我在main.dart中有一个AppBar，我想将它定义为主要的子项，但是我想更改AppBar本身的标题，当我在子页面时，我怎样才能正确地做到这一点？voidmain()=>runApp(MyApp());classMyAppextendsStatelessWidget{@overrideWidgetbuild(BuildContextcontext){returnMaterialApp(title:"FlutterApp",theme:ThemeData(primaryColor:Colors.cyan,brightness:Brightness.dark),home:Scaffol
我不确定为什么在dependencies下的pubspec.yaml文件中有一个大写符号。见下图。即使没有上限符号，该项目也能正常运行。 最佳答案 这叫做caretsyntax:Caretsyntaxprovidesamorecompactwayofexpressingthemostcommonsortofversionconstraint.^versionmeans"therangeofallversionsguaranteedtobebackwardscompatiblewiththespecifiedversion",andf
我不确定为什么在dependencies下的pubspec.yaml文件中有一个大写符号。见下图。即使没有上限符号，该项目也能正常运行。 最佳答案 这叫做caretsyntax:Caretsyntaxprovidesamorecompactwayofexpressingthemostcommonsortofversionconstraint.^versionmeans"therangeofallversionsguaranteedtobebackwardscompatiblewiththespecifiedversion",andf
我想在flutter中将File转换为ByteData对象。像这样:import'dart:io';Filefile=getSomeCorrectFile();//ThisfileiscorrectByteDatabytes=ByteData(file.readAsBytesSync());//Doesntcompilereturnbytes;我知道ByteData构造函数接收字节数量的长度并用0初始化它们，所以我可以做类似ByteData(file.readAsBytesStync().length);但是我该如何填充它们呢？我错过了什么？ 最佳答案
我想在flutter中将File转换为ByteData对象。像这样:import'dart:io';Filefile=getSomeCorrectFile();//ThisfileiscorrectByteDatabytes=ByteData(file.readAsBytesSync());//Doesntcompilereturnbytes;我知道ByteData构造函数接收字节数量的长度并用0初始化它们，所以我可以做类似ByteData(file.readAsBytesStync().length);但是我该如何填充它们呢？我错过了什么？ 最佳答案
如何在initState中访问Provider的上下文一直报错flutter:ThefollowingassertionwasthrownbuildingBuilder:flutter:inheritFromWidgetOfExactType(_Provider)orinheritFromElement()wascalledbeforeflutter:_ProductDetailsPageState.initState()completed.每当我运行下面的代码时if(Provider.of(context).selectedProduct==null){product=Product
如何在initState中访问Provider的上下文一直报错flutter:ThefollowingassertionwasthrownbuildingBuilder:flutter:inheritFromWidgetOfExactType(_Provider)orinheritFromElement()wascalledbeforeflutter:_ProductDetailsPageState.initState()completed.每当我运行下面的代码时if(Provider.of(context).selectedProduct==null){product=Product
我在androidstudio中运行flutter代码时遇到异常。I/flutter(5360):══╡EXCEPTIONCAUGHTBYWIDGETSLIBRARY╞═══════════════════════════════════════════════════════════I/flutter(5360):ThefollowingassertionwasthrownbuildingText("xyz"):I/flutter(5360):NoDirectionalitywidgetfound.I/flutter(5360):RichTextwidgetsrequireaDire
我在androidstudio中运行flutter代码时遇到异常。I/flutter(5360):══╡EXCEPTIONCAUGHTBYWIDGETSLIBRARY╞═══════════════════════════════════════════════════════════I/flutter(5360):ThefollowingassertionwasthrownbuildingText("xyz"):I/flutter(5360):NoDirectionalitywidgetfound.I/flutter(5360):RichTextwidgetsrequireaDire
我怎样才能使底部FAB像下图一样？这是我当前的代码示例:class_ItemDetailsStateextendsState{@overrideWidgetbuild(BuildContextcontext){doubleheight=MediaQuery.of(context).size.height*0.42;returnScaffold(body:Stack(children:[CustomScrollView(slivers:[...],),Positioned(bottom:0,child:FloatingActionButton(elevation:4,onPressed:
