MOBILE-2966 quiz: Clear answer in multiple choice single answer

scripts/langindex.json

@@ -637,6 +637,7 @@
   "addon.mod_quiz.attemptquiznow": "quiz",
   "addon.mod_quiz.attemptstate": "quiz",
   "addon.mod_quiz.cannotsubmitquizdueto": "local_moodlemobileapp",
+  "addon.mod_quiz.clearchoice": "qtype_multichoice",
   "addon.mod_quiz.comment": "quiz",
   "addon.mod_quiz.completedon": "quiz",
   "addon.mod_quiz.confirmclose": "quiz",

src/addon/mod/quiz/lang/en.json

@@ -6,6 +6,7 @@
     "attemptquiznow": "Attempt quiz now",
     "attemptstate": "State",
     "cannotsubmitquizdueto": "This quiz attempt cannot be submitted for the following reasons:",
+    "clearchoice": "Clear my choice",
     "comment": "Comment",
     "completedon": "Completed on",
     "confirmclose": "Once you submit, you will no longer be able to change your answers for this attempt.",

src/addon/qtype/multichoice/component/addon-qtype-multichoice.html

@@ -32,6 +32,9 @@
             <core-icon item-content *ngIf="option.isCorrect === 1" class="core-correct-icon" name="fa-check" color="success"></core-icon>
             <core-icon item-content *ngIf="option.isCorrect === 0" class="core-correct-icon" name="fa-remove" color="danger"></core-icon>
         </ion-item>
+        <div *ngIf="!question.disabled" padding-horizontal>
+            <button text-wrap [disabled]="!question.singleChoiceModel" ion-button full color="light" (click)="clear()" type="reset">{{ 'addon.mod_quiz.clearchoice' | translate }}</button>
+        </div>
 
         <!-- ion-radio doesn't use an input. Create a hidden input to hold the selected value. -->
         <input type="hidden" [ngModel]="question.singleChoiceModel" [attr.name]="question.optionsName">

src/addon/qtype/multichoice/component/multichoice.ts

@@ -35,4 +35,11 @@ export class AddonQtypeMultichoiceComponent extends CoreQuestionBaseComponent im
     ngOnInit(): void {
         this.initMultichoiceComponent();
     }
+
+    /**
+     * Clear selected choices.
+     */
+    clear(): void {
+        this.question.singleChoiceModel = null;
+    }
 }

src/assets/lang/en.json

@@ -637,6 +637,7 @@
     "addon.mod_quiz.attemptquiznow": "Attempt quiz now",
     "addon.mod_quiz.attemptstate": "State",
     "addon.mod_quiz.cannotsubmitquizdueto": "This quiz attempt cannot be submitted for the following reasons:",
+    "addon.mod_quiz.clearchoice": "Clear my choice",
     "addon.mod_quiz.comment": "Comment",
     "addon.mod_quiz.completedon": "Completed on",
     "addon.mod_quiz.confirmclose": "Once you submit, you will no longer be able to change your answers for this attempt.",

src/core/question/classes/base-question-component.ts

@@ -448,6 +448,8 @@ export class CoreQuestionBaseComponent {
 
             this.question.options = [];
 
+            this.question.disabled = true;
+
             for (const i in options) {
                 const element = options[i],
                     option: any = {
@@ -461,6 +463,8 @@ export class CoreQuestionBaseComponent {
 
                 this.question.optionsName = option.name;
 
+                this.question.disabled = this.question.disabled && element.disabled;
+
                 // Get the label with the question text.
                 const label = questionEl.querySelector('label[for="' + option.id + '"]');
                 if (label) {