布局范围未在Fultter应用程序中显示，但在其他应用程序中显示

Question

我只是从Flutter开始，并使用默认配置创建了一个空白应用，当我打开开发人员选项的显示布局范围时，它没有像其他任何应用一样显示任何边界。

这是怎么回事？

Answer 1

要显示Flutter应用程序开发人员选项的布局范围，我们必须这样做

1. 将此包导入main.dart类。

   导入'package：flutter / rendering.dart';

2. 在build（）或main（）中，您必须将此“ debugPaintSizeEnabled”变量设置为true。

   debugPaintSizeEnabled = true;
   

示例：这是我的完整课程

import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';

void main()
{
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.

  @override
  Widget build(BuildContext context) {
    debugPaintSizeEnabled = true;
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(    
        primarySwatch: Colors.blue,
      ),
    home: MyHomePage(title: 'Flutter Demo Home Page'),

    );
  }
}
class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);
  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(

          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.display1,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }
}