我有类似的东西.我很难理解这个错误.
为什么在这里访问filterController会出现此错误？但是如果我在构建方法中移动当前的整个TextFormField创建(在注释A和B之间),它不会出现此错误？如何在构建方法中移动整个TextFormField使filterController成为静态然后解决此问题？
为什么在这里访问filterController会出现此错误？但是如果我在构建方法中移动当前的整个TextFormField创建(在注释A和B之间),它不会出现此错误？如何在构建方法中移动整个TextFormField使filterController成为静态然后解决此问题？
class AppHomeState extends State<AppHome> with SingleTickerProviderStateMixin
{
TabController _tabController;
final filterController = new TextEditingController(text: "Search");
//----A
TextFormField email = new TextFormField(
keyboardType: TextInputType.emailAddress,controller: filterController,------>ERROR : Error: Only static members can be accessed in initializers
);
//----B
@override
Widget build(BuildContext context)
{
return new Scaffold(
appBar: new AppBar(..),);
}
}
我该如何解决这个问题？
解决方法
class AppHomeState extends State<AppHome> with SingleTickerProviderStateMixin {
TabController _tabController;
final filterController = new TextEditingController(text: "Search");
TextFormField email = ...
…是一个初始化程序,此时无法访问它.
初始化器在构造函数之前执行,但只有在完成对超级构造函数(在您的示例中隐式)的调用之后才允许访问它.
因此,只有在构造函数体(或更高版本)中才允许访问它.
这就是您收到错误消息的原因：
controller: filterController,
访问this.filterController(如果你不明确地写它,这是隐式的).
要解决您的问题(假设电子邮件需要最终),您可以使用工厂构造函数和构造函数初始化列表：
class AppHomeState extends State<AppHome> with SingleTickerProviderStateMixin {
factory SingleTickerProviderStateMixin() =>
new SingleTickerProviderStateMixin._(new TextEditingController(text: "Search"));
SingleTickerProviderStateMixin._(TextEditingController textEditingController) :
this.filterController = textEditingController,this.email = new TextFormField(
keyboardType: TextInputType.emailAddress,controller: textEditingController);
TabController _tabController;
final filterController;
final TextFormField email;
或者当电子邮件字段不需要是最终电子邮件时,可以在构造函数初始化列表中初始化：
class AppHomeState extends State<AppHome> with SingleTickerProviderStateMixin {
SingleTickerProviderStateMixin() {
email = new TextFormField(
keyboardType: TextInputType.emailAddress,);
}
TabController _tabController;
final filterController = new TextEditingController(text: "Search");
TextFormField email;
但是在Flutter小部件中,initState通常用于此
class AppHomeState extends State<AppHome> with SingleTickerProviderStateMixin {
@override
void initState() {
super.initState();
email = new TextFormField(
keyboardType: TextInputType.emailAddress,);
}
TabController _tabController;
final filterController = new TextEditingController(text: "Search");
TextFormField email;
