Improve tab layout animation. Fixes #800 and #801

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

@@ -31,12 +31,14 @@ import eu.kanade.tachiyomi.ui.base.controller.NucleusController
 import eu.kanade.tachiyomi.ui.base.controller.SecondaryDrawerController
 import eu.kanade.tachiyomi.ui.base.controller.TabbedController
 import eu.kanade.tachiyomi.ui.category.CategoryController
+import eu.kanade.tachiyomi.ui.main.MainActivity
 import eu.kanade.tachiyomi.ui.manga.MangaController
 import eu.kanade.tachiyomi.util.inflate
 import eu.kanade.tachiyomi.util.toast
 import eu.kanade.tachiyomi.widget.DrawerSwipeCloseListener
 import kotlinx.android.synthetic.main.activity_main.*
 import kotlinx.android.synthetic.main.library_controller.view.*
+import rx.Subscription
 import timber.log.Timber
 import uy.kohesive.injekt.Injekt
 import uy.kohesive.injekt.api.get
@@ -118,6 +120,10 @@ class LibraryController(
      */
     private var drawerListener: DrawerLayout.DrawerListener? = null
 
+    private var tabsVisibilityRelay: BehaviorRelay<Boolean> = BehaviorRelay.create()
+
+    private var tabsVisibilitySubscription: Subscription? = null
+
     init {
         setHasOptionsMenu(true)
     }
@@ -173,6 +179,8 @@ class LibraryController(
         super.onDestroyView(view)
         adapter = null
         actionMode = null
+        tabsVisibilitySubscription?.unsubscribe()
+        tabsVisibilitySubscription = null
     }
 
     override fun createSecondaryDrawer(drawer: DrawerLayout): ViewGroup {
@@ -204,6 +212,27 @@ class LibraryController(
         navView = null
     }
 
+    override fun configureTabs(tabs: TabLayout) {
+        with(tabs) {
+            tabGravity = TabLayout.GRAVITY_CENTER
+            tabMode = TabLayout.MODE_SCROLLABLE
+        }
+        tabsVisibilitySubscription?.unsubscribe()
+        tabsVisibilitySubscription = tabsVisibilityRelay.subscribe { visible ->
+            val tabAnimator = (activity as? MainActivity)?.tabAnimator
+            if (visible) {
+                tabAnimator?.expand()
+            } else {
+                tabAnimator?.collapse()
+            }
+        }
+    }
+
+    override fun cleanupTabs(tabs: TabLayout) {
+        tabsVisibilitySubscription?.unsubscribe()
+        tabsVisibilitySubscription = null
+    }
+
     fun onNextLibraryUpdate(categories: List<Category>, mangaMap: Map<Int, List<LibraryItem>>) {
         val view = view ?: return
         val adapter = adapter ?: return
@@ -227,7 +256,7 @@ class LibraryController(
         // Restore active category.
         view.view_pager.setCurrentItem(activeCat, false)
 
-        tabs?.visibility = if (categories.size <= 1) View.GONE else View.VISIBLE
+        tabsVisibilityRelay.call(categories.size > 1)
 
         // Delay the scroll position to allow the view to be properly measured.
         view.post {
@@ -282,13 +311,6 @@ class LibraryController(
         adapter.recycle = true
     }
 
-    override fun configureTabs(tabs: TabLayout) {
-        with(tabs) {
-            tabGravity = TabLayout.GRAVITY_CENTER
-            tabMode = TabLayout.MODE_SCROLLABLE
-        }
-    }
-
     /**
      * Creates the action mode if it's not created already.
      */

app/src/main/java/eu/kanade/tachiyomi/ui/main/MainActivity.kt

@@ -49,7 +49,7 @@ class MainActivity : BaseActivity() {
         }
     }
 
-    private val tabAnimator by lazy { TabsAnimator(tabs) }
+    lateinit var tabAnimator: TabsAnimator
 
     override fun onCreate(savedInstanceState: Bundle?) {
         setAppTheme()
@@ -69,6 +69,8 @@ class MainActivity : BaseActivity() {
         drawerArrow?.color = Color.WHITE
         toolbar.navigationIcon = drawerArrow
 
+        tabAnimator = TabsAnimator(tabs)
+
         // Set behavior of Navigation drawer
         nav_view.setNavigationItemSelectedListener { item ->
             val id = item.itemId
@@ -190,8 +192,8 @@ class MainActivity : BaseActivity() {
             from.cleanupTabs(tabs)
         }
         if (to is TabbedController) {
-            to.configureTabs(tabs)
             tabAnimator.expand()
+            to.configureTabs(tabs)
         } else {
             tabAnimator.collapse()
             tabs.setupWithViewPager(null)

app/src/main/java/eu/kanade/tachiyomi/ui/main/TabsAnimator.kt

@@ -1,6 +1,8 @@
 package eu.kanade.tachiyomi.ui.main
 
 import android.support.design.widget.TabLayout
+import android.view.View
+import android.view.ViewTreeObserver
 import android.view.animation.Animation
 import android.view.animation.DecelerateInterpolator
 import android.view.animation.Transformation
@@ -9,15 +11,32 @@ import eu.kanade.tachiyomi.util.visible
 
 class TabsAnimator(val tabs: TabLayout) {
 
-    private var height = 0
+    /**
+     * The default height of the tab layout. It's unknown until the view is layout.
+     */
+    private var tabsHeight = 0
 
