Question

我试图添加一个BottomModelSheet在交易列表中添加新的交易，我遵循，这就是我得到的错误，我在这里错过了什么？

这是我的main.dart文件

import 'package:expense_tracker/widgets/transaction_list.dart';

import './widgets/transaction_list.dart';
import 'package:flutter/material.dart';
import './widgets/new_transaction.dart';
import './models/transaction.dart';

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

class MyHomePage extends StatefulWidget {
  // String titleInput;
  // String amountInput;

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

class _MyHomePageState extends State<MyHomePage> {
  final titleController = TextEditingController();

  final amountController = TextEditingController();

  final List<Transaction> _userTransactions = [
    Transaction(
      id: 't1',
      title: 'New Shoes',
      amount: 1000,
      date: DateTime.now(),
    ),
    Transaction(
      id: 't2',
      title: 'USB Cable',
      amount: 600,
      date: DateTime.now(),
    ),
  ];

  void _addNewTransaction(String txTitle, double txAmount) {
    final newTX = Transaction(
        title: txTitle,
        amount: txAmount,
        date: DateTime.now(),
        id: DateTime.now().toString());

    setState(() {
      _userTransactions.add(newTX);
    });
  }

  void _startAddNewTransaction(BuildContext ctx) {
    showModalBottomSheet(context: ctx,builder: (bCtx) {
      return NewTransaction(_addNewTransaction);
    });
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Flutter App'),
          actions: [
            IconButton(
              icon: Icon(Icons.add),
              onPressed: () => _startAddNewTransaction(context),
            ),
          ],
        ),
        body: SingleChildScrollView(
          child: Column(
              // mainAxisAlignment: MainAxisAlignment.start,
              crossAxisAlignment: CrossAxisAlignment.stretch,
              children: <Widget>[
                Container(
                  width: double.infinity,
                  child: Card(
                    color: Colors.blue,
                    child: Text('CHART'),
                    elevation: 10,
                  ),
                ),
                TransactionList(_userTransactions),
              ]),
        ),
        floatingActionButtonLocation: FloatingActionButtonLocation.endFloat,
        floatingActionButton: FloatingActionButton(
          child: Icon(Icons.add),
          onPressed: () => _startAddNewTransaction(context),
        ),
      ),
    );
  }
}

单击appBar上的图标和底部的floatActionButton时，将显示相同的BottomModalSheet，但它们都不起作用。

Answer 1

您要传递给BuildContext方法的_startAddNewTransaction是_MyHomePageState的方法。由于_MyHomePageState包含MaterialApp（并非相反），因此它的BuildContext对此一无所知。

您有2个选择：

使用Builder小部件包装调用该方法的小部件，小部件的BuildContext将了解MaterialApp
创建一个新的小部件（例如MyHomePageContent），并将其传递给物料应用的body:参数。

第一个选项是快速修复，第二个选项是更好的解决方法。

将项目分成多个文件是一个好主意，例如：

main.dart

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

my_app.dart

class MyApp extends StatelessWidget {
    @override
    Widget build(BuildContext context) {
      return MaterialApp(
        home: MyHomePage(),
      );
    }
}

my_home_page.dart

class MyHomePage extends StatefulWidget {
  // String titleInput;
  // String amountInput;

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

class _MyHomePageState extends State<MyHomePage> {
  final titleController = TextEditingController();

  final amountController = TextEditingController();

  final List<Transaction> _userTransactions = [
    Transaction(
      id: 't1',
      title: 'New Shoes',
      amount: 1000,
      date: DateTime.now(),
    ),
    Transaction(
      id: 't2',
      title: 'USB Cable',
      amount: 600,
      date: DateTime.now(),
    ),
  ];

  void _addNewTransaction(String txTitle, double txAmount) {
    final newTX = Transaction(
        title: txTitle,
        amount: txAmount,
        date: DateTime.now(),
        id: DateTime.now().toString());

    setState(() {
      _userTransactions.add(newTX);
    });
  }

  void _startAddNewTransaction(BuildContext ctx) {
    showModalBottomSheet(
        context: ctx,
        builder: (bCtx) {
          return NewTransaction(_addNewTransaction);
        });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Flutter App'),
        actions: [
          IconButton(
            icon: Icon(Icons.add),
            onPressed: () => _startAddNewTransaction(context),
          ),
        ],
      ),
      body: SingleChildScrollView(
        child: Column(
            // mainAxisAlignment: MainAxisAlignment.start,
            crossAxisAlignment: CrossAxisAlignment.stretch,
            children: <Widget>[
              Container(
                width: double.infinity,
                child: Card(
                  color: Colors.blue,
                  child: Text('CHART'),
                  elevation: 10,
                ),
              ),
              TransactionList(_userTransactions),
            ]),
      ),
      floatingActionButtonLocation: FloatingActionButtonLocation.endFloat,
      floatingActionButton: FloatingActionButton(
        child: Icon(Icons.add),
        onPressed: () => _startAddNewTransaction(context),
      ),
    );
  }
}

手势引起的异常未找到MediaQuery窗口小部件。 MyHomePage小部件需要MediaQuery小部件祖先

1 个答案: