Add restore credential snippets (#489)

Co-authored-by: Neelansh Sahai <[email protected]>

Author: neelanshsahai

identity/credentialmanager/src/main/java/com/example/identity/credentialmanager/RestoreCredentialsFunctions.kt

@@ -0,0 +1,70 @@
+/*
+ * Copyright 2025 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.example.identity.credentialmanager
+
+import android.content.Context
+import androidx.credentials.ClearCredentialStateRequest
+import androidx.credentials.ClearCredentialStateRequest.Companion.TYPE_CLEAR_RESTORE_CREDENTIAL
+import androidx.credentials.CreateRestoreCredentialRequest
+import androidx.credentials.CredentialManager
+import androidx.credentials.GetCredentialRequest
+import androidx.credentials.GetRestoreCredentialOption
+
+class RestoreCredentialsFunctions(
+    private val context: Context,
+    private val credentialManager: CredentialManager,
+) {
+    suspend fun createRestoreKey(
+        createRestoreRequest: CreateRestoreCredentialRequest
+    ) {
+        // [START android_identity_restore_cred_create]
+        val credentialManager = CredentialManager.create(context)
+
+        // On a successful authentication create a Restore Key
+        // Pass in the context and CreateRestoreCredentialRequest object
+        val response = credentialManager.createCredential(context, createRestoreRequest)
+        // [END android_identity_restore_cred_create]
+    }
+
+    suspend fun getRestoreKey(
+        fetchAuthenticationJson: () -> String,
+    ) {
+        // [START android_identity_restore_cred_get]
+        // Fetch the Authentication JSON from server
+        val authenticationJson = fetchAuthenticationJson()
+
+        // Create the GetRestoreCredentialRequest object
+        val options = GetRestoreCredentialOption(authenticationJson)
+        val getRequest = GetCredentialRequest(listOf(options))
+
+        // The restore key can be fetched in two scenarios to
+        // 1. On the first launch of app on the device, fetch the Restore Key
+        // 2. In the onRestore callback (if the app implements the Backup Agent)
+        val response = credentialManager.getCredential(context, getRequest)
+        // [END android_identity_restore_cred_get]
+    }
+
+    suspend fun deleteRestoreKey() {
+        // [START android_identity_restore_cred_delete]
+        // Create a ClearCredentialStateRequest object
+        val clearRequest = ClearCredentialStateRequest(TYPE_CLEAR_RESTORE_CREDENTIAL)
+
+        // On user log-out, clear the restore key
+        val response = credentialManager.clearCredentialState(clearRequest)
+        // [END android_identity_restore_cred_delete]
+    }
+}