Question

我正在一个单独的文件中制作一个show对话框函数，然后将其调用到另一个文件中，向函数提供4个参数，包括BuildContext参数，如图所示

void showDialogSingleButton(BuildContext context, String title, String 
message, String buttonLabel) {


showDialog(
  context: context,
  builder: (BuildContext context) {
  return AlertDialog(
    title:
    new Text(title),
    content:
    new Text(message),
    actions: <Widget>[
      new FlatButton(
        child:
        new Text(buttonLabel),
        onPressed: () {
          Navigator.
          of(context).pop();
        },
      ),
    ],
   );
  },
 );
}

并在此文件中将其称为将来的对象，作为显示对话框功能：

Future launchURL(String url) async {

if(await canLaunch(url)) {

  await launch(url, forceSafariVC: true, forceWebView: true);
}
else {
  showDialogSingleButton( context, "Unable to reach your website.", 
"Currently unable to reach the website $URL. Please try again at a later 
time.", "OK");
 }
}

当我调用该方法时，由于某种原因，它给了我这个错误：

  Compiler message:
  lib/screens/login/login_page.dart:45:31: Error: Getter not found: 
  'context'.
  showDialogSingleButton( context, "Unable to reach your website.", 
  "Currently unable to reach the website $URL. Please try again at a 
  later 
  time.", "OK");
                          ^^^^^^^
  lib/screens/login/login_page.dart:45:31: Error: The getter 'context' 
  isn't defined for the class 'LoginScreen'.
  - 'LoginScreen' is from 
  'package:gam3ity_aa/screens/login/login_page.dart' 
  ('lib/screens/login/login_page.dart').
  Try correcting the name to the name of an existing getter, or defining 
   a getter or field named 'context'.
  showDialogSingleButton( context, "Unable to reach your website.", 
  "Currently unable to reach the website $URL. Please try again at a 
  later 
  time.", "OK");

Answer 1

在您的launchUrl函数中，context可能不存在，如果不看更多代码就很难说出来。

一种继续调试的好方法是将BuildContext作为参数添加到函数launchUrl中。无论如何，您都应该这样做，launchUrl不应只是更好地，更易于维护的代码来引用类级别的变量，以使函数需要引用的每个变量都明确。

Future launchURL(String url) async {

if(await canLaunch(url)) {

  await launch(url, forceSafariVC: true, forceWebView: true);
}
else {
  //HERE, DOES CONTEXT EXIST??
  showDialogSingleButton( context, "Unable to reach your website.", 
"Currently unable to reach the website $URL. Please try again at a later 
time.", "OK");
 }
}

未为该类定义构建上下文

1 个答案: