Animate top level screen transitions.

Change-Id: Ia1134ad5939098a7f0b93f2c137f891e0a1b2e78

Author: nickbutcher

app/src/main/java/com/materialstudies/owl/ui/featured/FeaturedFragment.kt

@@ -20,9 +20,11 @@ import android.os.Bundle
 import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
+import androidx.core.view.postDelayed
 import androidx.fragment.app.Fragment
 import com.materialstudies.owl.databinding.FragmentFeaturedBinding
 import com.materialstudies.owl.model.courses
+import com.materialstudies.owl.util.SpringAddItemAnimator
 
 class FeaturedFragment : Fragment() {
 
@@ -32,8 +34,15 @@ class FeaturedFragment : Fragment() {
         savedInstanceState: Bundle?
     ): View? {
         val binding = FragmentFeaturedBinding.inflate(inflater, container, false).apply {
-            featuredGrid.adapter = FeaturedAdapter().apply {
-                submitList(courses)
+            featuredGrid.apply {
+                itemAnimator = SpringAddItemAnimator()
+                adapter = FeaturedAdapter().apply {
+                    // Add animations not running without this delay
+                    // TODO(nickbutcher) work out why
+                    postDelayed(100L) {
+                        submitList(courses)
+                    }
+                }
             }
         }
         return binding.root

app/src/main/java/com/materialstudies/owl/ui/mycourses/MyCoursesFragment.kt

@@ -17,9 +17,11 @@ import android.os.Bundle
 import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
+import androidx.core.view.postDelayed
 import androidx.fragment.app.Fragment
 import com.materialstudies.owl.databinding.FragmentMyCoursesBinding
 import com.materialstudies.owl.model.courses
+import com.materialstudies.owl.util.SpringAddItemAnimator
 
 class MyCoursesFragment : Fragment() {
 
@@ -29,8 +31,15 @@ class MyCoursesFragment : Fragment() {
         savedInstanceState: Bundle?
     ): View {
         val binding = FragmentMyCoursesBinding.inflate(inflater, container, false).apply {
-            list.adapter = MyCoursesAdapter().apply {
-                submitList(courses)
+            list.apply {
+                itemAnimator = SpringAddItemAnimator()
+                adapter = MyCoursesAdapter().apply {
+                    // Add animations not running without this delay
+                    // TODO(nickbutcher) work out why
+                    postDelayed(100L) {
+                        submitList(courses)
+                    }
+                }
             }
         }
         return binding.root

app/src/main/java/com/materialstudies/owl/ui/search/SearchFragment.kt

@@ -20,9 +20,11 @@ import android.os.Bundle
 import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
+import androidx.core.view.postDelayed
 import androidx.fragment.app.Fragment
 import com.materialstudies.owl.databinding.FragmentSearchBinding
 import com.materialstudies.owl.model.topics
+import com.materialstudies.owl.util.SpringAddItemAnimator
 
 class SearchFragment : Fragment() {
 
@@ -33,8 +35,13 @@ class SearchFragment : Fragment() {
     ): View? {
         val binding = FragmentSearchBinding.inflate(inflater, container, false).apply {
             searchResults.apply {
+                itemAnimator = SpringAddItemAnimator()
                 adapter = SearchAdapter().apply {
-                    submitList(topics)
+                    // Add animations not running without this delay
+                    // TODO(nickbutcher) work out why
+                    postDelayed(100L) {
+                        submitList(topics)
+                    }
                 }
             }
         }

