我试着用@Vinayak B提交的代码。然而，我得到一个错误说:没有提供smtp

我在这里创建了一个新问题，提供了更多信息

我终于自己修好了。我得用另一个邮件罐 我必须确保我的“不太安全的应用程序访问权限”被打开。

我希望这能帮助那些有同样问题的人。这样做后，这段代码也可以在谷歌玻璃上工作。

我无法运行维纳亚克B的代码。最后我解决了这个问题如下:

1.使用这个

2.使用AsyncTask。

3.更改发件人gmail帐户的安全问题。(更改为“TURN ON”)

package io.formics.tourguide

import android.annotation.SuppressLint
import android.content.Intent
import android.net.Credentials
import android.net.Uri
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.util.Log
import android.widget.Toast
import kotlinx.android.synthetic.main.activity_feedback.*
import org.jetbrains.annotations.Async
import java.lang.Exception

import java.util.Properties;


import javax.activation.DataHandler;
import javax.activation.FileDataSource
import javax.mail.*
import javax.mail.internet.*


class FeedbackActivity : AppCompatActivity()  {
  
    val props = Properties()


    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_feedback)

        props.put("mail.smtp.auth", "true");
        props.put("mail.smtp.starttls.enable", "true");
        props.put("mail.smtp.host", "smtp.gmail.com");
        props.put("mail.smtp.port", "587");

        btnSendEmail.setOnClickListener {
            Thread {
                try {
                    sendEmail()
                    // Your implementation
                } catch (ex: Exception) {
                    ex.printStackTrace()
                }
            }.start()


        }
    }


    private fun sendEmail() {



        try {

            val session = Session.getInstance(props,
                object : javax.mail.Authenticator() {
                    //Authenticating the password
                    override fun getPasswordAuthentication(): javax.mail.PasswordAuthentication {
                        return PasswordAuthentication("abc@xyz.com", "password")
                    }
                })

            val message = MimeMessage(session);
            message.setFrom(InternetAddress("abc@xyz.com"));
            message.setRecipients(
                Message.RecipientType.TO,
                InternetAddress.parse(editCC.text.toString())
            )
            message.subject = editSubject.text.toString()
            message.setText(
                "Dear Mail Crawler,"
                        + "\n\n No spam to my email, please!"
            );

            //val messageBodyPart = MimeBodyPart();

            //val multipart = MimeMultipart();

            //val file = "path of file to be attached";

//            val fileName = "attachmentName"
           // val source = FileDataSource(file);
            //messageBodyPart.setDataHandler(DataHandler(source));
            //messageBodyPart.setFileName(fileName);
            //multipart.addBodyPart(messageBodyPart);

            //message.setContent(multipart);

            Transport.send(message);
            System.out.println("Done");



        } catch (e: MessagingException) {
            throw  RuntimeException(e);
        }

           }
}




 

谢谢你提供的宝贵信息。代码运行正常。我也可以通过添加以下代码添加附件。

private Multipart _multipart; 
_multipart = new MimeMultipart(); 

public void addAttachment(String filename,String subject) throws Exception { 
    BodyPart messageBodyPart = new MimeBodyPart(); 
    DataSource source = new FileDataSource(filename); 
    messageBodyPart.setDataHandler(new DataHandler(source)); 
    messageBodyPart.setFileName(filename); 
    _multipart.addBodyPart(messageBodyPart);

    BodyPart messageBodyPart2 = new MimeBodyPart(); 
    messageBodyPart2.setText(subject); 

    _multipart.addBodyPart(messageBodyPart2); 
} 



message.setContent(_multipart);

我为其他需要帮助的人找到了一个更短的选择。代码是:

package com.example.mail;

import java.util.Properties;

import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;

public class SendMailTLS {

    public static void main(String[] args) {

        final String username = "username@gmail.com";
        final String password = "password";

        Properties props = new Properties();
        props.put("mail.smtp.auth", "true");
        props.put("mail.smtp.starttls.enable", "true");
        props.put("mail.smtp.host", "smtp.gmail.com");
        props.put("mail.smtp.port", "587");

        Session session = Session.getInstance(props,
          new javax.mail.Authenticator() {
            protected PasswordAuthentication getPasswordAuthentication() {
                return new PasswordAuthentication(username, password);
            }
          });

        try {

            Message message = new MimeMessage(session);
            message.setFrom(new InternetAddress("from-email@gmail.com"));
            message.setRecipients(Message.RecipientType.TO,
                InternetAddress.parse("to-email@gmail.com"));
            message.setSubject("Testing Subject");
            message.setText("Dear Mail Crawler,"
                + "\n\n No spam to my email, please!");

            Transport.send(message);

            System.out.println("Done");

        } catch (MessagingException e) {
            throw new RuntimeException(e);
        }
    }
}

来源:通过JavaMail API发送电子邮件

希望这能有所帮助!好运！

那些正在获得ClassDefNotFoundError的人尝试移动这三个jar文件到你的项目的lib文件夹，它为我工作!!