fix: Handle units with no descendants (#29) (#405)

Author: dixidroid

course/src/main/java/org/openedx/course/presentation/ui/CourseUI.kt

@@ -884,15 +884,15 @@ fun SubSectionUnitsTitle(
     onUnitsClick: () -> Unit,
 ) {
     val textStyle = MaterialTheme.appTypography.titleMedium
-    val hasUnits = unitsCount > 0
+    val hasMultipleUnits = unitsCount > 1
     var rowModifier = Modifier
         .fillMaxWidth()
         .padding(
             horizontal = 16.dp,
             vertical = 8.dp
         )
         .displayCutoutForLandscape()
-    if (hasUnits) {
+    if (hasMultipleUnits) {
         rowModifier = rowModifier.noRippleClickable { onUnitsClick() }
     }
 
@@ -912,7 +912,7 @@ fun SubSectionUnitsTitle(
             textAlign = TextAlign.Start
         )
 
-        if (hasUnits) {
+        if (hasMultipleUnits) {
             Icon(
                 modifier = Modifier.rotate(if (unitsListShowed) 180f else 0f),
                 painter = painterResource(id = R.drawable.ic_course_arrow_down),

course/src/main/java/org/openedx/course/presentation/unit/container/CourseUnitContainerFragment.kt

@@ -281,21 +281,24 @@ class CourseUnitContainerFragment : Fragment(R.layout.fragment_course_unit_conta
 
             binding.subSectionUnitsList.setContent {
                 val unitBlocks by viewModel.subSectionUnitBlocks.collectAsState()
-                val selectedUnitIndex = unitBlocks.indexOfFirst { it.id == viewModel.unitId }
-                OpenEdXTheme {
-                    SubSectionUnitsList(
-                        unitBlocks = unitBlocks,
-                        selectedUnitIndex = selectedUnitIndex
-                    ) { index, unit ->
-                        if (index != selectedUnitIndex) {
-                            router.navigateToCourseContainer(
-                                fm = requireActivity().supportFragmentManager,
-                                courseId = viewModel.courseId,
-                                unitId = unit.id,
-                                mode = requireArguments().serializable(ARG_MODE)!!
-                            )
-                        } else {
-                            handleUnitsClick()
+                // If there is more than one unit in the section, show the list
+                if (unitBlocks.size > 1) {
+                    val selectedUnitIndex = unitBlocks.indexOfFirst { it.id == viewModel.unitId }
+                    OpenEdXTheme {
+                        SubSectionUnitsList(
+                            unitBlocks = unitBlocks,
+                            selectedUnitIndex = selectedUnitIndex
+                        ) { index, unit ->
+                            if (index != selectedUnitIndex) {
+                                router.navigateToCourseContainer(
+                                    fm = requireActivity().supportFragmentManager,
+                                    courseId = viewModel.courseId,
+                                    unitId = unit.id,
+                                    mode = requireArguments().serializable(ARG_MODE)!!
+                                )
+                            } else {
+                                handleUnitsClick()
+                            }
                         }
                     }
                 }

course/src/main/java/org/openedx/course/presentation/unit/container/CourseUnitContainerViewModel.kt

@@ -138,6 +138,10 @@ class CourseUnitContainerViewModel(
                         }
                     _subSectionUnitBlocks.value =
                         getSubSectionUnitBlocks(blocks, getSubSectionId(unitId))
+
+                    if (_descendantsBlocks.value.isEmpty()) {
+                        _descendantsBlocks.value = listOf(block)
+                    }
                 } else {
                     setNextVerticalIndex()
                 }