SyncAdapter

/**
 * Define a sync adapter for the app.
 * <p/>
 * <p>This class is instantiated in {@link SyncService}, which also binds SyncAdapter to the system.
 * SyncAdapter should only be initialized in SyncService, never anywhere else.
 * <p/>
 * <p>The system calls onPerformSync() via an RPC call through the IBinder object supplied by
 * SyncService.
 */
class SyncAdapter extends AbstractThreadedSyncAdapter {
    /**
     * Constructor. Obtains handle to content resolver for later use.
     */
    public SyncAdapter(Context context, boolean autoInitialize) {
        super(context, autoInitialize);
    }

    /**
     * Constructor. Obtains handle to content resolver for later use.
     */
    public SyncAdapter(Context context, boolean autoInitialize, boolean allowParallelSyncs) {
        super(context, autoInitialize, allowParallelSyncs);
    }

    @Override
    public void onPerformSync(Account account, Bundle extras, String authority,
                              ContentProviderClient provider, SyncResult syncResult) {
        //Jobs you want to perform in background.
        Log.e("" + account.name, "Sync Start");
    }

}

Sync Service

/**
 * Define a Service that returns an IBinder for the
 * sync adapter class, allowing the sync adapter framework to call
 * onPerformSync().
 */
public class SyncService extends Service {
    // Storage for an instance of the sync adapter
    private static SyncAdapter sSyncAdapter = null;
    // Object to use as a thread-safe lock
    private static final Object sSyncAdapterLock = new Object();

    /*
     * Instantiate the sync adapter object.
     */
    @Override
    public void onCreate() {
        /*
         * Create the sync adapter as a singleton.
         * Set the sync adapter as syncable
         * Disallow parallel syncs
         */
        synchronized (sSyncAdapterLock) {
            if (sSyncAdapter == null) {
                sSyncAdapter = new SyncAdapter(getApplicationContext(), true);
            }
        }
    }

    /**
     * Return an object that allows the system to invoke
     * the sync adapter.
     */
    @Override
    public IBinder onBind(Intent intent) {
        /*
         * Get the object that allows external processes
         * to call onPerformSync(). The object is created
         * in the base class code when the SyncAdapter
         * constructors call super()
         */
        return sSyncAdapter.getSyncAdapterBinder();
    }
}

Authenticator

public class Authenticator extends AbstractAccountAuthenticator {
    // Simple constructor
    public Authenticator(Context context) {
        super(context);
    }

    // Editing properties is not supported
    @Override
    public Bundle editProperties(
            AccountAuthenticatorResponse r, String s) {
        throw new UnsupportedOperationException();
    }

    // Don't add additional accounts
    @Override
    public Bundle addAccount(
            AccountAuthenticatorResponse r,
            String s,
            String s2,
            String[] strings,
            Bundle bundle) throws NetworkErrorException {
        return null;
    }

    // Ignore attempts to confirm credentials
    @Override
    public Bundle confirmCredentials(
            AccountAuthenticatorResponse r,
            Account account,
            Bundle bundle) throws NetworkErrorException {
        return null;
    }

    // Getting an authentication token is not supported
    @Override
    public Bundle getAuthToken(
            AccountAuthenticatorResponse r,
            Account account,
            String s,
            Bundle bundle) throws NetworkErrorException {
        throw new UnsupportedOperationException();
    }

    // Getting a label for the auth token is not supported
    @Override
    public String getAuthTokenLabel(String s) {
        throw new UnsupportedOperationException();
    }

    // Updating user credentials is not supported
    @Override
    public Bundle updateCredentials(
            AccountAuthenticatorResponse r,
            Account account,
            String s, Bundle bundle) throws NetworkErrorException {
        throw new UnsupportedOperationException();
    }

    // Checking features for the account is not supported
    @Override
    public Bundle hasFeatures(
            AccountAuthenticatorResponse r,
            Account account, String[] strings) throws NetworkErrorException {
        throw new UnsupportedOperationException();
    }
}

Authenticator Service

/**
 * A bound Service that instantiates the authenticator
 * when started.
 */
public class AuthenticatorService extends Service {
    // Instance field that stores the authenticator object
    private Authenticator mAuthenticator;
    @Override
    public void onCreate() {
        // Create a new authenticator object
        mAuthenticator = new Authenticator(this);
    }
    /*
     * When the system binds to this Service to make the RPC call
     * return the authenticator's IBinder.
     */
    @Override
    public IBinder onBind(Intent intent) {
        return mAuthenticator.getIBinder();
    }
}

