调用notifyListeners()时，对话框状态未更新

Question

我正在使用提供程序来管理我的flutter应用程序中的状态。我有一个对话，最初应该显示CircularProgressBar，然后再显示一些内容。当我需要CircularProgressBar更改内容时，我会调用notifyListeners((，但这似乎没有任何作用。这是我的一些代码，如果你还需要看，请告诉我。

被调用以显示对话的方法：

displayDialog() {
return showDialog(
context: context,
barrierDismissible: false,
builder: (BuildContext context) {
return ChangeNotifierProvider<CreateAccountProvider>(
builder: (_) => CreateAccountProvider(),
child: CreateNewUserDialog(),
);
},
);
}
final createAccountButton = Material(
elevation: 5.0,
color: Colors.lightGreen,
child: MaterialButton(
minWidth: MediaQuery.of(context).size.width,
padding: EdgeInsets.fromLTRB(20.0, 15.0, 20.0, 15.0),
onPressed: () {
createAccountProvider.createAccountClicked(context);
displayDialog();
},
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Icon(
Icons.play_arrow,
color: Colors.white,
),
SizedBox(
width: 5,
),
Text(
"Create an account",
textAlign: TextAlign.center,
style: TextStyle(color: Colors.white),
),
],
),
),
);

提供商中的相关代码：

// initial values for loading and loadingMessage
bool loading = false;
String loadingMessage;
void createAccountClicked(BuildContext context) {
print("Create account clicked");
validateAllFields();
if (name != null &&
email != null &&
password != null &&
confirmPassword != null) {
loading = true;
loadingMessage = "Creating new user";
notifyListeners(); // <- nothing happens when this is called :(
RestEndpoints.createNewUser(name, email, password, confirmPassword, "on")
.then(createUserSuccess, onError: createUserError);
}
}
void createUserSuccess(response) {
print(response.data);
if (response.data["status"] == "OK") {
loading = false;
notifyListeners();
}
}
void createUserError(error) {
loading = false;
print("Error creating new user: ${error.toString()}");
notifyListeners();
}

对话框的相关位：

@override
Widget build(BuildContext context) {
final createAccountProvider = Provider.of<CreateAccountProvider>(context);
// ...
return AlertDialog(
content: Column(
mainAxisSize: MainAxisSize.min,
children: <Widget>[
Visibility(
visible: createAccountProvider.loading, //<-- this is never visible
child: Loading(createAccountProvider.loadingMessage),
),
Visibility(
visible: !createAccountProvider.loading, //<-- this is always visible
child: SingleChildScrollView(
child: Column(
children: <Widget>[
SizedBox(height: 30),
title,
SizedBox(height: 30),
subText,
SizedBox(height: 30),
confirmCodeTextField,
SizedBox(height: 50),
infoBox,
newVerificationCode,
continueButton
],
),
),
),
],
),
);
}

问题：当调用notifyListeners((时，如何更新我的对话？

Answer 1

此行之后：

notifyListeners(); // <- nothing happens when this is called :(

您有一条线路可能会立即调用loading = false;：

RestEndpoints.createNewUser(name, email, password, confirmPassword, "on")
.then(createUserSuccess, onError: createUserError);

可能您有某种错误，因此可能会立即调用createUserError，从而在此处设置loading = false;：

void createUserError(error) {
loading = false;
print("Error creating new user: ${error.toString()}");
notifyListeners();
}

尝试在没有以下行的情况下运行代码：

RestEndpoints.createNewUser(name, email, password, confirmPassword, "on")
.then(createUserSuccess, onError: createUserError);