+    /**
+     * Whether the last state of the tab layout is [View.VISIBLE] or [View.GONE].
+     */
+    private var isLastStateShown = true
+
+    /**
+     * Interpolator used to animate the tab layout.
+     */
     private val interpolator = DecelerateInterpolator()
 
+    /**
+     * Duration of the animation.
+     */
     private val duration = 300L
 
+    /**
+     * Animation used to expand the tab layout.
+     */
     private val expandAnimation = object : Animation() {
         override fun applyTransformation(interpolatedTime: Float, t: Transformation) {
-            tabs.layoutParams.height = (height * interpolatedTime).toInt()
+            setHeight((tabsHeight * interpolatedTime).toInt())
             tabs.requestLayout()
         }
 
@@ -26,12 +45,24 @@ class TabsAnimator(val tabs: TabLayout) {
         }
     }
 
+    /**
+     * Animation used to collapse the tab layout.
+     */
     private val collapseAnimation = object : Animation() {
+
+        /**
+         * Property holding the height of the tabs at the moment the animation is started. Useful
+         * to provide a seamless animation.
+         */
+        private var startHeight = 0
+
         override fun applyTransformation(interpolatedTime: Float, t: Transformation) {
-            if (interpolatedTime == 1f) {
+            if (interpolatedTime == 0f) {
+                startHeight = tabs.height
+            } else if (interpolatedTime == 1f) {
                 tabs.gone()
             } else {
-                tabs.layoutParams.height = (height * (1 - interpolatedTime)).toInt()
+                setHeight((startHeight * (1 - interpolatedTime)).toInt())
                 tabs.requestLayout()
             }
         }
@@ -46,29 +77,75 @@ class TabsAnimator(val tabs: TabLayout) {
         collapseAnimation.interpolator = interpolator
         expandAnimation.duration = duration
         expandAnimation.interpolator = interpolator
-    }
 
-    fun expand() {
+        isLastStateShown = tabs.visibility == View.VISIBLE
+        tabs.viewTreeObserver.addOnGlobalLayoutListener(
+            object : ViewTreeObserver.OnGlobalLayoutListener {
+                override fun onGlobalLayout() {
+                    if (tabs.height > 0) {
+                        tabs.viewTreeObserver.removeOnGlobalLayoutListener(this)
+
+                        // Save the tabs default height.
+                        tabsHeight = tabs.height
+
+                        // Now that we know the height, set the initial height and visibility.
+                        if (isLastStateShown) {
+                            setHeight(tabsHeight)
                             tabs.visible()
-        if (measure() && tabs.measuredHeight != height) {
-            tabs.startAnimation(expandAnimation)
-        }
-    }
-
-    fun collapse() {
-        if (measure() && tabs.measuredHeight != 0) {
-            tabs.startAnimation(collapseAnimation)
                         } else {
+                            setHeight(0)
                             tabs.gone()
                         }
                     }
+                }
+            }
+        )
+    }
 
     /**
-     * Returns true if the view is measured, otherwise query dimensions and check again.
+     * Sets the height of the tab layout.
+     *
+     * @param newHeight The new height of the tab layout.
      */
-    private fun measure(): Boolean {
+    private fun setHeight(newHeight: Int) {
-        if (height > 0) return true
+        tabs.layoutParams.height = newHeight
-        height = tabs.measuredHeight
-        return height > 0
     }
+
+    /**
+     * Expands the tab layout with an animation.
+     */
+    fun expand() {
+        cancelCurrentAnimations()
+        tabs.visible()
+        if (isMeasured && (!isLastStateShown || tabs.height != tabsHeight)) {
+            tabs.startAnimation(expandAnimation)
+        }
+        isLastStateShown = true
+    }
+
+    /**
+     * Collapse the tab layout with an animation.
+     */
+    fun collapse() {
+        cancelCurrentAnimations()
+        if (isMeasured && (isLastStateShown || tabs.height != 0)) {
+            tabs.startAnimation(collapseAnimation)
+        }
+        isLastStateShown = false
+    }
+
+    /**
+     * Cancels all the currently running animations.
+     */
+    private fun cancelCurrentAnimations() {
+        collapseAnimation.cancel()
+        expandAnimation.cancel()
+    }
+
+    /**
+     * Returns whether the tab layout has a known height.
+     */
+    val isMeasured: Boolean
+        get() = tabsHeight > 0
+
 }

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

@@ -24,7 +24,6 @@
                 android:id="@+id/tabs"
                 android:layout_width="match_parent"
                 android:layout_height="wrap_content"
-                android:visibility="gone"
                 android:theme="@style/Theme.ActionBar.Tab"
                 app:tabIndicatorColor="@android:color/white"
                 app:tabGravity="center"