Fix: Prevent crash when pausing/resuming uploads after screen rotation

app/src/main/java/fr/free/nrw/commons/upload/PendingUploadsFragment.kt

@@ -28,6 +28,7 @@ class PendingUploadsFragment :
     CommonsDaggerSupportFragment(),
     PendingUploadsContract.View,
     PendingUploadsAdapter.Callback {
+    // final-state:Non-nullable lateinit var as the Presenter is always initialized.
     @Inject
     lateinit var pendingUploadsPresenter: PendingUploadsPresenter
 
@@ -60,10 +61,6 @@ class PendingUploadsFragment :
         return binding.root
     }
 
-    fun initAdapter() {
-        adapter = PendingUploadsAdapter(this)
-    }
-
     override fun onViewCreated(
         view: View,
         savedInstanceState: Bundle?,
@@ -72,6 +69,10 @@ class PendingUploadsFragment :
         initRecyclerView()
     }
 
+    fun initAdapter() {
+        adapter = PendingUploadsAdapter(this)
+    }
+
     /**
      * Initializes the recycler view.
      */
@@ -81,38 +82,38 @@ class PendingUploadsFragment :
         pendingUploadsPresenter.setup()
         pendingUploadsPresenter.totalContributionList
             .observe(viewLifecycleOwner) { list: PagedList<Contribution> ->
-            contributionsSize = list.size
-            contributionsList = mutableListOf()
-            var pausedOrQueuedUploads = 0
-            list.forEach {
-                if (it != null) {
-                    if (it.state == STATE_PAUSED ||
-                        it.state == STATE_QUEUED ||
-                        it.state == STATE_IN_PROGRESS
-                    ) {
-                        contributionsList.add(it)
-                    }
-                    if (it.state == STATE_PAUSED || it.state == STATE_QUEUED) {
-                        pausedOrQueuedUploads++
+                contributionsSize = list.size
+                contributionsList = mutableListOf()
+                var pausedOrQueuedUploads = 0
+                list.forEach {
+                    if (it != null) {
+                        if (it.state == STATE_PAUSED ||
+                            it.state == STATE_QUEUED ||
+                            it.state == STATE_IN_PROGRESS
+                        ) {
+                            contributionsList.add(it)
+                        }
+                        if (it.state == STATE_PAUSED || it.state == STATE_QUEUED) {
+                            pausedOrQueuedUploads++
+                        }
                     }
                 }
-            }
-            if (contributionsSize == 0) {
-                binding.nopendingTextView.visibility = View.VISIBLE
-                binding.pendingUplaodsLl.visibility = View.GONE
-                uploadProgressActivity.hidePendingIcons()
-            } else {
-                binding.nopendingTextView.visibility = View.GONE
-                binding.pendingUplaodsLl.visibility = View.VISIBLE
-                adapter.submitList(list)
-                binding.progressTextView.setText("$contributionsSize uploads left")
-                if ((pausedOrQueuedUploads == contributionsSize) || CommonsApplication.isPaused) {
-                    uploadProgressActivity.setPausedIcon(true)
+                if (contributionsSize == 0) {
+                    binding.nopendingTextView.visibility = View.VISIBLE
+                    binding.pendingUplaodsLl.visibility = View.GONE
+                    uploadProgressActivity.hidePendingIcons()
                 } else {
-                    uploadProgressActivity.setPausedIcon(false)
+                    binding.nopendingTextView.visibility = View.GONE
+                    binding.pendingUplaodsLl.visibility = View.VISIBLE
+                    adapter.submitList(list)
+                    binding.progressTextView.setText("$contributionsSize uploads left")
+                    if ((pausedOrQueuedUploads == contributionsSize) || CommonsApplication.isPaused) {
+                        uploadProgressActivity.setPausedIcon(true)
+                    } else {
+                        uploadProgressActivity.setPausedIcon(false)
+                    }
                 }
             }
-        }
     }
 
     /**
@@ -140,19 +141,24 @@ class PendingUploadsFragment :
     /**
      * Restarts all the paused uploads.
      */
-    fun restartUploads() = pendingUploadsPresenter.restartUploads(
-        contributionsList, 0, requireContext().applicationContext
-    )
+    fun restartUploads() {
+        pendingUploadsPresenter.restartUploads(
+            contributionsList, 0, requireContext().applicationContext
+        )
+    }
 
     /**
      * Pauses all the ongoing uploads.
      */
-    fun pauseUploads() = pendingUploadsPresenter.pauseUploads()
+    fun pauseUploads() {
+        pendingUploadsPresenter.pauseUploads()
+    }
 
