[fenix] For https://github.com/mozilla-mobile/fenix/issues/15675: Disable Save button when editing saved login until something has been changed

set save button state by calling invalidateOptionsMenu, causing onPrepareOptionsMenu to be called which will enable/disable the save button depending on if changes have been made or not

app/src/main/java/org/mozilla/fenix/settings/logins/fragment/EditLoginFragment.kt

@@ -13,7 +13,6 @@ import android.view.Menu
 import android.view.MenuInflater
 import android.view.MenuItem
 import android.view.View
-import androidx.appcompat.view.menu.ActionMenuItemView
 import androidx.core.content.ContextCompat
 import androidx.core.view.isVisible
 import androidx.fragment.app.Fragment
@@ -57,7 +56,6 @@ class EditLoginFragment : Fragment(R.layout.fragment_edit_login) {
 
     private var usernameChanged = false
     private var passwordChanged = false
-    private var saveEnabled = false
 
     private var validPassword = true
     private var validUsername = true
@@ -90,8 +88,9 @@ class EditLoginFragment : Fragment(R.layout.fragment_edit_login) {
         usernameText.text = args.savedLoginItem.username.toEditable()
         passwordText.text = args.savedLoginItem.password.toEditable()
 
+        clearUsernameTextButton.isEnabled = oldLogin.username.isNotEmpty()
+
         formatEditableValues()
-        initSaveState()
         setUpClickListeners()
         setUpTextListeners()
         togglePasswordReveal(passwordText, revealPasswordButton)
@@ -101,18 +100,6 @@ class EditLoginFragment : Fragment(R.layout.fragment_edit_login) {
         }
     }
 
-    private fun initSaveState() {
-        saveEnabled = false // don't enable saving until something has been changed
-        val saveButton =
-            activity?.findViewById<ActionMenuItemView>(R.id.save_login_button)
-        saveButton?.isEnabled = saveEnabled
-
-        usernameChanged = false
-        passwordChanged = false
-
-        clearUsernameTextButton.isEnabled = oldLogin.username.isNotEmpty()
-    }
-
     private fun formatEditableValues() {
         hostnameText.isClickable = false
         hostnameText.isFocusable = false
@@ -263,20 +250,20 @@ class EditLoginFragment : Fragment(R.layout.fragment_edit_login) {
     }
 
     private fun setSaveButtonState() {
-        val saveButton = activity?.findViewById<ActionMenuItemView>(R.id.save_login_button)
+        activity?.invalidateOptionsMenu()
-        val changesMadeWithNoErrors =
-            validUsername && validPassword && (usernameChanged || passwordChanged)
-
-        changesMadeWithNoErrors.let {
-            saveButton?.isEnabled = it
-            saveEnabled = it
-        }
     }
 
     override fun onCreateOptionsMenu(menu: Menu, inflater: MenuInflater) {
         inflater.inflate(R.menu.login_save, menu)
     }
 
+    override fun onPrepareOptionsMenu(menu: Menu) {
+        val saveButton = menu.findItem(R.id.save_login_button)
+        val changesMadeWithNoErrors =
+            validUsername && validPassword && (usernameChanged || passwordChanged)
+        saveButton.isEnabled = changesMadeWithNoErrors // don't enable saving until something has been changed
+    }
+
     override fun onPause() {
         redirectToReAuth(
             listOf(R.id.loginDetailFragment),
@@ -288,14 +275,12 @@ class EditLoginFragment : Fragment(R.layout.fragment_edit_login) {
     override fun onOptionsItemSelected(item: MenuItem): Boolean = when (item.itemId) {
         R.id.save_login_button -> {
             view?.hideKeyboard()
-            if (saveEnabled) {
             interactor.onSaveLogin(
                 args.savedLoginItem.guid,
                 usernameText.text.toString(),
                 passwordText.text.toString()
             )
             requireComponents.analytics.metrics.track(Event.EditLoginSave)
-            }
             true
         }
         else -> false