Fixed weird behavior with dragging categories

app/src/main/java/eu/kanade/tachiyomi/ui/category/CategoryController.kt

@@ -15,7 +15,7 @@ import eu.kanade.tachiyomi.ui.base.controller.BaseController
 import eu.kanade.tachiyomi.ui.category.CategoryPresenter.Companion.CREATE_CATEGORY_ORDER
 import eu.kanade.tachiyomi.ui.main.MainActivity
 import eu.kanade.tachiyomi.util.system.toast
-import eu.kanade.tachiyomi.util.view.scrollViewWith
+import eu.kanade.tachiyomi.util.view.liftAppbarWith
 import eu.kanade.tachiyomi.util.view.snack
 import kotlinx.android.synthetic.main.categories_controller.*
 
@@ -66,7 +66,7 @@ class CategoryController(bundle: Bundle? = null) : BaseController(bundle),
      */
     override fun onViewCreated(view: View) {
         super.onViewCreated(view)
-        scrollViewWith(recycler, padBottom = true)
+        liftAppbarWith(recycler)
 
         adapter = CategoryAdapter(this@CategoryController)
         recycler.layoutManager = LinearLayoutManager(view.context)

app/src/main/java/eu/kanade/tachiyomi/ui/category/CategoryPresenter.kt

@@ -4,8 +4,10 @@ import eu.kanade.tachiyomi.R
 import eu.kanade.tachiyomi.data.database.DatabaseHelper
 import eu.kanade.tachiyomi.data.database.models.Category
 import eu.kanade.tachiyomi.data.preference.PreferencesHelper
+import eu.kanade.tachiyomi.util.system.executeOnIO
+import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
-import kotlinx.coroutines.GlobalScope
+import kotlinx.coroutines.Job
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.withContext
 import uy.kohesive.injekt.Injekt
@@ -22,6 +24,8 @@ class CategoryPresenter(
 
     private val context = preferences.context
 
+    private var scope = CoroutineScope(Job() + Dispatchers.Default)
+
     /**
      * List containing categories.
      */
@@ -34,7 +38,7 @@ class CategoryPresenter(
         if (categories.isNotEmpty()) {
             controller.setCategories(categories.map(::CategoryItem))
         }
-        GlobalScope.launch(Dispatchers.IO) {
+        scope.launch(Dispatchers.IO) {
             categories.clear()
             categories.add(newCategory())
             categories.addAll(db.getCategories().executeAsBlocking())
@@ -98,13 +102,16 @@ class CategoryPresenter(
      * @param categories The list of categories to reorder.
      */
     fun reorderCategories(categories: List<Category>) {
-        categories.forEachIndexed { i, category ->
-            if (category.order != CREATE_CATEGORY_ORDER)
-                category.order = i - 1
+        scope.launch {
+            categories.forEachIndexed { i, category ->
+                if (category.order != CREATE_CATEGORY_ORDER) category.order = i - 1
+            }
+            db.insertCategories(categories.filter { it.order != CREATE_CATEGORY_ORDER }).executeOnIO()
+            this@CategoryPresenter.categories = categories.sortedBy { it.order }.toMutableList()
+            withContext(Dispatchers.Main) {
+                controller.setCategories(this@CategoryPresenter.categories.map(::CategoryItem))
+            }
         }
-        db.insertCategories(categories.filter { it.order != CREATE_CATEGORY_ORDER }).executeAsBlocking()
-        this.categories = categories.sortedBy { it.order }.toMutableList()
-        controller.setCategories(categories.map(::CategoryItem))
     }
 
     /**

app/src/main/java/eu/kanade/tachiyomi/util/view/ControllerExtensions.kt

@@ -55,6 +55,37 @@ fun Controller.setOnQueryTextChangeListener(
     })
 }
 
+fun Controller.liftAppbarWith(recycler: RecyclerView) {
+    view?.applyWindowInsetsForController()
+    recycler.setOnApplyWindowInsetsListener(RecyclerWindowInsetsListener)
+
+    var elevationAnim: ValueAnimator? = null
+    var elevate = false
+    val elevateFunc: (Boolean) -> Unit = { el ->
+        elevate = el
+        elevationAnim?.cancel()
+        elevationAnim = ValueAnimator.ofFloat(
+            activity?.appbar?.elevation ?: 0f, if (el) 15f else 0f
+        )
+        elevationAnim?.addUpdateListener { valueAnimator ->
+            activity?.appbar?.elevation = valueAnimator.animatedValue as Float
+        }
+        elevationAnim?.start()
+    }
+    elevateFunc(recycler.canScrollVertically(-1))
+    recycler.addOnScrollListener(object : RecyclerView.OnScrollListener() {
+        override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
+            super.onScrolled(recyclerView, dx, dy)
+            if (router?.backstack?.lastOrNull()
+                    ?.controller() == this@liftAppbarWith && activity != null
+            ) {
+                val notAtTop = recycler.canScrollVertically(-1)
+                if (notAtTop != elevate) elevateFunc(notAtTop)
+            }
+        }
+    })
+}
+
 fun Controller.scrollViewWith(
     recycler: RecyclerView,
     padBottom: Boolean = false,