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Java Mail API using GMAIL OAuth API in Android

Java Mail API using GMAIL OAuth API in Android
Hello friends, In this post, I will show how to send mail with GMail using OAuth2.0 in Android. This Project contains a lot of steps like Permission, Google Play Service check to do.
So, please download the project to perform GMail API completely.

First of All, we have to generate OAuth key in Google API Console. To Generate OAuth Key, use your SHA1 key and your app's Package Name as in your Manifest.Paste Following code in your Command Prompt to get SHA1 key in Windows
keytool -list -v -keystore "%USERPROFILE%\.android\debug.keystore" -alias androiddebugkey -storepass android -keypass android

Project Structure

Create a new Project in Android Studio with the required Specifications.

AndroidManifest.xml

Don't forget to add the following permission in your manifest file.
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.GET_ACCOUNTS"/>
<!--Added for Accessing External Storage-->
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
We have to add the following Jar Files into your Project as like Normal Java Mail API.
  1. mail.jar
  2. activation.jar
  3. additionnal.jar
Download Jars From Server

build.gradle

Open your app level build.gradle file add the following lines.
dependencies {
    compile fileTree(include: ['*.jar'], dir: 'libs')
    testCompile 'junit:junit:4.12'
    compile 'com.android.support:appcompat-v7:23.3.0'
    compile 'com.android.support:design:23.3.0'
    compile 'com.google.android.gms:play-services-identity:8.4.0'
    compile('com.google.api-client:google-api-client-android:1.22.0') {
        exclude group: 'org.apache.httpcomponents'
    }
    compile('com.google.apis:google-api-services-gmail:v1-rev44-1.22.0') {
        exclude group: 'org.apache.httpcomponents'
    }
    compile files('libs/mail.jar')
    compile files('libs/activation.jar')
    compile files('libs/additionnal.jar')
}
Initialize the Google API Client as in the following.
GoogleAccountCredential mCredential;
String[] SCOPES = {
    GmailScopes.GMAIL_LABELS,
    GmailScopes.GMAIL_COMPOSE,
    GmailScopes.GMAIL_INSERT,
    GmailScopes.GMAIL_MODIFY,
    GmailScopes.GMAIL_READONLY,
    GmailScopes.MAIL_GOOGLE_COM
};
// Initialize credentials and service object.
mCredential = GoogleAccountCredential.usingOAuth2(
  getApplicationContext(), Arrays.asList(SCOPES))
  .setBackOff(new ExponentialBackOff());
Following line is used to start Account Pick in Android
// Start a dialog from which the user can choose an account
startActivityForResult(mCredential.newChooseAccountIntent(), Utils.REQUEST_ACCOUNT_PICKER);
Use the following code to generate and initialize all the processes regarding this project.
// Async Task for sending Mail using GMail OAuth
    private class MakeRequestTask extends AsyncTask {
        private com.google.api.services.gmail.Gmail mService = null;
        private Exception mLastError = null;
        private View view = sendFabButton;

        public MakeRequestTask(GoogleAccountCredential credential) {
            HttpTransport transport = AndroidHttp.newCompatibleTransport();
            JsonFactory jsonFactory = JacksonFactory.getDefaultInstance();
            mService = new com.google.api.services.gmail.Gmail.Builder(
                    transport, jsonFactory, credential)
                    .setApplicationName(getResources().getString(R.string.app_name))
                    .build();
        }

        @Override
        protected String doInBackground(Void... params) {
            try {
                return getDataFromApi();
            } catch (Exception e) {
                mLastError = e;
                cancel(true);
                return null;
            }
        }

        private String getDataFromApi() throws IOException {
            // getting Values for to Address, from Address, Subject and Body
            String user = "me";
            String to = Utils.getString(edtToAddress);
            String from = mCredential.getSelectedAccountName();
            String subject = Utils.getString(edtSubject);
            String body = Utils.getString(edtMessage);
            MimeMessage mimeMessage;
            String response = "";
            try {
                mimeMessage = createEmail(to, from, subject, body);
                response = sendMessage(mService, user, mimeMessage);
            } catch (MessagingException e) {
                e.printStackTrace();
            }
            return response;
        }

