resolves #99

app/build.gradle

@@ -77,6 +77,7 @@ dependencies {
     implementation ("com.github.bumptech.glide:recyclerview-integration:4.11.0") {
         transitive = false
     }
+    implementation 'com.tbuonomo.andrui:viewpagerdotsindicator:4.1.2'
     implementation 'net.rdrei.android.dirchooser:library:3.2@aar'
     implementation 'com.github.chrisbanes:PhotoView:2.3.0'
     implementation 'com.andrognito.patternlockview:patternlockview:1.0.0'

app/src/main/java/xyz/quaver/pupil/adapters/ThumbnailAdapter.kt

@@ -22,9 +22,10 @@ import android.view.ViewGroup
 import android.widget.ImageView
 import androidx.recyclerview.widget.RecyclerView
 import com.bumptech.glide.RequestManager
+import com.bumptech.glide.load.engine.DiskCacheStrategy
 import xyz.quaver.pupil.BuildConfig
 
-class ThumbnailAdapter(private val glide: RequestManager, private val thumbnails: List<String>) : RecyclerView.Adapter<ThumbnailAdapter.ViewHolder>() {
+class ThumbnailAdapter(private val glide: RequestManager, var thumbnails: List<String>) : RecyclerView.Adapter<ThumbnailAdapter.ViewHolder>() {
 
     class ViewHolder(val view: ImageView) : RecyclerView.ViewHolder(view)
 
@@ -35,6 +36,7 @@ class ThumbnailAdapter(private val glide: RequestManager, private val thumbnails
     override fun onBindViewHolder(holder: ViewHolder, position: Int) {
         glide
             .load(thumbnails[position])
+            .diskCacheStrategy(DiskCacheStrategy.NONE)
             .apply {
                 if (BuildConfig.CENSOR)
                     override(5, 8)

app/src/main/java/xyz/quaver/pupil/adapters/ThumbnailPageAdapter.kt

@@ -0,0 +1,50 @@
+/*
+ *     Pupil, Hitomi.la viewer for Android
+ *     Copyright (C) 2020  tom5079
+ *
+ *     This program is free software: you can redistribute it and/or modify
+ *     it under the terms of the GNU General Public License as published by
+ *     the Free Software Foundation, either version 3 of the License, or
+ *     (at your option) any later version.
+ *
+ *     This program is distributed in the hope that it will be useful,
+ *     but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *     GNU General Public License for more details.
+ *
+ *     You should have received a copy of the GNU General Public License
+ *     along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package xyz.quaver.pupil.adapters
+
+import android.view.ViewGroup
+import androidx.recyclerview.widget.GridLayoutManager
+import androidx.recyclerview.widget.RecyclerView
+import com.bumptech.glide.RequestManager
+import kotlin.math.min
+
+class ThumbnailPageAdapter(private val glide: RequestManager, private val thumbnails: List<String>) : RecyclerView.Adapter<ThumbnailPageAdapter.ViewHolder>() {
+
+    class ViewHolder(val view: RecyclerView) : RecyclerView.ViewHolder(view)
+
+    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
+        return ViewHolder(RecyclerView(parent.context).apply {
+            layoutManager = GridLayoutManager(parent.context, 3)
+            adapter = ThumbnailAdapter(glide, listOf())
+            layoutParams = ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT)
+        })
+    }
+
+    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
+        (holder.view.adapter as ThumbnailAdapter).apply {
+            thumbnails = this@ThumbnailPageAdapter.thumbnails.slice(9*position until min(9*position+9, this@ThumbnailPageAdapter.thumbnails.size))
+            notifyDataSetChanged()
+
+            holder.view.layoutManager?.scrollToPosition(itemCount-1)
+        }
+    }
+
+    override fun getItemCount() = if (thumbnails.isEmpty()) 0 else thumbnails.size/9 + if (thumbnails.size%9 != 0) 1 else 0
+
+}

