Revert ViewPager2 library

app/build.gradle

@@ -143,7 +143,6 @@ dependencies {
     implementation 'androidx.preference:preference:1.1.1'
     implementation 'androidx.recyclerview:recyclerview:1.2.0-alpha04'
     implementation 'androidx.swiperefreshlayout:swiperefreshlayout:1.1.0'
-    implementation "androidx.viewpager2:viewpager2:1.0.0"
     implementation 'androidx.webkit:webkit:1.3.0-rc01'
 
     final lifecycle_version = '2.3.0-alpha05'
@@ -236,6 +235,7 @@ dependencies {
     implementation 'eu.davidea:flexible-adapter:5.1.0'
     implementation 'eu.davidea:flexible-adapter-ui:1.0.0'
     implementation 'com.nononsenseapps:filepicker:2.5.2'
+    implementation 'com.nightlynexus.viewstatepageradapter:viewstatepageradapter:1.1.0'
     implementation 'com.github.mthli:Slice:v1.3'
     implementation 'com.github.chrisbanes:PhotoView:2.3.0'
     implementation 'com.github.carlosesco:DirectionalViewPager:a844dbca0a'
@@ -259,7 +259,7 @@ dependencies {
     implementation "io.github.reactivecircus.flowbinding:flowbinding-appcompat:$flowbinding_version"
     implementation "io.github.reactivecircus.flowbinding:flowbinding-recyclerview:$flowbinding_version"
     implementation "io.github.reactivecircus.flowbinding:flowbinding-swiperefreshlayout:$flowbinding_version"
-    implementation "io.github.reactivecircus.flowbinding:flowbinding-viewpager2:$flowbinding_version"
+    implementation "io.github.reactivecircus.flowbinding:flowbinding-viewpager:$flowbinding_version"
 
     // Licenses
     final aboutlibraries_version = '8.2.0'

app/src/main/java/eu/kanade/tachiyomi/ui/library/LibraryAdapter.kt

@@ -1,20 +1,18 @@
 package eu.kanade.tachiyomi.ui.library
 
-import android.content.Context
-import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
-import androidx.recyclerview.widget.RecyclerView
+import eu.kanade.tachiyomi.R
 import eu.kanade.tachiyomi.data.database.models.Category
-import eu.kanade.tachiyomi.databinding.LibraryCategoryBinding
+import eu.kanade.tachiyomi.util.view.inflate
+import eu.kanade.tachiyomi.widget.RecyclerViewPagerAdapter
 
 /**
  * This adapter stores the categories from the library, used with a ViewPager.
+ *
+ * @constructor creates an instance of the adapter.
  */
-class LibraryAdapter(
-    private val context: Context,
-    private val controller: LibraryController
-) : RecyclerView.Adapter<LibraryAdapter.ViewHolder>() {
+class LibraryAdapter(private val controller: LibraryController) : RecyclerViewPagerAdapter() {
 
     /**
      * The categories to bind in the adapter.
@@ -30,25 +28,45 @@ class LibraryAdapter(
 
     private var boundViews = arrayListOf<View>()
 
-    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
-        val binding = LibraryCategoryBinding.inflate(LayoutInflater.from(context), parent, false)
-        binding.root.onCreate(controller)
-        return ViewHolder(binding)
+    /**
+     * Creates a new view for this adapter.
+     *
+     * @return a new view.
+     */
+    override fun createView(container: ViewGroup): View {
+        val view = container.inflate(R.layout.library_category) as LibraryCategoryView
+        view.onCreate(controller)
+        return view
     }
 
-    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
-        val view = (holder.itemView as LibraryCategoryView)
-        view.onBind(categories[position])
+    /**
+     * Binds a view with a position.
+     *
+     * @param view the view to bind.
+     * @param position the position in the adapter.
+     */
+    override fun bindView(view: View, position: Int) {
+        (view as LibraryCategoryView).onBind(categories[position])
         boundViews.add(view)
     }
 
-    override fun onViewRecycled(holder: ViewHolder) {
-        val view = (holder.itemView as LibraryCategoryView)
-        view.onRecycle()
+    /**
+     * Recycles a view.
+     *
+     * @param view the view to recycle.
+     * @param position the position in the adapter.
+     */
+    override fun recycleView(view: View, position: Int) {
+        (view as LibraryCategoryView).onRecycle()
         boundViews.remove(view)
     }
 
-    override fun getItemCount(): Int {
+    /**
+     * Returns the number of categories.
+     *
+     * @return the number of categories or 0 if the list is null.
+     */
+    override fun getCount(): Int {
         return categories.size
     }
 
