Merge pull request #817 from vector-im/feature/fab_scroll

Show skip to bottom FAB while scrolling down (#752)

CHANGES.md

@@ -12,6 +12,7 @@ Improvements 🙌:
  - Improve devices list screen
  - Add settings for rageshake sensibility
  - Fix autocompletion issues and add support for rooms, groups, and emoji (#780)
+ - Show skip to bottom FAB while scrolling down (#752)
 
 Other changes:
  - Change the way RiotX identifies a session to allow the SDK to support several sessions with the same user (#800)

vector/src/main/java/im/vector/riotx/core/utils/Debouncer.kt

@@ -19,16 +19,14 @@ package im.vector.riotx.core.utils
 
 import android.os.Handler
 
-internal class Debouncer(private val handler: Handler) {
+class Debouncer(private val handler: Handler) {
 
     private val runnables = HashMap<String, Runnable>()
 
     fun debounce(identifier: String, millis: Long, r: Runnable): Boolean {
-        if (runnables.containsKey(identifier)) {
         // debounce
-            val old = runnables[identifier]
-            handler.removeCallbacks(old)
-        }
+        cancel(identifier)
+
         insertRunnable(identifier, r, millis)
         return true
     }
@@ -37,6 +35,14 @@ internal class Debouncer(private val handler: Handler) {
         handler.removeCallbacksAndMessages(null)
     }
 
+    fun cancel(identifier: String) {
+        if (runnables.containsKey(identifier)) {
+            val old = runnables[identifier]
+            handler.removeCallbacks(old)
+            runnables.remove(identifier)
+        }
+    }
+
     private fun insertRunnable(identifier: String, r: Runnable, millis: Long) {
         val chained = Runnable {
             handler.post(r)

vector/src/main/java/im/vector/riotx/features/home/room/detail/JumpToBottomViewVisibilityManager.kt

@@ -0,0 +1,77 @@
+/*
+ * Copyright 2020 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package im.vector.riotx.features.home.room.detail
+
+import androidx.recyclerview.widget.LinearLayoutManager
+import androidx.recyclerview.widget.RecyclerView
+import com.google.android.material.floatingactionbutton.FloatingActionButton
+import im.vector.riotx.core.utils.Debouncer
+import timber.log.Timber
+
+/**
+ * Show or hide the jumpToBottomView, depending on the scrolling and if the timeline is displaying the more recent event
+ * - When user scrolls up (i.e. going to the past): hide
+ * - When user scrolls down: show if not displaying last event
+ * - When user stops scrolling: show if not displaying last event
+ */
+class JumpToBottomViewVisibilityManager(
+        private val jumpToBottomView: FloatingActionButton,
+        private val debouncer: Debouncer,
+        recyclerView: RecyclerView,
+        private val layoutManager: LinearLayoutManager) {
+
+    init {
+        recyclerView.addOnScrollListener(object : RecyclerView.OnScrollListener() {
+            override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
+                debouncer.cancel("jump_to_bottom_visibility")
+
+                val scrollingToPast = dy < 0
+
+                if (scrollingToPast) {
+                    jumpToBottomView.hide()
+                } else {
+                    maybeShowJumpToBottomViewVisibility()
+                }
+            }
+
+            override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
+                when (newState) {
+                    RecyclerView.SCROLL_STATE_IDLE     -> {
+                        maybeShowJumpToBottomViewVisibilityWithDelay()
+                    }
+                    RecyclerView.SCROLL_STATE_DRAGGING,
+                    RecyclerView.SCROLL_STATE_SETTLING -> Unit
+                }
+            }
+        })
+    }
+
+    fun maybeShowJumpToBottomViewVisibilityWithDelay() {
+        debouncer.debounce("jump_to_bottom_visibility", 250, Runnable {
+            maybeShowJumpToBottomViewVisibility()
+        })
+    }
+
+    private fun maybeShowJumpToBottomViewVisibility() {
+        Timber.v("First visible: ${layoutManager.findFirstCompletelyVisibleItemPosition()}")
+        if (layoutManager.findFirstVisibleItemPosition() != 0) {
+            jumpToBottomView.show()
+        } else {
+            jumpToBottomView.hide()
+        }
+    }
+}

vector/src/main/java/im/vector/riotx/features/home/room/detail/RoomDetailFragment.kt

@@ -181,6 +181,7 @@ class RoomDetailFragment @Inject constructor(
 
     private lateinit var sharedActionViewModel: MessageSharedActionViewModel
     private lateinit var layoutManager: LinearLayoutManager
+    private lateinit var jumpToBottomViewVisibilityManager: JumpToBottomViewVisibilityManager
     private var modelBuildListener: OnModelBuildFinishedListener? = null
 
     private lateinit var attachmentsHelper: AttachmentsHelper
@@ -312,6 +313,13 @@ class RoomDetailFragment @Inject constructor(
                 }
             }
         }
+
+        jumpToBottomViewVisibilityManager = JumpToBottomViewVisibilityManager(
+                jumpToBottomView,
+                debouncer,
+                recyclerView,
+                layoutManager
+        )
     }
 
     private fun setupJumpToReadMarkerView() {
@@ -474,25 +482,11 @@ class RoomDetailFragment @Inject constructor(
             it.dispatchTo(scrollOnNewMessageCallback)
             it.dispatchTo(scrollOnHighlightedEventCallback)
             updateJumpToReadMarkerViewVisibility()
-            updateJumpToBottomViewVisibility()
+            jumpToBottomViewVisibilityManager.maybeShowJumpToBottomViewVisibilityWithDelay()
         }
         timelineEventController.addModelBuildListener(modelBuildListener)
         recyclerView.adapter = timelineEventController.adapter
 
-        recyclerView.addOnScrollListener(object : RecyclerView.OnScrollListener() {
-            override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
-                when (newState) {
-                    RecyclerView.SCROLL_STATE_IDLE     -> {
-                        updateJumpToBottomViewVisibility()
-                    }
-                    RecyclerView.SCROLL_STATE_DRAGGING,
-                    RecyclerView.SCROLL_STATE_SETTLING -> {
-                        jumpToBottomView.hide()
-                    }
-                }
-            }
-        })
-
         timelineEventController.callback = this
 
         if (vectorPreferences.swipeToReplyIsEnabled()) {
@@ -547,17 +541,6 @@ class RoomDetailFragment @Inject constructor(
         }
     }
 
-    private fun updateJumpToBottomViewVisibility() {
-        debouncer.debounce("jump_to_bottom_visibility", 250, Runnable {
-            Timber.v("First visible: ${layoutManager.findFirstCompletelyVisibleItemPosition()}")
-            if (layoutManager.findFirstVisibleItemPosition() != 0) {
-                jumpToBottomView.show()
-            } else {
-                jumpToBottomView.hide()
-            }
-        })
-    }
-
     private fun setupComposer() {
         autoCompleter.setup(composerLayout.composerEditText, this)