Hi,

This is ContactSyncBackground Demo as you see whatsapp,viber or other apps

To run this project you need to add appcompat library

I followed this process to achieve syncing in backgroun

1. Create AuthenticatorService and ContactsSyncAdapter Service class. AuthenticatorService Class is for when you create syncing account then this service run so you can perform any operation during creating account or add account in setting.

2. To create account SyncUtils.CreateAccount(instance, user, pass);

3. When account created successfully then you want to sync your contacts, ContactsSyncAdapterService is run when you perform syncing either manually(using setting) or automatically.

4. To perform syncing automatically

    AccountManager am = AccountManager.get(instance);
    Account[] acclist = am.getAccounts();
    for (Account acc : acclist) {
    	if (acc.type.equals(SyncUtils.ACCOUNT_TYPE)) {
    		// You need pass bundle to sync
    		Bundle b = new Bundle();
    		b.putBoolean(ContentResolver.SYNC_EXTRAS_MANUAL, true);
    		b.putBoolean(ContentResolver.SYNC_EXTRAS_EXPEDITED, true);
    		ContentResolver.requestSync(acc, SyncUtils.AUTHORITY, b);
   
    		Log.i("MainActivity", "Request to sync Contacts");
    	}
    }
   

5. After firing this operation onPerformSync() method called in ContactsSyncAdapterService Here you can perform network syncing operation. I poupulated the contacts in json and post to server and server returning me intersection of contacts.

6. You need to register this service in Manifiest

    <service
        android:name="com.iqbal.contactsyncbg.sync.ContactsSyncAdapterService"
        android:exported="true"
        android:process=":contacts" >
        <intent-filter>
            <action android:name="android.content.SyncAdapter" />
        </intent-filter>
   
        <meta-data
            android:name="android.content.SyncAdapter"
            android:resource="@xml/sync_contacts" />
        <meta-data
            android:name="android.provider.CONTACTS_STRUCTURE"
            android:resource="@xml/contacts" />
    </service>
    <service
        android:name="com.iqbal.contactsyncbg.sync.AuthenticatorService"
        android:exported="true"
        android:process=":auth" >
        <intent-filter>
            <action android:name="android.accounts.AccountAuthenticator" />
        </intent-filter>
   
        <meta-data
            android:name="android.accounts.AccountAuthenticator"
            android:resource="@xml/authenticator" />
    </service>
   

7.At last you need to add permission

<uses-permission android:name="android.permission.READ_CONTACTS" />
<uses-permission android:name="android.permission.WRITE_CONTACTS" />
<uses-permission android:name="android.permission.GET_ACCOUNTS" />
<uses-permission android:name="android.permission.MANAGE_ACCOUNTS" />
<uses-permission android:name="android.permission.AUTHENTICATE_ACCOUNTS" />
<uses-permission android:name="android.permission.READ_SYNC_SETTINGS" />
<uses-permission android:name="android.permission.WRITE_SYNC_SETTINGS" />

8.Be sure of Account Type what you defined in sync_contacts and ContactSyncAdapter must be same. Otherwise you will get this exception caller uid is different than the authenticator's uid to fix this exception you need to check account type.