Merge pull request #52 from st235/fix/scrolling_behaviour

fixed scrolling behaviour for corrdinator layout.

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

@@ -1,32 +1,30 @@
 <?xml version="1.0" encoding="utf-8"?>
-<androidx.coordinatorlayout.widget.CoordinatorLayout
-        xmlns:android="http://schemas.android.com/apk/res/android"
-        xmlns:app="http://schemas.android.com/apk/res-auto"
-        xmlns:tools="http://schemas.android.com/tools"
-        android:layout_width="match_parent"
-        android:layout_height="match_parent"
-        tools:context="github.com.st235.expandablebottombar.screens.CoordinatorLayoutActivity">
+<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    tools:context="github.com.st235.expandablebottombar.screens.CoordinatorLayoutActivity">
 
     <androidx.recyclerview.widget.RecyclerView
-            android:id="@+id/recycler_view"
-            android:layout_width="match_parent"
-            android:layout_height="match_parent"
-            />
+        android:id="@+id/recycler_view"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent" />
 
     <com.google.android.material.floatingactionbutton.FloatingActionButton
-            android:id="@+id/fab"
-            android:layout_width="wrap_content"
-            android:layout_height="wrap_content"
-            android:layout_gravity="bottom|end"
-            android:layout_margin="16dp"
-            app:srcCompat="@drawable/ic_meow"/>
+        android:id="@+id/fab"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="bottom|end"
+        android:layout_margin="16dp"
+        app:srcCompat="@drawable/ic_meow" />
 
     <github.com.st235.lib_expandablebottombar.ExpandableBottomBar
-            android:id="@+id/expandable_bottom_bar"
-            android:layout_width="match_parent"
-            android:layout_height="wrap_content"
-            android:layout_gravity="bottom"
-            app:layout_behavior="github.com.st235.lib_expandablebottombar.behavior.ExpandableBottomBarScrollableBehavior"
-            app:exb_items="@menu/bottom_bar" />
+        android:id="@+id/expandable_bottom_bar"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:layout_gravity="bottom"
+        app:exb_items="@menu/bottom_bar"
+        app:layout_behavior="github.com.st235.lib_expandablebottombar.behavior.ExpandableBottomBarScrollableBehavior" />
 
 </androidx.coordinatorlayout.widget.CoordinatorLayout>

build.gradle

@@ -1,7 +1,7 @@
 ext {
     vers = [
-            versionCode: 35,
-            versionName: "1.2.2"
+            versionCode: 36,
+            versionName: "1.2.3"
     ]
     info = [
             name: 'expandablebottombar',

lib-expandablebottombar/src/main/java/github/com/st235/lib_expandablebottombar/behavior/ExpandableBottomBarScrollableBehavior.kt

@@ -1,15 +1,27 @@
 package github.com.st235.lib_expandablebottombar.behavior
 
+import android.animation.ValueAnimator
 import android.content.Context
+import android.os.Handler
+import android.os.Looper
 import android.util.AttributeSet
 import android.view.View
+import android.view.animation.DecelerateInterpolator
 import androidx.coordinatorlayout.widget.CoordinatorLayout
 import androidx.core.view.ViewCompat
+import androidx.core.view.marginBottom
 import github.com.st235.lib_expandablebottombar.utils.clamp
+import kotlin.math.abs
 
 class ExpandableBottomBarScrollableBehavior<V: View>:
     ExpandableBottomBarBehavior<V> {
 
+    private val handler = Handler(Looper.getMainLooper())
+    private var lastKnownRunnable: Runnable? = null
+
+    private var animator: ValueAnimator? = null
+    private var lastKnownDirection: Int? = null
+
     constructor(): super()
 
     constructor(context: Context, attributeSet: AttributeSet): super(context, attributeSet)
@@ -20,10 +32,77 @@ class ExpandableBottomBarScrollableBehavior<V: View>:
         return axes == ViewCompat.SCROLL_AXIS_VERTICAL
     }
 
-    override fun onNestedPreScroll(
-        coordinatorLayout: CoordinatorLayout, child: V, target: View, dx: Int, dy: Int, consumed: IntArray, type: Int
-    ) {
-        super.onNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed, type)
-        child.translationY = clamp(child.translationY + dy, 0f, child.height.toFloat())
+    override fun onNestedScroll(coordinatorLayout: CoordinatorLayout, child: V, target: View, dxConsumed: Int, dyConsumed: Int, dxUnconsumed: Int, dyUnconsumed: Int, type: Int, consumed: IntArray) {
+        super.onNestedScroll(coordinatorLayout, child, target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, type, consumed)
+
+        if (lastKnownRunnable != null) {
+            handler.removeCallbacks(lastKnownRunnable)
+            lastKnownRunnable = null
+        }
+
+        cancelAnimation()
+
+        lastKnownDirection = dyConsumed
+        child.translationY = getScrollRange(child, dyConsumed)
+    }
+
+    override fun onStopNestedScroll(coordinatorLayout: CoordinatorLayout, child: V, target: View, type: Int) {
+        super.onStopNestedScroll(coordinatorLayout, child, target, type)
+
+        if (lastKnownRunnable != null) {
+            handler.removeCallbacks(lastKnownRunnable)
+        }
+
+        lastKnownRunnable = Runnable {
+            animateWithDirection(child)
+        }
+        handler.postDelayed(lastKnownRunnable, 500L)
+    }
+
+    private fun getScrollRange(child: V, dy: Int): Float {
+        return clamp(child.translationY + dy, 0f, getMaxScrollDistance(child))
+    }
+
+    private fun getMaxScrollDistance(child: V): Float {
+        val childHeight = if (ViewCompat.isLaidOut(child)) child.height else child.measuredHeight
+        return childHeight.toFloat() + child.marginBottom
+    }
+
+    private fun animateWithDirection(child: V) {
+        val dy = lastKnownDirection ?: return
+        val halfOfScrollDistance = getMaxScrollDistance(child) / 2F
+
+        val overHalfUp = dy < 0 /* up */ && abs(child.translationY) < halfOfScrollDistance
+        val lessThanHalfDown = dy > 0 /* down */ && abs(child.translationY) < halfOfScrollDistance
+
+        if (overHalfUp || lessThanHalfDown) {
+            animateTo(child, 0F)
+        } else {
+            animateTo(child, getMaxScrollDistance(child))
+        }
+    }
+
+    private fun animateTo(child: V, translation: Float) {
+        if (child.translationY == 0F || child.translationY == getMaxScrollDistance(child)) {
+            return
+        }
+
+        cancelAnimation()
+
+        animator = ValueAnimator.ofFloat(child.translationY, translation)
+        animator?.interpolator = DecelerateInterpolator()
+        animator?.addUpdateListener { animator ->
+            val animatedValue = this.animator?.animatedValue as Float
+            child.translationY = animatedValue
+        }
+
+        animator?.start()
+    }
+
+    private fun cancelAnimation() {
+        if (animator != null && animator?.isRunning == true) {
+            animator?.cancel()
+            animator = null
+        }
     }
 }