Login into the Dropbox user account

dropboxLogin.kt

fun initDropboxClient() {
  val prefs = getSharedPreferences("recipe-vault", MODE_PRIVATE)

  val serializedCredential = prefs.getString("credential", null)

  if (serializedCredential == null) {
      val credential = Auth.getDbxCredential()

      if (credential != null) {
          prefs.edit().putString("credential", credential.toString()).apply()
          dropboxManager.initDropboxClient(credential)
      }
  }
}

fun DropboxManager.initDropboxClient(credential: DbxCredential) {
  val newCredential = DbxCredential(
      credential.accessToken,
      -1L,
      credential.refreshToken,
      credential.appKey
  )
  if (client == null) {
      client = DbxClientV2(config, newCredential)
  }
}