使用AsyncTask进行发送邮件与附件

使用AsyncTask发送邮件和附件的步骤如下：

1. 在AndroidManifest.xml文件中添加权限：

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

2. 创建一个类继承自AsyncTask，用于在后台线程执行邮件发送操作。

public class SendMailTask extends AsyncTask<Void, Void, Boolean> {

    private Context mContext;
    private String mRecipient;
    private String mSubject;
    private String mBody;
    private ArrayList<String> mAttachments;

    public SendMailTask(Context context, String recipient, String subject, String body, ArrayList<String> attachments) {
        mContext = context;
        mRecipient = recipient;
        mSubject = subject;
        mBody = body;
        mAttachments = attachments;
    }

    @Override
    protected Boolean doInBackground(Void... params) {
        try {
            // 创建一个邮件对象
            MimeMessage message = new MimeMessage(Session.getDefaultInstance(new Properties()));
            // 设置发件人
            message.setFrom(new InternetAddress("你的邮箱地址"));
            // 设置收件人
            message.addRecipient(Message.RecipientType.TO, new InternetAddress(mRecipient));
            // 设置主题
            message.setSubject(mSubject);
            // 创建一个MimeMultipart对象用于存放邮件的各个部分
            MimeMultipart multipart = new MimeMultipart();
            // 创建一个MimeBodyPart对象用于存放邮件正文
            MimeBodyPart bodyPart = new MimeBodyPart();
            // 设置邮件正文内容和格式
            bodyPart.setContent(mBody, "text/html;charset=utf-8");
            // 将邮件正文部分添加到MimeMultipart对象中
            multipart.addBodyPart(bodyPart);
            // 添加附件
            if (mAttachments != null && mAttachments.size() > 0) {
                for (String attachment : mAttachments) {
                    // 创建一个MimeBodyPart对象用于存放附件
                    MimeBodyPart attachmentPart = new MimeBodyPart();
                    // 读取附件文件
                    File file = new File(attachment);
                    // 将附件添加到MimeBodyPart对象中
                    attachmentPart.attachFile(file);
                    // 将附件部分添加到MimeMultipart对象中
                    multipart.addBodyPart(attachmentPart);
                }
            }
            // 将MimeMultipart对象设置为邮件内容
            message.setContent(multipart);
            // 发送邮件
            Transport.send(message, "你的邮箱地址", "你的邮箱密码");
            return true;
        } catch (Exception e) {
            e.printStackTrace();
            return false;
        }
    }

    @Override
    protected void onPostExecute(Boolean result) {
        super.onPostExecute(result);
        if (result) {
            Toast.makeText(mContext, "邮件发送成功！", Toast.LENGTH_SHORT).show();
        } else {
            Toast.makeText(mContext, "邮件发送失败！", Toast.LENGTH_SHORT).show();
        }
    }
}

3. 在Activity中调用SendMailTask并传入相应的参数。

public class MainActivity extends AppCompatActivity {

    private Button mSendButton;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mSendButton = findViewById(R.id.send_button);
        mSendButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // 收件人地址
                String recipient = "收件人地址";
                // 邮件主题
                String subject = "邮件主题";
                // 邮件正文
                String body = "邮件正文";
                // 附件列表
                ArrayList<String> attachments = new ArrayList<>();
                attachments.add("/sdcard/attachment1.jpg");
                attachments.add("/sdcard/attachment2.docx");
                // 发送邮件
                new SendMailTask(MainActivity.this, recipient, subject, body, attachments).execute();
            }
        });
    }
}