        // Method to send email
        private String sendMessage(Gmail service,
                                   String userId,
                                   MimeMessage email)
                throws MessagingException, IOException {
            Message message = createMessageWithEmail(email);
            // GMail's official method to send email with oauth2.0
            message = service.users().messages().send(userId, message).execute();

            System.out.println("Message id: " + message.getId());
            System.out.println(message.toPrettyString());
            return message.getId();
        }

        // Method to create email Params
        private MimeMessage createEmail(String to,
                                        String from,
                                        String subject,
                                        String bodyText) throws MessagingException {
            Properties props = new Properties();
            Session session = Session.getDefaultInstance(props, null);

            MimeMessage email = new MimeMessage(session);
            InternetAddress tAddress = new InternetAddress(to);
            InternetAddress fAddress = new InternetAddress(from);

            email.setFrom(fAddress);
            email.addRecipient(javax.mail.Message.RecipientType.TO, tAddress);
            email.setSubject(subject);

            // Create Multipart object and add MimeBodyPart objects to this object
            Multipart multipart = new MimeMultipart();

            // Changed for adding attachment and text
            // This line is used for sending only text messages through mail
            // email.setText(bodyText);

            BodyPart textBody = new MimeBodyPart();
            textBody.setText(bodyText);
            multipart.addBodyPart(textBody);

            if (!(activity.fileName.equals(""))) {
                // Create new MimeBodyPart object and set DataHandler object to this object
                MimeBodyPart attachmentBody = new MimeBodyPart();
                String filename = activity.fileName; // change accordingly
                DataSource source = new FileDataSource(filename);
                attachmentBody.setDataHandler(new DataHandler(source));
                attachmentBody.setFileName(filename);
                multipart.addBodyPart(attachmentBody);
            }

            // Set the multipart object to the message object
            email.setContent(multipart);
            return email;
        }

        private Message createMessageWithEmail(MimeMessage email)
                throws MessagingException, IOException {
            ByteArrayOutputStream bytes = new ByteArrayOutputStream();
            email.writeTo(bytes);
            String encodedEmail = Base64.encodeBase64URLSafeString(bytes.toByteArray());
            Message message = new Message();
            message.setRaw(encodedEmail);
            return message;
        }

        @Override
        protected void onPreExecute() {
            mProgress.show();
        }

        @Override
        protected void onPostExecute(String output) {
            mProgress.hide();
            if (output == null || output.length() == 0) {
                showMessage(view, "No results returned.");
            } else {
                showMessage(view, output);
            }
        }

        @Override
        protected void onCancelled() {
            mProgress.hide();
            if (mLastError != null) {
                if (mLastError instanceof GooglePlayServicesAvailabilityIOException) {
                    showGooglePlayServicesAvailabilityErrorDialog(
                            ((GooglePlayServicesAvailabilityIOException) mLastError)
                                    .getConnectionStatusCode());
                } else if (mLastError instanceof UserRecoverableAuthIOException) {
                    startActivityForResult(
                            ((UserRecoverableAuthIOException) mLastError).getIntent(),
                            Utils.REQUEST_AUTHORIZATION);
                } else {
                    showMessage(view, "The following error occurred:\n" + mLastError.getMessage());
                    Log.v("Error", mLastError.getMessage());
                }
            } else {
                showMessage(view, "Request Cancelled.");
            }
        }
    }

Screens:

Screen1
Screen2
Screen3
Screen4
Screen5

Important

You should add the following lines in proguard while releasing your APK
-keep class com.google.** 
Thanks to Kaba Droid42 for this.

Download Source Code

You can download the full source from the following Github link. If you Like this library, Please star it in Github.