如何使用 gmail api 发送 https://www.googleapis.com/auth/gmail.send 使用邮件程序在 flutter 上发送电子邮件

问：

scope(['https://mail.google.com/']);它可以正常工作，但谷歌建议使用scopes: ['email', 'https://www.googleapis.com/auth/gmail.send']);

要使用 Gmail API 并继续验证过程，您需要从 SMTP 协议中迁移出来。相反，应使用 https://www.googleapis.com/auth/gmail.send 范围。此范围仍为您的项目提供足够的访问权限以正常工作。

如果您的应用仅使用 SMTP 协议，请注意，仅将广泛访问 https://mail.google.com/ 范围用于使用 SMTP 协议发送电子邮件会违反最小范围策略。要使用 Gmail API 并继续执行验证过程，您需要迁移出 SMTP 协议，并改用敏感 https://www.googleapis.com/auth/gmail.send 范围。

pubspec.yaml

dependencies:

  mailer: ^6.0.0
  firebase_core: ^2.9.0
  firebase_auth: ^4.4.0
  google_sign_in: ^5.0.0

sendMail（）

Future<void> sendEmail() async {

    SmtpServer? smtpServer;

    try {
      // Setting up Google SignIn
      final googleSignIn = GoogleSignIn.standard(
          scopes: ['email', 'https://www.googleapis.com/auth/gmail.send']);
      
      // Signing in
      final account = await googleSignIn.signIn();

      if (account == null) {
        // User didn't authorize
        return;
      }

      final auth = await account.authentication;

      // Creating SMTP server from the access token
      smtpServer = gmailSaslXoauth2(account.email,auth.accessToken!);
    } on PlatformException catch (e) {
      print(e);
    }

    final message = Message()
      ..from = Address('[email protected]', 'Your name')
      ..recipients.add('[email protected]')
      ..subject = 'Test Dart Mailer library'
      ..text = 'This is the plain text.\nThis is line 2 of the text part.'
      ..html = "<h1>Test</h1>\n<p>Hey! Here's some HTML content</p>";

    // Ready to send a message now
    final sendReport = await send(message, smtpServer!);
  }

未处理的异常：身份验证失败（代码：334）

[ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: Authentication Failed (code: 334), response:
< eyJzdGF0dXMiOiI0MDAiLCJzY2hlbWVzIjoiQmVhcmVyIiwic2NvcGUiOiJodHRwczovL21haWwuZ29vZ2xlLmNvbS8ifQ==
#0      _doAuthentication (package:mailer/src/smtp/smtp_client.dart:106:5)
<asynchronous suspension>
#1      connect (package:mailer/src/smtp/smtp_client.dart:136:5)
<asynchronous suspension>
#2      send (package:mailer/src/smtp/mail_sender.dart:93:20)
<asynchronous suspension>
#3      _MyHomePageState.sendEmail (package:send_mail/main.dart:102:24)
<asynchronous suspension>