原型Dart页

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import  'package:flutter/material.dart' ;   class BoldText extends StatelessWidget {   @ override //override 的方法 build   Widget build(BuildContext context) {     // TODO: implement build     throw UnimplementedError();   }   }

　　

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import 'package:flutter/material.dart'; class testname extends StatelessWidget{   @override //override 的方法 build   Widget build(BuildContext context) {     // TODO: implement build     //throw UnimplementedError();     return null;   } }

　　

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import 'package:flutter/material.dart'; class testname extends StatelessWidget{   @override //override 的方法 build,实现对应的 Widget,返回的 Widget 来替换 null 即可   Widget build(BuildContext context) {     // TODO: implement build     //throw UnimplementedError();     return null;   } }

　　静态Widget 

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import 'package:flutter/material.dart';   class BoldText extends StatelessWidget {     @override   Widget build(BuildContext context) {     return _buildWidget();   }     Widget _buildWidget() {     return Text(       'Hello, world!',       textDirection: TextDirection.ltr,       textAlign: TextAlign.center,       overflow: TextOverflow.ellipsis,       style: TextStyle(fontWeight: FontWeight.bold),     );   }   }

　　动态Widget 

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import 'package:flutter/material.dart';   class BoldText extends StatelessWidget {   final String data;   BoldText(this.data);   @override   Widget build(BuildContext context) {     return _buildWidget();   }     Widget _buildWidget() {     return Text(       //'Hello, world!',       data,       textDirection: TextDirection.ltr,       textAlign: TextAlign.center,       overflow: TextOverflow.ellipsis,       style: TextStyle(fontWeight: FontWeight.bold),     );   }   }