Remember the comments progress, scroll to top button for comments

app/src/main/java/com/github/libretube/ui/adapters/CommentsAdapter.kt

@@ -1,8 +1,6 @@
 package com.github.libretube.ui.adapters
 
 import android.annotation.SuppressLint
-import android.os.Handler
-import android.os.Looper
 import android.text.method.LinkMovementMethod
 import android.view.*
 import android.view.ViewGroup.MarginLayoutParams

app/src/main/java/com/github/libretube/ui/fragments/CommentsMainFragment.kt

@@ -4,6 +4,7 @@ import android.os.Bundle
 import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
+import androidx.core.view.isVisible
 import androidx.fragment.app.Fragment
 import androidx.fragment.app.activityViewModels
 import androidx.recyclerview.widget.LinearLayoutManager
@@ -11,6 +12,7 @@ import com.github.libretube.R
 import com.github.libretube.databinding.FragmentCommentsBinding
 import com.github.libretube.ui.adapters.CommentsAdapter
 import com.github.libretube.ui.models.CommentsViewModel
+import com.github.libretube.ui.sheets.CommentsSheet
 
 class CommentsMainFragment : Fragment() {
     private var _binding: FragmentCommentsBinding? = null
@@ -32,11 +34,25 @@ class CommentsMainFragment : Fragment() {
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
         super.onViewCreated(view, savedInstanceState)
 
-        binding.commentsRV.layoutManager = LinearLayoutManager(requireContext())
+        val layoutManager = LinearLayoutManager(requireContext())
+        binding.commentsRV.layoutManager = layoutManager
         binding.commentsRV.setItemViewCacheSize(20)
 
         binding.commentsRV.viewTreeObserver.addOnScrollChangedListener {
-            if (_binding?.commentsRV?.canScrollVertically(1) == false) {
+            val binding = _binding ?: return@addOnScrollChangedListener
+            // save the last scroll position to become used next time when the sheet is opened
+            viewModel.currentCommentsPosition = layoutManager.findFirstVisibleItemPosition()
+
+            // hide or show the scroll to top button
+            val commentsSheetBinding = (parentFragment as? CommentsSheet)?.binding
+            commentsSheetBinding?.btnScrollToTop?.isVisible = viewModel.currentCommentsPosition != 0
+            commentsSheetBinding?.btnScrollToTop?.setOnClickListener {
+                // scroll back to the top / first comment
+                binding.commentsRV.smoothScrollToPosition(0)
+                viewModel.currentCommentsPosition = 0
+            }
+
+            if (!binding.commentsRV.canScrollVertically(1)) {
                 viewModel.fetchNextComments()
             }
         }
@@ -54,6 +70,8 @@ class CommentsMainFragment : Fragment() {
         if (viewModel.commentsPage.value?.comments.orEmpty().isEmpty()) {
             binding.progress.visibility = View.VISIBLE
             viewModel.fetchComments()
+        } else {
+            binding.commentsRV.scrollToPosition(viewModel.currentCommentsPosition)
         }
 
         // listen for new comments to be loaded

app/src/main/java/com/github/libretube/ui/models/CommentsViewModel.kt

@@ -18,6 +18,8 @@ class CommentsViewModel : ViewModel() {
 
     val commentSheetExpand = MutableLiveData<Boolean?>()
 
+    var currentCommentsPosition = 0
+
     fun setCommentSheetExpand(value: Boolean?) {
         if (commentSheetExpand.value != value) {
             commentSheetExpand.value = value
@@ -73,5 +75,6 @@ class CommentsViewModel : ViewModel() {
         commentsPage.value = null
         videoId = null
         setCommentSheetExpand(null)
+        currentCommentsPosition = 0
     }
 }

app/src/main/java/com/github/libretube/ui/sheets/CommentsSheet.kt

@@ -17,7 +17,7 @@ import com.github.libretube.ui.fragments.CommentsRepliesFragment
 import com.github.libretube.ui.models.CommentsViewModel
 
 class CommentsSheet : ExpandedBottomSheet() {
-    private lateinit var binding: CommentsSheetBinding
+    lateinit var binding: CommentsSheetBinding
     private val commentsViewModel: CommentsViewModel by activityViewModels()
 
     override fun onCreateView(

app/src/main/res/layout/comments_sheet.xml

@@ -52,6 +52,16 @@
                     android:textAlignment="viewStart"
                     tools:text="Title" />
 
+                <androidx.appcompat.widget.AppCompatImageView
+                    android:visibility="gone"
+                    android:id="@+id/btnScrollToTop"
+                    android:layout_width="35dp"
+                    android:layout_height="35dp"
+                    android:src="@drawable/ic_arrow_downward"
+                    android:rotationX="180"
+                    android:padding="7dp"
+                    android:background="?selectableItemBackgroundBorderless" />
+
                 <androidx.appcompat.widget.AppCompatImageView
                     android:id="@+id/btnClose"
                     android:layout_width="35dp"