@@ -58,10 +76,19 @@ class LibraryAdapter(
      * @param position the position of the element.
      * @return the title to display.
      */
-    fun getPageTitle(position: Int): CharSequence {
+    override fun getPageTitle(position: Int): CharSequence {
         return categories[position].name
     }
 
+    /**
+     * Returns the position of the view.
+     */
+    override fun getItemPosition(obj: Any): Int {
+        val view = obj as? LibraryCategoryView ?: return POSITION_NONE
+        val index = categories.indexOfFirst { it.id == view.category.id }
+        return if (index == -1) POSITION_NONE else index
+    }
+
     /**
      * Called when the view of this adapter is being destroyed.
      */
@@ -72,6 +99,4 @@ class LibraryAdapter(
             }
         }
     }
-
-    class ViewHolder(binding: LibraryCategoryBinding) : RecyclerView.ViewHolder(binding.root)
 }

app/src/main/java/eu/kanade/tachiyomi/ui/library/LibraryController.kt

@@ -15,7 +15,6 @@ import androidx.core.graphics.drawable.DrawableCompat
 import com.bluelinelabs.conductor.ControllerChangeHandler
 import com.bluelinelabs.conductor.ControllerChangeType
 import com.google.android.material.tabs.TabLayout
-import com.google.android.material.tabs.TabLayoutMediator
 import com.jakewharton.rxrelay.BehaviorRelay
 import com.jakewharton.rxrelay.PublishRelay
 import com.tfcporciuncula.flow.Preference
@@ -46,7 +45,7 @@ import kotlinx.coroutines.flow.launchIn
 import kotlinx.coroutines.flow.onEach
 import reactivecircus.flowbinding.android.view.clicks
 import reactivecircus.flowbinding.appcompat.queryTextChanges
-import reactivecircus.flowbinding.viewpager2.pageSelections
+import reactivecircus.flowbinding.viewpager.pageSelections
 import rx.Subscription
 import uy.kohesive.injekt.Injekt
 import uy.kohesive.injekt.api.get
@@ -165,8 +164,7 @@ class LibraryController(
     override fun onViewCreated(view: View) {
         super.onViewCreated(view)
 
-        adapter = LibraryAdapter(activity!!, this)
-        binding.libraryPager.offscreenPageLimit = 5
+        adapter = LibraryAdapter(this)
         binding.libraryPager.adapter = adapter
         binding.libraryPager.pageSelections()
             .onEach {
@@ -214,11 +212,7 @@ class LibraryController(
     override fun onChangeStarted(handler: ControllerChangeHandler, type: ControllerChangeType) {
         super.onChangeStarted(handler, type)
         if (type.isEnter) {
-            activity?.tabs?.let { tabLayout ->
-                TabLayoutMediator(tabLayout, binding.libraryPager) { tab, position ->
-                    tab.text = adapter?.getPageTitle(position)
-                }.attach()
-            }
+            activity?.tabs?.setupWithViewPager(binding.libraryPager)
             presenter.subscribeLibrary()
         }
     }
@@ -339,8 +333,10 @@ class LibraryController(
 
         val position = binding.libraryPager.currentItem
 
+        adapter.recycle = false
         binding.libraryPager.adapter = adapter
         binding.libraryPager.currentItem = position
+        adapter.recycle = true
     }
 
     /**

app/src/main/java/eu/kanade/tachiyomi/widget/RecyclerViewPagerAdapter.kt

@@ -0,0 +1,34 @@
+package eu.kanade.tachiyomi.widget
+
+import android.view.View
+import android.view.ViewGroup
+import com.nightlynexus.viewstatepageradapter.ViewStatePagerAdapter
+import java.util.Stack
+
+abstract class RecyclerViewPagerAdapter : ViewStatePagerAdapter() {
+
+    private val pool = Stack<View>()
+
+    var recycle = true
+        set(value) {
+            if (!value) pool.clear()
+            field = value
+        }
+
+    protected abstract fun createView(container: ViewGroup): View
+
+    protected abstract fun bindView(view: View, position: Int)
+
+    protected open fun recycleView(view: View, position: Int) {}
+
+    override fun createView(container: ViewGroup, position: Int): View {
+        val view = if (pool.isNotEmpty()) pool.pop() else createView(container)
+        bindView(view, position)
+        return view
+    }
+
+    override fun destroyView(container: ViewGroup, position: Int, view: View) {
+        recycleView(view, position)
+        if (recycle) pool.push(view)
+    }
+}

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

@@ -39,7 +39,7 @@
             tools:text="Search"
             tools:visibility="visible" />
 
-        <androidx.viewpager2.widget.ViewPager2
+        <androidx.viewpager.widget.ViewPager
             android:id="@+id/library_pager"
             android:layout_width="match_parent"
             android:layout_height="match_parent" />