I think I have this figured out:
"Use this redirect URL when creating the OAuthConfiguration and the intent filter scheme when Android returns control back to your app after OAuth 2.0 login. If you change this value, you must change it in all three places.
If you already have an app defined, you can use that client ID instead of creating a new one." (you have to click the circle-i to open this)
On developers.argis.com, in the Authetican tab of you application, add the redirect uri "<app_name>://auth"
In the strings.xml create
<string name="oauth_client_id"><Copied client ID></string>
<string name="oauth_redirect_host">auth</string>
<string name="oauth_redirect_uri">APP_NAME</string>
In the java code:OAuthConfiguration oAuthConfiguration = new OAuthConfiguration(portalURL, getString(R.string.oauth_client_id), getString(R.string.oauth_redirect_uri) + "://" + getString(R.string.oauth_redirect_host));
In the manifest.xml:
<!-- You must declare this activity, an intent receiver, to display the OAuth login -->
<activity
android:name="com.esri.arcgisruntime.security.DefaultOAuthIntentReceiver"
android:launchMode="singleTask">
<intent-filter>
<action android:name="android.intent.action.VIEW" />
<category android:name="android.intent.category.DEFAULT" />
<category android:name="android.intent.category.BROWSABLE" />
<data
android:host="@string/oauth_redirect_host"
android:scheme=APP_NAME /> <!-- CHANGE APP NAME HERE!!!! -->
</intent-filter>
</activity>