app/src/main/java/com/materialstudies/owl/util/SpringAddItemAnimator.kt

@@ -0,0 +1,120 @@
+/*
+ * Copyright 2019 Google LLC
+ *
+ * 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
+ *
+ *     https://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 com.materialstudies.owl.util
+
+import android.view.View
+import androidx.dynamicanimation.animation.DynamicAnimation
+import androidx.dynamicanimation.animation.SpringAnimation
+import androidx.dynamicanimation.animation.SpringForce
+import androidx.recyclerview.widget.DefaultItemAnimator
+import androidx.recyclerview.widget.RecyclerView
+
+class SpringAddItemAnimator : DefaultItemAnimator() {
+
+    private val pendingAdds = mutableListOf<RecyclerView.ViewHolder>()
+
+    /**
+     * Setup initial values to animate. Derive initial translationY from the view's bottom to
+     * produce a stagger effect, as lower items arrive from father displaced.
+     */
+    override fun animateAdd(holder: RecyclerView.ViewHolder): Boolean {
+        holder.itemView.alpha = 0f
+        holder.itemView.translationY = holder.itemView.bottom / 3f
+        pendingAdds.add(holder)
+        return true
+    }
+
+    /**
+     * Animate back to full alpha and no translation.
+     */
+    override fun runPendingAnimations() {
+        super.runPendingAnimations()
+        if (pendingAdds.isNotEmpty()) {
+            for (i in pendingAdds.indices.reversed()) {
+                val holder = pendingAdds[i]
+
+                val tySpring = holder.itemView.spring(
+                    SpringAnimation.TRANSLATION_Y,
+                    stiffness = 350f,
+                    damping = 0.6f
+                )
+                val aSpring = holder.itemView.spring(
+                    SpringAnimation.ALPHA,
+                    stiffness = 100f,
+                    damping = SpringForce.DAMPING_RATIO_NO_BOUNCY
+                )
+                val endListener = object : DynamicAnimation.OnAnimationEndListener {
+                    override fun onAnimationEnd(
+                        animation: DynamicAnimation<out DynamicAnimation<*>>?,
+                        canceled: Boolean,
+                        value: Float,
+                        velocity: Float
+                    ) {
+                        if (!canceled) {
+                            animation?.removeEndListener(this)
+                            dispatchAddFinished(holder)
+                            dispatchFinishedWhenDone()
+                        } else {
+                            clearAnimatedValues(holder.itemView)
+                        }
+                    }
+                }
+                tySpring.addEndListener(endListener)
+                dispatchAddStarting(holder)
+                aSpring.animateToFinalPosition(1f)
+                tySpring.animateToFinalPosition(0f)
+                pendingAdds.removeAt(i)
+            }
+        }
+    }
+
+    override fun endAnimation(holder: RecyclerView.ViewHolder) {
+        holder.itemView.spring(SpringAnimation.TRANSLATION_Y).cancel()
+        holder.itemView.spring(SpringAnimation.ALPHA).cancel()
+        if (pendingAdds.remove(holder)) {
+            dispatchAddFinished(holder)
+            clearAnimatedValues(holder.itemView)
+        }
+        super.endAnimation(holder)
+    }
+
+    override fun endAnimations() {
+        for (i in pendingAdds.indices.reversed()) {
+            val holder = pendingAdds[i]
+            clearAnimatedValues(holder.itemView)
+            dispatchAddFinished(holder)
+            pendingAdds.removeAt(i)
+        }
+        super.endAnimations()
+    }
+
+    override fun isRunning(): Boolean {
+        return pendingAdds.isNotEmpty() || super.isRunning()
+    }
+
+    private fun dispatchFinishedWhenDone() {
+        if (!isRunning) {
+            dispatchAnimationsFinished()
+        }
+    }
+
+    private fun clearAnimatedValues(view: View) {
+        view.alpha = 1f
+        view.translationY = 0f
+    }
+
+}

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

@@ -34,10 +34,11 @@
       <androidx.appcompat.widget.Toolbar
           android:layout_width="match_parent"
           android:layout_height="wrap_content"
-          android:minHeight="?attr/actionBarSize"
           app:layout_scrollFlags="scroll|enterAlways|snap"
-          app:menu="@menu/account"
-          app:navigationIcon="@drawable/ic_search">
+          android:minHeight="?attr/actionBarSize"
+          app:navigationIcon="@drawable/ic_search"
+          app:contentInsetStartWithNavigation="0dp"
+          app:menu="@menu/account">
 
         <EditText
             android:layout_width="match_parent"
@@ -48,7 +49,7 @@
             android:inputType="textCapWords"
             android:imeOptions="actionSearch"
             android:hint="@string/search_owl"
-            android:textAppearance="?attr/textAppearanceSubtitle1" />
+            android:textAppearance="?attr/textAppearanceSubtitle1"/>
 
       </androidx.appcompat.widget.Toolbar>