dart - 颤振代码，接受来自用户显示必填字段的值

Question

**你好，我正在开发一个应用程序，用户应该在其中输入整数值。根据这些值，我们应该显示这些文本字段的数量..

• 例如：

            1) enter total number of subject=10;
            2) click on the button;
            3) After button is clicked should display 10 text fields;
            4) I have no idea what to do so if you know then help me plz.**
  

  导入“包：颤振/material.dart”；

  class imcaaddsubject extends StatefulWidget {
    @override
    _imcaaddsubjectState createState() => _imcaaddsubjectState();
  }
  
  class _imcaaddsubjectState extends State<imcaaddsubject> {
    @override
    Widget build(BuildContext context) {
      return Container(
        padding: EdgeInsets.all(5),
        child: Card(
          child: ListView(
            padding: EdgeInsets.all(10),
            children: <Widget>[
              Padding(
                padding: EdgeInsets.only(top: 10),
              ),
              new TextField(
                decoration: InputDecoration(
                  border: OutlineInputBorder(
                      borderSide: BorderSide(style: BorderStyle.solid)),
                  labelText: "NUMBER OF SUBJECTS",
                  hintText: "Enter number of subjects",
                ),keyboardType: TextInputType.number,
              ),
              Padding(
                padding: EdgeInsets.only(top: 15),
              ),
              new RaisedButton(
                child: Text(
                  "OK",
                  style:
                      TextStyle(color: Colors.white, fontWeight: FontWeight.bold),
                ),
                color: Colors.cyan,
                onPressed: () {},
              )
            ],
          ),
        ),
      );
    }
  }
  

标签： dartflutter

Answer 1

你可以这样尝试：

import 'package:flutter/material.dart';

void main() => runApp(MaterialApp(
      home: MyApp(),
    ));

class MyApp extends StatefulWidget {
  @override
  MyAppState createState() => MyAppState();
}

class MyAppState extends State<MyApp> {
  int numberOfSubjects = 0;

  Widget subjectsBuilder(int numberOfSubjects) {
    if (numberOfSubjects > 0) {
      return ListView.builder(
        itemBuilder: (BuildContext context, numberOfSubjects) {
          return TextField(
            decoration: InputDecoration(hintText: "enter a text"),
          );
        },
        itemCount: numberOfSubjects,
      );
    } else {
      return SizedBox();
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Column(children: <Widget>[
        Expanded(
          child: Container(
            padding: EdgeInsets.all(5),
            child: Card(
              child: ListView(
                padding: EdgeInsets.all(10),
                children: <Widget>[
                  Padding(
                    padding: EdgeInsets.only(top: 10),
                  ),
                  new TextField(
                    onSubmitted: (String value) {
                      setState(() {
                        numberOfSubjects = int.parse(value);
                      });
                    },
                    decoration: InputDecoration(
                      border: OutlineInputBorder(
                          borderSide: BorderSide(style: BorderStyle.solid)),
                      labelText: "NUMBER OF SUBJECTS",
                      hintText: "Enter number of subjects",
                    ),
                    keyboardType: TextInputType.number,
                  ),
                  Padding(
                    padding: EdgeInsets.only(top: 15),
                  ),
                ],
              ),
            ),
          ),
        ),
        Expanded(
          child: subjectsBuilder(numberOfSubjects),
        )
      ]),
    );
  }
}

此代码将根据用户输入在第一个文本字段下方显示多个文本字段，当然您可以在新页面中呈现它..您也不必使用按钮，用户提交文本就足够了。