android - 布局边界未在 Flutter 应用程序中显示，但它显示在其他应用程序中

Question

我刚开始使用 Flutter 并使用默认配置创建了一个空白应用程序，当我从开发人员选项中打开显示布局边界时，它没有像任何其他应用程序那样显示任何边界。

这是怎么回事？

Answer 1

要在 Flutter 应用的开发者选项中显示布局边界，我们必须这样做

1. 在 main.dart 类中导入这个包。

   import '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:这是我的完整类(class)

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),
      ),
    );
  }
}