Android Sync Adaper - https://www.pilanites.com/android-sync-adapter/

AndroidManifest.xml

<uses-permission android:name="android.permission.READ_SYNC_SETTINGS" />
<uses-permission android:name="android.permission.WRITE_SYNC_SETTINGS" />
<uses-permission android:name="android.permission.READ_SYNC_STATS" />

<application>
    <service
        android:name="com.pilanites.streaks.SyncService"
        android:exported="true"
        android:process=":sync">
        <intent-filter>
            <action android:name="android.content.SyncAdapter" />
        </intent-filter>

        <meta-data
            android:name="android.content.SyncAdapter"
            android:resource="@xml/syncadapter" />
    </service>

    <provider
        android:name="com.activeandroid.content.ContentProvider"
        android:authorities="@string/content_authority"
        android:exported="false" />
</application>

ExecuteSync.java

public void sync() {
    Account account = UserAccountUtil.getAccount(this);
    Bundle settingsBundle = new Bundle();
    settingsBundle.putBoolean(ContentResolver.SYNC_EXTRAS_MANUAL, true);
    settingsBundle.putBoolean(ContentResolver.SYNC_EXTRAS_EXPEDITED, true);
    /*
     * Request the sync for the default account, authority, and
     * manual sync settings
     */
    ContentResolver.requestSync(account, getResources().getString(R.string.content_authority), settingsBundle);
}

SyncAdapter.java

public class SyncAdapter extends AbstractThreadedSyncAdapter {
 
    private AccountManager mAccountManager;
 
    public SyncAdapter(Context context, boolean autoInitialize) {
        super(context, autoInitialize);
        mAccountManager = AccountManager.get(context);
    }
 
    public SyncAdapter(Context context, boolean autoInitialize, boolean allowParallelSyncs) {
        super(context, autoInitialize, allowParallelSyncs);
        mAccountManager = AccountManager.get(context);
    }
 
    @Override
    public void onPerformSync(Account account, Bundle extras,
                              String authority, ContentProviderClient provider,
                              SyncResult syncResult) {
        try {
            String authToken = mAccountManager.blockingGetAuthToken(account,
                    AccountConstants.AUTH_TOKEN_TYPE, true);
            // Use the authToken and write your sync logic. Skip the previous call if authToken is not required
        } catch (OperationCanceledException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (AuthenticatorException e) {
            e.printStackTrace();
        }
    }
}

syncadapter.xml

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

SyncService.java

/**
 * 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();
    }
}

UserAccountUtil.java

// Use this method to get an instance of Account.
public static Account getAccount(Context context) {
  if (ActivityCompat.checkSelfPermission(context,
        android.Manifest.permission.GET_ACCOUNTS) != PackageManager.PERMISSION_GRANTED) {
    Log.d(TAG, "GET_ACCOUNTS not present.");
  }

  AccountManager accountManager = AccountManager.get(context);
  Account[] accounts = accountManager.getAccountsByType(AccountConstants.ACCOUNT_TYPE);
  if (accounts.length > 0) {
    return accounts[0];
  } else {
    return null;
  }
}