AndroidManifest.xml additions

<uses-permission android:name="android.permission.GET_ACCOUNTS" />
<uses-permission android:name="android.permission.READ_SYNC_SETTINGS" />
<uses-permission android:name="android.permission.WRITE_SYNC_SETTINGS" />
<uses-permission android:name="android.permission.AUTHENTICATE_ACCOUNTS" />
    
     <service
        android:name=".syncAdapter.SyncService"
        android:exported="true">
        <intent-filter>
            <action android:name="android.content.SyncAdapter" />
        </intent-filter>
        <meta-data
            android:name="android.content.SyncAdapter"
            android:resource="@xml/syncadapter" />
    </service>

    <service android:name=".authenticator.AuthenticatorService">
        <intent-filter>
            <action android:name="android.accounts.AccountAuthenticator" />
        </intent-filter>
        <meta-data
            android:name="android.accounts.AccountAuthenticator"
            android:resource="@xml/authenticator" />
    </service>

    <provider
        android:name=".provider.StubProvider"
        android:authorities="com.yourpackage.provider"
        android:exported="false"
        android:syncable="true" />

res/xml/authenticator.xml

<?xml version="1.0" encoding="utf-8"?>
<account-authenticator xmlns:android="http://schemas.android.com/apk/res/android"
    android:accountType="com.yourpackage"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:smallIcon="@mipmap/ic_launcher" />

res/xml/syncadapter.xml

<?xml version="1.0" encoding="utf-8"?>
<sync-adapter xmlns:android="http://schemas.android.com/apk/res/android"
    android:accountType="com.yourpackage.android"
    android:allowParallelSyncs="false"
    android:contentAuthority="com.yourpackage.provider"
    android:isAlwaysSyncable="true"
    android:supportsUploading="false"
    android:userVisible="false" />

StubProvider

/*
 * Define an implementation of ContentProvider that stubs out
 * all methods
 */
public class StubProvider extends ContentProvider {
    /*
     * Always return true, indicating that the
     * provider loaded correctly.
     */
    @Override
    public boolean onCreate() {
        return true;
    }

    /*
     * Return no type for MIME type
     */
    @Override
    public String getType(Uri uri) {
        return null;
    }

    /*
     * query() always returns no results
     *
     */
    @Override
    public Cursor query(
            Uri uri,
            String[] projection,
            String selection,
            String[] selectionArgs,
            String sortOrder) {
        return null;
    }

    /*
     * insert() always returns null (no URI)
     */
    @Override
    public Uri insert(Uri uri, ContentValues values) {
        return null;
    }

    /*
     * delete() always returns "no rows affected" (0)
     */
    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        return 0;
    }

    /*
     * update() always returns "no rows affected" (0)
     */
    public int update(
            Uri uri,
            ContentValues values,
            String selection,
            String[] selectionArgs) {
        return 0;
    }
}

Call this function on successful login to create an account with the logged-in user ID

 public Account CreateSyncAccount(Context context, String accountName) {
        // Create the account type and default account
        Account newAccount = new Account(
                accountName, "com.yourpackage");
        // Get an instance of the Android account manager
        AccountManager accountManager =
                (AccountManager) context.getSystemService(
                        ACCOUNT_SERVICE);
        /*
         * Add the account and account type, no password or user data
         * If successful, return the Account object, otherwise report an error.
         */
        if (accountManager.addAccountExplicitly(newAccount, null, null)) {
            /*
             * If you don't set android:syncable="true" in
             * in your <provider> element in the manifest,
             * then call context.setIsSyncable(account, AUTHORITY, 1)
             * here.
             */
        } else {
            /*
             * The account exists or some other error occurred. Log this, report it,
             * or handle it internally.
             */
        }
        return newAccount;
    }

Forcing a Sync

Bundle bundle = new Bundle();
bundle.putBoolean(ContentResolver.SYNC_EXTRAS_EXPEDITED, true);
bundle.putBoolean(ContentResolver.SYNC_EXTRAS_FORCE, true);
bundle.putBoolean(ContentResolver.SYNC_EXTRAS_MANUAL, true);
ContentResolver.requestSync(null, MyContentProvider.getAuthority(), bundle);