android viewpager2 嵌套 recyclerview 手势冲突

老规矩直接上代码， 不分析：

import android.content.Context
import android.util.AttributeSet
import android.view.MotionEvent
import android.view.View
import android.view.ViewConfiguration
import android.view.ViewGroup
import android.widget.FrameLayout
import androidx.recyclerview.widget.RecyclerView
import androidx.viewpager2.widget.ViewPager2
import kotlin.math.abs
import kotlin.math.absoluteValue
import kotlin.math.sign/** Copyright 2019 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.*//*** Layout to wrap a scrollable component inside a ViewPager2. Provided as a solution to the problem* where pages of ViewPager2 have nested scrollable elements that scroll in the same direction as* ViewPager2. The scrollable element needs to be the immediate and only child of this host layout.** This solution has limitations when using multiple levels of nested scrollable elements* (e.g. a horizontal RecyclerView in a vertical RecyclerView in a horizontal ViewPager2).*/
class NestedScrollableHost : FrameLayout {constructor(context: Context) : super(context)constructor(context: Context, attrs: AttributeSet?) : super(context, attrs)private var touchSlop = 0private var initialX = 0fprivate var initialY = 0fprivate val parentViewPager: ViewPager2?get() {var v: View? = parent as? Viewwhile (v != null && v !is ViewPager2) {v = v.parent as? View}return v as? ViewPager2}private val child: View? get() = if (childCount > 0) getChildAt(0) else nullinit {touchSlop = ViewConfiguration.get(context).scaledTouchSlop}private fun canChildScroll(orientation: Int, delta: Float): Boolean {val direction = -delta.sign.toInt()return when (orientation) {0 -> child?.canScrollHorizontally(direction) ?: false1 -> child?.canScrollVertically(direction) ?: falseelse -> throw IllegalArgumentException()}}override fun onInterceptTouchEvent(e: MotionEvent): Boolean {handleInterceptTouchEvent(e)return super.onInterceptTouchEvent(e)}private fun handleInterceptTouchEvent(e: MotionEvent) {val orientation = parentViewPager?.orientation ?: return// Early return if child can't scroll in same direction as parentif (!canChildScroll(orientation, -1f) && !canChildScroll(orientation, 1f)) {return}if (e.action == MotionEvent.ACTION_DOWN) {initialX = e.xinitialY = e.yparent?.requestDisallowInterceptTouchEvent(true)} else if (e.action == MotionEvent.ACTION_MOVE) {val dx = e.x - initialXval dy = e.y - initialYval isVpHorizontal = orientation == RecyclerView.HORIZONTAL// assuming ViewPager2 touch-slop is 2x touch-slop of childval scaledDx = dx.absoluteValue * if (isVpHorizontal) .5f else 1fval scaledDy = dy.absoluteValue * if (isVpHorizontal) 1f else .5fif (scaledDx > touchSlop || scaledDy > touchSlop) {if (isVpHorizontal == (scaledDy > scaledDx)) {// Gesture is perpendicular, allow all parents to interceptparent?.requestDisallowInterceptTouchEvent(false)} else {// Gesture is parallel, query child if movement in that direction is possibleif (canChildScroll(orientation, if (isVpHorizontal) dx else dy)) {// Child can scroll, disallow all parents to interceptparent?.requestDisallowInterceptTouchEvent(true)} else {// Child cannot scroll, allow all parents to interceptparent?.requestDisallowInterceptTouchEvent(false)}}}}}}

/** Copyright 2019 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 androidx.viewpager2.integration.testappimport android.content.Context
import android.util.AttributeSet
import android.view.MotionEvent
import android.view.View
import android.view.ViewConfiguration
import android.widget.FrameLayout
import androidx.viewpager2.widget.ViewPager2
import androidx.viewpager2.widget.ViewPager2.ORIENTATION_HORIZONTAL
import kotlin.math.absoluteValue
import kotlin.math.sign/*** Layout to wrap a scrollable component inside a ViewPager2. Provided as a solution to the problem* where pages of ViewPager2 have nested scrollable elements that scroll in the same direction as* ViewPager2. The scrollable element needs to be the immediate and only child of this host layout.** This solution has limitations when using multiple levels of nested scrollable elements* (e.g. a horizontal RecyclerView in a vertical RecyclerView in a horizontal ViewPager2).*/
class NestedScrollableHost : FrameLayout {constructor(context: Context) : super(context)constructor(context: Context, attrs: AttributeSet?) : super(context, attrs)private var touchSlop = 0private var initialX = 0fprivate var initialY = 0fprivate val parentViewPager: ViewPager2?get() {var v: View? = parent as? Viewwhile (v != null && v !is ViewPager2) {v = v.parent as? View}return v as? ViewPager2}private val child: View? get() = if (childCount > 0) getChildAt(0) else nullinit {touchSlop = ViewConfiguration.get(context).scaledTouchSlop}private fun canChildScroll(orientation: Int, delta: Float): Boolean {val direction = -delta.sign.toInt()return when (orientation) {0 -> child?.canScrollHorizontally(direction) ?: false1 -> child?.canScrollVertically(direction) ?: falseelse -> throw IllegalArgumentException()}}override fun onInterceptTouchEvent(e: MotionEvent): Boolean {handleInterceptTouchEvent(e)return super.onInterceptTouchEvent(e)}private fun handleInterceptTouchEvent(e: MotionEvent) {val orientation = parentViewPager?.orientation ?: return// Early return if child can't scroll in same direction as parentif (!canChildScroll(orientation, -1f) && !canChildScroll(orientation, 1f)) {return}if (e.action == MotionEvent.ACTION_DOWN) {initialX = e.xinitialY = e.yparent.requestDisallowInterceptTouchEvent(true)} else if (e.action == MotionEvent.ACTION_MOVE) {val dx = e.x - initialXval dy = e.y - initialYval isVpHorizontal = orientation == ORIENTATION_HORIZONTAL// assuming ViewPager2 touch-slop is 2x touch-slop of childval scaledDx = dx.absoluteValue * if (isVpHorizontal) .5f else 1fval scaledDy = dy.absoluteValue * if (isVpHorizontal) 1f else .5fif (scaledDx > touchSlop || scaledDy > touchSlop) {if (isVpHorizontal == (scaledDy > scaledDx)) {// Gesture is perpendicular, allow all parents to interceptparent.requestDisallowInterceptTouchEvent(false)} else {// Gesture is parallel, query child if movement in that direction is possibleif (canChildScroll(orientation, if (isVpHorizontal) dx else dy)) {// Child can scroll, disallow all parents to interceptparent.requestDisallowInterceptTouchEvent(true)} else {// Child cannot scroll, allow all parents to interceptparent.requestDisallowInterceptTouchEvent(false)}}}}}
}