Login: Show error message when account name is already taken

app/src/main/java/at/bitfire/davdroid/ui/setup/AccountDetailsFragment.kt

@@ -81,6 +81,13 @@ class AccountDetailsFragment: Fragment() {
             if (name.isEmpty())
                 v.account_name.error = getString(R.string.login_account_name_required)
             else {
+                // check whether account name already exists
+                val am = AccountManager.get(requireActivity())
+                if (am.getAccountsByType(getString(R.string.account_type)).any { it.name == name }) {
+                    v.account_name.error = getString(R.string.login_account_name_already_taken)
+                    return@setOnClickListener
+                }
+
                 val idx = view!!.contact_group_method.selectedItemPosition
                 val groupMethodName = resources.getStringArray(R.array.settings_contact_group_method_values)[idx]
 

app/src/main/res/values/strings.xml

@@ -159,6 +159,7 @@
     <string name="login_account_name_info">Use your email address as account name because Android will use the account name as ORGANIZER field for events you create. You can\'t have two accounts with the same name.</string>
     <string name="login_account_contact_group_method">Contact group method:</string>
     <string name="login_account_name_required">Account name required</string>
+    <string name="login_account_name_already_taken">Account name already taken</string>
     <string name="login_account_not_created">Account could not be created</string>
 
     <string name="login_configuration_detection">Configuration detection</string>