为什么我的RaisedButton在Flutter中不起作用？

问题描述

我一直在Flutter中开发待办事项列表应用程序，但是在此过程中，我意识到应该在添加新任务时添加按钮不起作用。我不知道为什么它不起作用，因为我对Flutter很陌生。为什么会出现此问题！？

main.dart

  List<String> _toDoItems = [];

  void _addToDoItem(String task) {
    if(task.length > 0) {
      setState(() {  
        _toDoItems.add(task);
      });
    }
  }
  Expanded(
    flex: 8,child: TextField(
      autofocus: true,onSubmitted: (val) {
        _addToDoItem(val);
      },),Expanded(
    flex: 2,child: RaisedButton(
        child: Text('ADD'),onPressed: () => _addToDoItem,

解决方法

您可以在下面复制粘贴运行完整代码
您可以使用TextEditingController并将controller.text传递给_addToDoItem
代码段

TextEditingController _controller = TextEditingController();

Expanded(
      flex: 8,child: TextField(
        controller: _controller,Expanded(
      flex: 2,child: RaisedButton(
        child: Text('ADD'),onPressed: () => _addToDoItem(_controller.text),

工作演示

完整代码

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

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

class MyAppState extends State<MyApp> {
  List<String> _toDoItems = [];
  TextEditingController _controller = TextEditingController();

  void _addToDoItem(String task) {
    if (task.length > 0) {
      setState(() {
        _toDoItems.add(task);
      });
    }
  }

  Widget _buildToDoItem(String toDoText) {
    return ListTile(title: Text(toDoText));
  }

  Widget _buildToDoList() {
    return Expanded(
      child: ListView.builder(
        itemBuilder: (context,index) {
          if (index < _toDoItems.length) {
            return _buildToDoItem(_toDoItems[index]);
          }
        },),);
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: PreferredSize(
            preferredSize: Size.fromHeight(50),child: AppBar(
              centerTitle: true,backgroundColor: Colors.red,title: Text(
                'To Do List',style: TextStyle(
                  fontSize: 24,fontWeight: FontWeight.bold,)),backgroundColor: Colors.white,body: Column(
          crossAxisAlignment: CrossAxisAlignment.center,children: [
            Container(
                margin: EdgeInsets.all(22),child: Row(
                  children: [
                    Expanded(
                      flex: 8,child: TextField(
                        controller: _controller,autofocus: true,onSubmitted: (val) {
                          _addToDoItem(val);
                        },decoration: InputDecoration(
                          hintText: 'Add a tak here...',enabledBorder: OutlineInputBorder(
                            borderRadius:
                                BorderRadius.all(Radius.circular(12.0)),borderSide: BorderSide(color: Colors.red,width: 2),focusedBorder: OutlineInputBorder(
                            borderRadius:
                                BorderRadius.all(Radius.circular(12.0)),borderSide:
                                BorderSide(color: Colors.red,width: 1.5),Expanded(
                      flex: 2,child: RaisedButton(
                        child: Text('ADD'),)
                  ],_buildToDoList(),],);
  }
}

,

您没有添加参数。

import json

dictionary = {"team1" : team1,"team2": team2,"ht": ht,"ft": ft}

json_dump = json.dumps(dictionary)

with open("YourFilePath","w") as f:
    f.write(json_dump)