Before you can use Realm in your app, you must initialize the Realm library. Your application should initialize Realm just once each time the application runs.
To initialize the Realm library, provide an Android
context to the
Realm.init() static function. You can provide
an Activity, Fragment, or Application
context for initialization with no
difference in behavior. You can initialize the Realm library
onCreate() method of an application subclass to
ensure that you only initialize Realm once each time the
Register Your Application Subclass in the Android Manifest
If you create your own
Application subclass, you must add it to your
AndroidManifest.xml to execute your custom
application logic. Set the
android.name property of your manifest's
application definition to ensure that Android instantiates your
subclass before any other class when a user launches your application.
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.mongodb.example"> <application android:name=".MyApplicationSubclass" ... /> </manifest>
Pass the App ID for your App, which you can find in the Realm UI.
Initialize the App before Creating an Instance
You must initialize your App connection with
Realm.init() before creating any instance of an
For most use cases, you only need your application's App ID to connect
to App Services. For more granular control of the details of your app connection,
such as custom timeouts for connections, codecs used for MongoDB Data Access,
and keys for local encryption, you can optionally use the
Builder to control details of your
You can create multiple App client instances to connect to multiple Apps. All App client instances that share the same App ID use the same underlying connection.
You Can't Change an App Config After Initializing the App
When you initialize the App client, the configuration is cached internally. Attempting to "close" an App and then re-open it with a changed configuration within the same process has no effect. The client continues to use the cached configuration.