     /**
      * Cancels all the uploads after getting a confirmation from the user using Dialog.
      */
     fun deleteUploads() {
+        //final change:thee redundant 'if (!::pendingUploadsPresenter.isInitialized) return' is removed.
         val activity = requireActivity()
         val locale = Locale.getDefault()
         showAlertDialog(
@@ -175,4 +181,4 @@ class PendingUploadsFragment :
             {},
         )
     }
-}
+}

app/src/main/java/fr/free/nrw/commons/upload/UploadProgressActivity.kt

@@ -21,8 +21,6 @@ import javax.inject.Inject
  */
 class UploadProgressActivity : BaseActivity() {
     private lateinit var binding: ActivityUploadProgressBinding
-    private var pendingUploadsFragment: PendingUploadsFragment? = null
-    private var failedUploadsFragment: FailedUploadsFragment? = null
     var viewPagerAdapter: ViewPagerAdapter? = null
     var menu: Menu? = null
 
@@ -68,18 +66,38 @@ class UploadProgressActivity : BaseActivity() {
         setTabs()
     }
 
+    //helper to retrieve the current Fragment by CLASS TYPE (as suggested).
+    private fun getPendingUploadsFragment(): PendingUploadsFragment? {
+        //find the Fragment by class type, not index
+        return supportFragmentManager.fragments.find {
+            it is PendingUploadsFragment && it.isAdded
+        } as? PendingUploadsFragment
+    }
+
+    private fun getFailedUploadsFragment(): FailedUploadsFragment? {
+        //find the Fragment by class type, not index
+        return supportFragmentManager.fragments.find {
+            it is FailedUploadsFragment && it.isAdded
+        } as? FailedUploadsFragment
+    }
+
+
     /**
      * Initializes and sets up the tabs data by creating instances of `PendingUploadsFragment`
      * and `FailedUploadsFragment`, adds them to the `fragmentList`, and assigns corresponding
      * titles from resources to the `titleList`.
      */
     fun setTabs() {
-        pendingUploadsFragment = PendingUploadsFragment()
-        failedUploadsFragment = FailedUploadsFragment()
+        val pendingUploadsFragment: Fragment
+        val failedUploadsFragment: Fragment
+
+        // using the robust getPendingUploadsFragment() helper
+        pendingUploadsFragment = getPendingUploadsFragment() ?: PendingUploadsFragment()
+        failedUploadsFragment = getFailedUploadsFragment() ?: FailedUploadsFragment()
 
         viewPagerAdapter!!.setTabs(
-            R.string.pending to pendingUploadsFragment!!,
-            R.string.failed to failedUploadsFragment!!
+            R.string.pending to pendingUploadsFragment,
+            R.string.failed to failedUploadsFragment
         )
         viewPagerAdapter!!.notifyDataSetChanged()
     }
@@ -119,7 +137,8 @@ class UploadProgressActivity : BaseActivity() {
                                     getString(R.string.pause),
                                 ).setIcon(R.drawable.pause_icon)
                                 .setOnMenuItemClickListener {
-                                    pendingUploadsFragment!!.pauseUploads()
+                                    //robust helper to find the correct instance
+                                    getPendingUploadsFragment()?.pauseUploads()
                                     setPausedIcon(true)
                                     true
                                 }.setShowAsAction(MenuItem.SHOW_AS_ACTION_IF_ROOM)
@@ -133,7 +152,8 @@ class UploadProgressActivity : BaseActivity() {
                                     getString(R.string.cancel),
                                 ).setIcon(R.drawable.ic_cancel_upload)
                                 .setOnMenuItemClickListener {
-                                    pendingUploadsFragment!!.deleteUploads()
+                                    //robust helper to find the correct instance
+                                    getPendingUploadsFragment()?.deleteUploads()
                                     true
                                 }.setShowAsAction(MenuItem.SHOW_AS_ACTION_IF_ROOM)
                         }
@@ -147,7 +167,8 @@ class UploadProgressActivity : BaseActivity() {
                                     getString(R.string.resume),
                                 ).setIcon(R.drawable.play_icon)
                                 .setOnMenuItemClickListener {
-                                    pendingUploadsFragment!!.restartUploads()
+                                    //robust helper to find the correct instance
+                                    getPendingUploadsFragment()?.restartUploads()
                                     setPausedIcon(false)
                                     true
                                 }.setShowAsAction(MenuItem.SHOW_AS_ACTION_IF_ROOM)
@@ -161,7 +182,7 @@ class UploadProgressActivity : BaseActivity() {
                             .add(Menu.NONE, R.id.retry_icon, Menu.NONE, getString(R.string.retry))
                             .setIcon(R.drawable.ic_refresh_24dp)
                             .setOnMenuItemClickListener {
-                                failedUploadsFragment!!.restartUploads()
+                                getFailedUploadsFragment()?.restartUploads()
                                 true
                             }.setShowAsAction(MenuItem.SHOW_AS_ACTION_IF_ROOM)
                     }
@@ -174,7 +195,7 @@ class UploadProgressActivity : BaseActivity() {
                                 getString(R.string.cancel),
                             ).setIcon(R.drawable.ic_cancel_upload)
                             .setOnMenuItemClickListener {
-                                failedUploadsFragment!!.deleteUploads()
+                                getFailedUploadsFragment()?.deleteUploads()
                                 true
                             }.setShowAsAction(MenuItem.SHOW_AS_ACTION_IF_ROOM)
                     }