参数类型'Set<String>'不能分配给参数类型"映射<字符串，字符串>

Question

我正试图在Flutter应用程序中使用Auth0创建一个用户身份验证系统。Auth0REST文档给出了一个cURL的例子，但我没有找到任何能够完成cURL工作的flutter包。所以，我使用了http。这是代码：

Future<String> getToken(String userId) async {
final response = await http.post(
Uri.parse('https://my-auth0-subdomain.auth0.com/oauth/token'),  // I used my real subdomain
body: jsonEncode({
'grant_type=client_credentials',
'client_id=my_project_client_id',  // I used my real client id
'client_secret=my_project_client_secret',  // I used my real client secret
'audience=https://my-auth0-subdomain.auth0.com/api/v2/'  // I used my real subdomain
}),
headers: {
'content-type: application/x-www-form-urlencoded'
},
);
final token = jsonDecode(response.body)["access_token"];
return token;
}

这给了我一个错误，即第10行的The argument type 'Set<String>' can't be assigned to the parameter type 'Map<String, String>'.(headers: {...}(
我可以使用headers: {'content-type': 'application/x-www-form-urlencoded'},解决此错误
但这会导致Auth0{"error":"access_denied","error_description":"Unauthorized"}出现错误。API设置正确，因为在运行时

curl --request POST 
--url 'https://my-auth0-subdomain.auth0.com/oauth/token' 
--header "content-type: application/x-www-form-urlencoded" 
--data grant_type=client_credentials 
--data 'client_id=my_project_client_id' 
--data client_secret=my_project_client_secret 
--data 'audience=https://my-auth0-subdomain.auth0.com/api/v2/'

它返回一个"access_token"、"scope"、"expires_in"和"token_type"

请帮忙。这很重要。
提前感谢：(

Answer 1

尝试将数据发送为使用编码的url

Map<String, String> myBody= {
'grant_type' : 'client_credentials',
'client_id' : 'my_project_client_id',  // I used my real client id
'client_secret' : 'my_project_client_secret',  // I used my real client secret
'audience ' : 'https://my-auth0-subdomain.auth0.com/api/v2/'  // I used my real subdomain     
};
Future<String> getToken(String userId) async {
final response = await http.post(
Uri.parse('https://my-auth0-subdomain.auth0.com/oauth/token'),  // I used my real subdomain
body: myBody,
headers: {
'content-type: application/x-www-form-urlencoded'
},
);
final token = jsonDecode(response.body)["access_token"];
return token;
}