(
                    padding: EdgeInsets.all(20),
                    child: Column(
                      children: <Widget>[
                        Text(
                          "AJOUTER UN DOCUMENT",
                          style: TextStyle(
                              fontSize: 30, fontWeight: FontWeight.bold),
                        ),
                        Divider(
                          thickness: 3,
                        ),

                        Row(
                          mainAxisSize: MainAxisSize.max,
                          children: [
                            Expanded(
                              child: Column(
                                children: [
                                  SizedBox(height: 20.0),    
                                  ListView.builder(
                                      itemCount: _cardList.length,
                                      itemBuilder: (context, index) {
                                        return _cardList[index];
                                      }),

                                  SizedBox(height: 20.0),

                                  
                                ],
                              ),
                            ),
                          Row(
                          children: <Widget>[
                            SizedBox(
                              width: 370.0,
                            ),
                            MaterialButton(
                              color: Colors.grey[200],
                              onPressed: () {},
                              child: Text(
                                "Annuler",
                                style: TextStyle(color: Colors.black),
                              ),
                            ),
                            SizedBox(
                              width: 20.0,
                            ),
                            MaterialButton(
                              color: Color.fromARGB(255, 75, 100, 211),
                              onPressed: () {
                                _addCardWidget();
                              },
                              child: Text(
                                "Ajouter une nouvelle ligne",
                                style: TextStyle(color: Colors.white),
                              ),
                            ),
                            SizedBox(
                              width: 20.0,
                            ),
                            
                                  );
                                }
                              },
                             
                            ),
                          ],
                        ),
                      ],
                    ),
                  ),
                ),
              ],
            ),
          ),
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _addCardWidget,
        tooltip: 'Add',
        child: Icon(Icons.add),
      ),
    );
  }
}

Now , all i'm getting is a blank screen and my Debug Console is showing these error :

`Scaffold
lib\…\Screen\ajouterunDct.dart:61
════════════════════════════════════════════════════════════════════════════════

════════ Exception caught by rendering library ═════════════════════════════════
Assertion failed:
D:\…\rendering\box.dart:1982
hasSize
"RenderBox was not laid out: RenderPhysicalShape#6d64a relayoutBoundary=up8"

The relevant error-causing widget was
Card
lib\…\Screen\ajouterunDct.dart:65
═════`
Assertion failed:
D:\…\rendering\box.dart:1982
hasSize
"RenderBox was not laid out: RenderSemanticsAnnotations#95d37 relayoutBoundary=up6 NEEDS-PAINT"

The relevant error-causing widget was
Scaffold
lib\…\Screen\ajouterunDct.dart:61
════════════════════════════════════════════════════════════════════════════════

CodePudding user response：

Wrap the form with SafeArea() then it should display unter the noth of the phone. Or wrap the Form with Expanded()

CodePudding user response：

Surround your listview.builder with expanded widget and add the flex property of the expanded widget to 1. This will solve the problem with the listview.

CodePudding user response：

Wrap it inside the Container or Sized box, Assign certain height and it should work!