Kotlin version - Fixed AppBarLayout.Behavior for https://issuetracker.google.com/66996774

FixAppBarLayoutBehavior.kt

/*
 * Copyright (C) 2018 The Android Open Source Project
 *
 * 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
 *
 *      http://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 your.package

import android.content.Context
import android.support.design.widget.AppBarLayout
import android.support.design.widget.CoordinatorLayout
import android.support.v4.view.ViewCompat
import android.util.AttributeSet
import android.view.View

/**
 * This is the Kotlin version of implementation which was created with the purpose to fix a
 * bug of app bar layout.
 *
 * The original implementation is hosted https://gist.github.com/chrisbanes/8391b5adb9ee42180893300850ed02f2
 */
class FixAppBarLayoutBehavior : AppBarLayout.Behavior {

    constructor() : super()
    constructor(context: Context, attrs: AttributeSet) : super(context, attrs)

    override fun onNestedScroll(coordinatorLayout: CoordinatorLayout,
                                child: AppBarLayout,
                                target: View,
                                dxConsumed: Int,
                                dyConsumed: Int,
                                dxUnconsumed: Int,
                                dyUnconsumed: Int,
                                type: Int) {
        super.onNestedScroll(coordinatorLayout, child, target, dxConsumed, dyConsumed,
                dxUnconsumed, dyUnconsumed, type)
        stopNestedScrollIfNeeded(dyUnconsumed, child, target, type)
    }

    override fun onNestedPreScroll(coordinatorLayout: CoordinatorLayout,
                                   child: AppBarLayout,
                                   target: View,
                                   dx: Int,
                                   dy: Int,
                                   consumed: IntArray,
                                   type: Int) {
        super.onNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed, type)
        stopNestedScrollIfNeeded(dy, child, target, type)
    }

    private fun stopNestedScrollIfNeeded(dy: Int,
                                         child: AppBarLayout,
                                         target: View,
                                         type: Int) {
        if (type != ViewCompat.TYPE_NON_TOUCH) {
            return
        }

        val currOffset = topAndBottomOffset
        if (dy < 0 && currOffset == 0 || dy > 0 && currOffset == -child.totalScrollRange) {
            ViewCompat.stopNestedScroll(target, ViewCompat.TYPE_NON_TOUCH)
        }
    }
}

Usage.kt

val appBarLayout = findViewById(R.id.app_bar);
(appBarLayout.layoutParams as CoordinatorLayout.LayoutParams).behavior = FixAppBarLayoutBehavior()

usage.xml

<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

    <android.support.design.widget.AppBarLayout
            android:id="@+id/app_bar"
            android:layout_height="..."
            android:layout_width="..."
            app:layout_behavior="your.package.FixAppBarLayoutBehavior">

    </android.support.design.widget.AppBarLayout>

    <!-- Content -->

</android.support.design.widget.CoordinatorLayout>