From 52e1261cc5605eace61a5627f038c57d3fa317c4 Mon Sep 17 00:00:00 2001
From: masclot <eduardj@gmail.com>
Date: Tue, 17 Oct 2023 16:32:42 +0200
Subject: [PATCH] In FractionInteraction UI, leave submit button enabled when
 answer is empty. Show an error on submitting an empty answer.

---
 .../FractionInteractionViewModel.kt           | 30 ++++++++++++-------
 app/src/main/res/values/strings.xml           |  1 +
 2 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/app/src/main/java/org/oppia/android/app/player/state/itemviewmodel/FractionInteractionViewModel.kt b/app/src/main/java/org/oppia/android/app/player/state/itemviewmodel/FractionInteractionViewModel.kt
index 22d42a74744..2360454d433 100644
--- a/app/src/main/java/org/oppia/android/app/player/state/itemviewmodel/FractionInteractionViewModel.kt
+++ b/app/src/main/java/org/oppia/android/app/player/state/itemviewmodel/FractionInteractionViewModel.kt
@@ -43,12 +43,17 @@ class FractionInteractionViewModel private constructor(
         override fun onPropertyChanged(sender: Observable, propertyId: Int) {
           errorOrAvailabilityCheckReceiver.onPendingAnswerErrorOrAvailabilityCheck(
             pendingAnswerError,
-            answerText.isNotEmpty()
+            true // Allow submit on empty answer
           )
         }
       }
     errorMessage.addOnPropertyChangedCallback(callback)
     isAnswerAvailable.addOnPropertyChangedCallback(callback)
+    // Apply defaults:
+    errorOrAvailabilityCheckReceiver.onPendingAnswerErrorOrAvailabilityCheck(
+      null,
+      true
+    )
   }
 
   override fun getPendingAnswer(): UserAnswer = UserAnswer.newBuilder().apply {
@@ -64,23 +69,28 @@ class FractionInteractionViewModel private constructor(
 
   /** It checks the pending error for the current fraction input, and correspondingly updates the error string based on the specified error category. */
   override fun checkPendingAnswerError(category: AnswerErrorCategory): String? {
-    if (answerText.isNotEmpty()) {
-      when (category) {
-        AnswerErrorCategory.REAL_TIME -> {
+    when (category) {
+      AnswerErrorCategory.REAL_TIME -> {
+        if (answerText.isNotEmpty()) {
           pendingAnswerError =
             FractionParsingUiError.createFromParsingError(
               fractionParser.getRealTimeAnswerError(answerText.toString())
             ).getErrorMessageFromStringRes(resourceHandler)
+        } else {
+          pendingAnswerError = null
         }
-        AnswerErrorCategory.SUBMIT_TIME -> {
-          pendingAnswerError =
-            FractionParsingUiError.createFromParsingError(
-              fractionParser.getSubmitTimeError(answerText.toString())
-            ).getErrorMessageFromStringRes(resourceHandler)
+      }
+      AnswerErrorCategory.SUBMIT_TIME -> {
+        pendingAnswerError = if (answerText.isNotEmpty()) {
+          FractionParsingUiError.createFromParsingError(
+            fractionParser.getSubmitTimeError(answerText.toString())
+          ).getErrorMessageFromStringRes(resourceHandler)
+        } else {
+          resourceHandler.getStringInLocale(R.string.interaction_answer_empty_on_submit)
         }
       }
-      errorMessage.set(pendingAnswerError)
     }
+    errorMessage.set(pendingAnswerError)
     return pendingAnswerError
   }
 
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index 79ec1534ff1..30e6545b825 100755
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -606,4 +606,5 @@
   <string name="lock_icon_content_description">Lock Icon</string>
   <string name="download_status_image_content_description">Download Status</string>
   <string name="font_scale_html_content_text">html Content</string>
+  <string name="interaction_answer_empty_on_submit">"Enter an answer to continue"</string>
 </resources>