Java.lang.NoClassDefFoundError - JavaMail

Question

我的主要活动中有一个线程，它将创建类的对象 SendMail

package Logic;

import java.util.Date;
import java.util.Properties;

import javax.activation.DataHandler;
import javax.activation.FileDataSource;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.Multipart;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.AddressException;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeBodyPart;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimeMultipart;

import android.util.Log;

public class SendMail {

String from;
String to;
String subject;
String bodyText;
String fileName;

public SendMail(String to, String fileName, String PCN) {

    this.to = to;
    this.fileName = fileName;
    this.from = "Hello@gmail.com";
    this.bodyText = "FILE";
    this.subject = PCN;
}

public void sendMailWithAttatchment() {

    Properties properties = new Properties();
    properties.put("mail.smtp.host", "IP_ADDRESS");
    properties.put("mail.smtp.port", "25");
    Session session = Session.getDefaultInstance(properties, null);

    MimeMessage message = new MimeMessage(session);

    try {

        message.setFrom(new InternetAddress(from));

        message.setRecipient(Message.RecipientType.TO, new InternetAddress(
                to));
        message.setSubject(subject);
        message.setSentDate(new Date());

        MimeBodyPart messagePart = new MimeBodyPart();
        messagePart.setText(bodyText);

        MimeBodyPart attachmentPart = new MimeBodyPart();

        FileDataSource fileDataSource = new FileDataSource(fileName) {
            @Override
            public String getContentType() {
                return "application/octet-stream";

            }
        };

        attachmentPart.setDataHandler(new DataHandler(fileDataSource));
        attachmentPart.setFileName(fileDataSource.getName());

        Multipart multipart = new MimeMultipart();
        multipart.addBodyPart(messagePart);
        multipart.addBodyPart(attachmentPart);
        message.setContent(multipart);
        Transport.send(message);
    } catch (AddressException e) {
        Log.e("ADDRESS_EXCEPTION: ", e.getMessage());
    } catch (MessagingException e) {
        Log.e("MESSAGING_EXCEPTION: ", e.getMessage());
    }
}

}

但是编译器抛出一个异常说： Java.lang.NoClassDefFoundError. javax.activation.Datahandler

我读过这个线程：NoClassDefFoundError - Eclipse 和 Android并且.jar files javamail.jar和javax.activation.jar位于我的libs文件夹下，但是即使我清理了项目，这也会引发异常。

有任何想法吗？

这些是抛出的异常：

08-07 10:19:49.870: E/AndroidRuntime(17736): java.lang.NoClassDefFoundError: javax.activation.DataHandler
08-07 10:19:49.870: E/AndroidRuntime(17736):    at javax.mail.internet.MimeBodyPart.setContent(MimeBodyPart.java:647)
08-07 10:19:49.870: E/AndroidRuntime(17736):    at javax.mail.internet.MimeBodyPart.setText(MimeBodyPart.java:892)
08-07 10:19:49.870: E/AndroidRuntime(17736):    at javax.mail.internet.MimeBodyPart.setText(MimeBodyPart.java:680)
08-07 10:19:49.870: E/AndroidRuntime(17736):    at javax.mail.internet.MimeBodyPart.setText(MimeBodyPart.java:668)
08-07 10:19:49.870: E/AndroidRuntime(17736):    at sendMailWithAttatchment(SendMail.java:56)
08-07 10:19:49.870: E/AndroidRuntime(17736):    at sendMailWithAttatchment(SendMail.java:56)
08-07 10:19:49.870: E/AndroidRuntime(17736):    at CreateNistFile(MyActivity.java:530)

Answer 1

java 为 android 的 javaMail 引入新方法：

你只需要在gradle中添加这几行：

 android {
     packagingOptions {
         pickFirst 'META-INF/LICENSE.txt' // picks the JavaMail license file
     }
 }

 repositories { 
     jcenter()
     maven {
         url "https://maven.java.net/content/groups/public/"
     }
 }

 dependencies {
     compile 'com.sun.mail:android-mail:1.5.5'
     compile 'com.sun.mail:android-activation:1.5.5'
 }

并像您一样发送 smtp 邮件...祝您好运。

Answer 2

是的，这是因为您的 .jar 文件未正确导入。只要遵循我现有的答案，它肯定会对您有所帮助。并且，下面的快照很重要（它通知附加的 jar 文件应该如下图所示）-

重要的是，每当您遇到Java.lang.NoClassDefFoundError异常时，上面的一个就是解决该问题的解决方案。