app/src/main/java/xyz/quaver/pupil/ui/dialog/GalleryDialog.kt

@@ -26,14 +26,15 @@ import android.view.LayoutInflater
 import android.view.View
 import android.widget.LinearLayout.LayoutParams
 import androidx.core.content.ContextCompat
-import androidx.recyclerview.widget.GridLayoutManager
 import androidx.recyclerview.widget.LinearLayoutManager
 import androidx.recyclerview.widget.RecyclerView
+import androidx.viewpager2.widget.ViewPager2
 import com.bumptech.glide.RequestManager
 import com.google.android.material.chip.Chip
 import com.google.android.material.snackbar.Snackbar
 import kotlinx.android.synthetic.main.dialog_gallery.*
-import kotlinx.android.synthetic.main.gallery_details.view.*
+import kotlinx.android.synthetic.main.dialog_gallery_details.view.*
+import kotlinx.android.synthetic.main.dialog_gallery_dotindicator.view.*
 import kotlinx.android.synthetic.main.item_gallery_details.view.*
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
@@ -46,7 +47,7 @@ import xyz.quaver.pupil.BuildConfig
 import xyz.quaver.pupil.Pupil
 import xyz.quaver.pupil.R
 import xyz.quaver.pupil.adapters.GalleryBlockAdapter
-import xyz.quaver.pupil.adapters.ThumbnailAdapter
+import xyz.quaver.pupil.adapters.ThumbnailPageAdapter
 import xyz.quaver.pupil.types.Tag
 import xyz.quaver.pupil.ui.ReaderActivity
 import xyz.quaver.pupil.util.ItemClickSupport
@@ -130,7 +131,7 @@ class GalleryDialog(context: Context, private val glide: RequestManager, private
     private fun addDetails(gallery: Gallery) {
         val inflater = LayoutInflater.from(context)
         
-        inflater.inflate(R.layout.gallery_details, gallery_contents, false).apply {
+        inflater.inflate(R.layout.dialog_gallery_details, gallery_contents, false).apply {
             gallery_details.setText(R.string.gallery_details)
 
             listOf(
@@ -206,15 +207,21 @@ class GalleryDialog(context: Context, private val glide: RequestManager, private
     private fun addThumbnails(gallery: Gallery) {
         val inflater = LayoutInflater.from(context)
 
-        inflater.inflate(R.layout.gallery_details, gallery_contents, false).apply {
+        inflater.inflate(R.layout.dialog_gallery_details, gallery_contents, false).apply {
             gallery_details.setText(R.string.gallery_thumbnails)
 
-            RecyclerView(context).apply {
+            val pager = ViewPager2(context).apply {
-                layoutManager = GridLayoutManager(context, 3)
+                adapter = ThumbnailPageAdapter(glide, gallery.thumbnails)
-                adapter = ThumbnailAdapter(glide, gallery.thumbnails)
-            }.let {
-                gallery_details_contents.addView(it, LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT))
             }
+
+            gallery_details_contents.addView(
+                pager,
+                LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT)
+            )
+
+            LayoutInflater.from(context).inflate(R.layout.dialog_gallery_dotindicator, gallery_details_contents)
+
+            gallery_dotindicator.setViewPager2(pager)
         }.let {
             gallery_contents.addView(it)
         }
@@ -245,7 +252,7 @@ class GalleryDialog(context: Context, private val glide: RequestManager, private
             }
         }
 
-        inflater.inflate(R.layout.gallery_details, gallery_contents, false).apply {
+        inflater.inflate(R.layout.dialog_gallery_details, gallery_contents, false).apply {
             gallery_details.setText(R.string.gallery_related)
 
             RecyclerView(context).apply {

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

@@ -0,0 +1,34 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  ~     Pupil, Hitomi.la viewer for Android
+  ~     Copyright (C) 2020  tom5079
+  ~
+  ~     This program is free software: you can redistribute it and/or modify
+  ~     it under the terms of the GNU General Public License as published by
+  ~     the Free Software Foundation, either version 3 of the License, or
+  ~     (at your option) any later version.
+  ~
+  ~     This program is distributed in the hope that it will be useful,
+  ~     but WITHOUT ANY WARRANTY; without even the implied warranty of
+  ~     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  ~     GNU General Public License for more details.
+  ~
+  ~     You should have received a copy of the GNU General Public License
+  ~     along with this program.  If not, see <http://www.gnu.org/licenses/>.
+  -->
+
+<RelativeLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:layout_margin="8dp">
+
+    <com.tbuonomo.viewpagerdotsindicator.DotsIndicator
+        android:id="@+id/gallery_dotindicator"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_centerHorizontal="true"
+        app:dotsSize="8dp"/>
+
+</RelativeLayout>