xml布局如下：
<androidx.viewpager2.integration.testapp.NestedScrollableHost
? ? ? ? android:layout_width="match_parent"
? ? ? ? android:layout_height="wrap_content"
? ? ? ? android:layout_marginTop="8dp">
<androidx.viewpager2.widget.ViewPager2
android:id="@+id/viewPager2"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
? ? </androidx.viewpager2.integration.testapp.NestedScrollableHost>
自定義View：? NestedScrollableHost
/*
* 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.testapp
import 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 = 0
? ? private var initialX = 0f
? ? private var initialY = 0f
? ? private val parentViewPager: ViewPager2?
? ? ? ? get() {
? ? ? ? ? ? var v: View? = parent as? View
? ? ? ? ? ? while (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 null
? ? init {
? ? ? ? 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) ?: false
? ? ? ? ? ? 1 -> child?.canScrollVertically(direction) ?: false
? ? ? ? ? ? else -> 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 parent
? ? ? ? if (!canChildScroll(orientation, -1f) && !canChildScroll(orientation, 1f)) {
? ? ? ? ? ? return
? ? ? ? }
? ? ? ? if (e.action == MotionEvent.ACTION_DOWN) {
? ? ? ? ? ? initialX = e.x
? ? ? ? ? ? initialY = e.y
? ? ? ? ? ? parent.requestDisallowInterceptTouchEvent(true)
? ? ? ? } else if (e.action == MotionEvent.ACTION_MOVE) {
? ? ? ? ? ? val dx = e.x - initialX
? ? ? ? ? ? val dy = e.y - initialY
? ? ? ? ? ? val isVpHorizontal = orientation == ORIENTATION_HORIZONTAL
? ? ? ? ? ? // assuming ViewPager2 touch-slop is 2x touch-slop of child
? ? ? ? ? ? val scaledDx = dx.absoluteValue * if (isVpHorizontal) .5f else 1f
? ? ? ? ? ? val scaledDy = dy.absoluteValue * if (isVpHorizontal) 1f else .5f
? ? ? ? ? ? if (scaledDx > touchSlop || scaledDy > touchSlop) {
? ? ? ? ? ? ? ? if (isVpHorizontal == (scaledDy > scaledDx)) {
? ? ? ? ? ? ? ? ? ? // Gesture is perpendicular, allow all parents to intercept
? ? ? ? ? ? ? ? ? ? parent.requestDisallowInterceptTouchEvent(false)
? ? ? ? ? ? ? ? } else {
? ? ? ? ? ? ? ? ? ? // Gesture is parallel, query child if movement in that direction is possible
? ? ? ? ? ? ? ? ? ? if (canChildScroll(orientation, if (isVpHorizontal) dx else dy)) {
? ? ? ? ? ? ? ? ? ? ? ? // Child can scroll, disallow all parents to intercept
? ? ? ? ? ? ? ? ? ? ? ? parent.requestDisallowInterceptTouchEvent(true)
? ? ? ? ? ? ? ? ? ? } else {
? ? ? ? ? ? ? ? ? ? ? ? // Child cannot scroll, allow all parents to intercept
? ? ? ? ? ? ? ? ? ? ? ? parent.requestDisallowInterceptTouchEvent(false)
? ? ? ? ? ? ? ? ? ? }
? ? ? ? ? ? ? ? }
? ? ? ? ? ? }
? ? ? ? }
? ? }
}
其他滑動事件處理可以子ViewPager2 在外層包裹
<androidx.core.widget.NestedScrollView
? ? ? ? android:id="@+id/nestedScrollView"
? ? ? ? android:layout_width="match_parent"
? ? ? ? android:layout_height="match_parent">
? ? <androidx.viewpager2.integration.testapp.NestedScrollableHost
? ? ? ? android:layout_width="match_parent"
? ? ? ? android:layout_height="wrap_content"
? ? ? ? >
? ? ? ? <androidx.viewpager2.widget.ViewPager2
? ? ? ? ? ? android:id="@+id/viewPager2"
? ? ? ? ? ? android:layout_width="match_parent"
? ? ? ? ? ? android:layout_height="wrap_content" />
? ? </androidx.viewpager2.integration.testapp.NestedScrollableHost>
? ? </androidx.core.widget.NestedScrollView>
