Hide "Collect data" button when the job has no more tasks to complete

ground/src/main/java/com/google/android/ground/model/job/Job.kt

@@ -54,6 +54,9 @@ data class Job(
 
   /** Returns true if the job has one or more tasks. */
   fun hasTasks() = tasks.values.isNotEmpty()
+
+  /** Returns whether the job has non-LOI tasks. */
+  fun hasNonLoiTasks() = tasks.values.count { !it.isAddLoiTask } > 0
 }
 
 fun Job.getDefaultColor(): Int =

ground/src/main/java/com/google/android/ground/ui/datacollection/DataCollectionViewModel.kt

@@ -321,17 +321,18 @@ internal constructor(
     if (tasks.isEmpty()) {
       error("Can't generate sequence for empty task list")
     }
-
-    val task = tasks.filter { it.id == (startId ?: tasks[0].id) }
-
-    // TODO(#2539): Cleanup once https://github.com/google/ground-android/issues/2539 is resolved.
-    if (task.isEmpty()) {
-      error(
-        "Unable to find a task with id startId=$startId, firstTaskId=${tasks[0].id}, allTasks=${tasks.map { it.id }}"
-      )
-    }
-
-    val startIndex = tasks.indexOf(task.first())
+    val startIndex =
+      tasks
+        .indexOfFirst { it.id == (startId ?: tasks[0].id) }
+        .let {
+          // NOTE(#2539) Fallback to the first task if startId is not found.
+          if (it < 0) {
+            Timber.w("startId, $startId, was not found. Defaulting to 0")
+            0
+          } else {
+            it
+          }
+        }
     return if (reversed) {
         tasks.subList(0, startIndex + 1).reversed()
       } else {

ground/src/main/java/com/google/android/ground/ui/home/mapcontainer/HomeScreenMapContainerFragment.kt

@@ -79,7 +79,7 @@ class HomeScreenMapContainerFragment : AbstractMapContainerFragment() {
       val canUserSubmitData = userRepository.canUserSubmitData()
 
       // Handle collect button clicks
-      adapter.setCollectDataListener { onCollectData(canUserSubmitData, it) }
+      adapter.setCollectDataListener { onCollectData(canUserSubmitData, hasValidTasks(it), it) }
 
       // Bind data for cards
       mapContainerViewModel.getMapCardUiData().launchWhenStartedAndCollect { (mapCards, loiCount) ->
@@ -90,15 +90,32 @@ class HomeScreenMapContainerFragment : AbstractMapContainerFragment() {
     map.featureClicks.launchWhenStartedAndCollect { mapContainerViewModel.onFeatureClicked(it) }
   }
 
+  private fun hasValidTasks(cardUiData: MapCardUiData) =
+    when (cardUiData) {
+      // LOI tasks are filtered out of the tasks list for pre-defined tasks.
+      is MapCardUiData.LoiCardUiData ->
+        cardUiData.loi.job.tasks.values.count { !it.isAddLoiTask } > 0
+      is MapCardUiData.AddLoiCardUiData -> cardUiData.job.tasks.values.isNotEmpty()
+    }
+
   /** Invoked when user clicks on the map cards to collect data. */
-  private fun onCollectData(canUserSubmitData: Boolean, cardUiData: MapCardUiData) {
-    if (canUserSubmitData) {
-      navigateToDataCollectionFragment(cardUiData)
-    } else {
+  private fun onCollectData(
+    canUserSubmitData: Boolean,
+    hasTasks: Boolean,
+    cardUiData: MapCardUiData,
+  ) {
+    if (!canUserSubmitData) {
       // Skip data collection screen if the user can't submit any data
       // TODO(#1667): Revisit UX for displaying view only mode
       ephemeralPopups.ErrorPopup().show(getString(R.string.collect_data_viewer_error))
+      return
+    }
+    if (!hasTasks) {
+      // NOTE(#2539): The DataCollectionFragment will crash if there are no tasks.
+      ephemeralPopups.ErrorPopup().show(getString(R.string.no_tasks_error))
+      return
     }
+    navigateToDataCollectionFragment(cardUiData)
   }
 
   /** Updates the given [TextView] with the submission count for the given [LocationOfInterest]. */

ground/src/main/java/com/google/android/ground/ui/home/mapcontainer/cards/MapCardAdapter.kt

@@ -145,8 +145,9 @@ class MapCardAdapter(
       with(binding) {
         loiName.text = loiHelper.getDisplayLoiName(loi)
         jobName.text = loiHelper.getJobName(loi)
+        // NOTE(#2539): The DataCollectionFragment will crash if there are no non-LOI tasks.
         collectData.visibility =
-          if (canUserSubmitData && loi.job.hasTasks()) View.VISIBLE else View.GONE
+          if (canUserSubmitData && loi.job.hasNonLoiTasks()) View.VISIBLE else View.GONE
         updateSubmissionCount(loi, submissions)
       }
     }

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

@@ -90,6 +90,7 @@
   <string name="drop_a_pin_tooltip_text">Drag your map until the center pin is on the desired location</string>
   <string name="current_location">Current location:</string>
   <string name="loading">Loading…</string>
+  <string name="no_tasks_error">This job has no more tasks to complete</string>
   <string name="collect_data_viewer_error">Can’t collect data as user is a VIEWER</string>
   <string name="offline_map_imagery">Offline map imagery</string>
   <string name="offline_map_imagery_pref_description">Hide or show downloaded imagery</string>