Menambahkan jawaban lain di sini sebagai yang di atas tidak memenuhi kebutuhan saya sepenuhnya atau tidak bekerja dengan baik. Yang ini sebagian didasarkan pada ide-ide yang tersebar di sini.
Jadi apa yang dilakukan orang ini?
Skenario ke bawah melemparkan: Jika AppBarLayout runtuh, itu memungkinkan RecyclerView melemparkan sendiri tanpa melakukan apa pun. Jika tidak, itu akan merobohkan AppBarLayout dan mencegah RecyclerView dari melakukan hubungan asmara. Segera setelah itu diciutkan (sampai pada titik yang diminta oleh kecepatan yang diberikan) dan jika ada kecepatan yang tersisa, RecyclerView akan terlempar dengan kecepatan asli minus apa yang dikonsumsi oleh AppBarLayout yang baru saja runtuh.
Skenario ke atas melempar: Jika gulir offset RecyclerView tidak nol, itu akan terlempar dengan kecepatan asli. Segera setelah itu selesai dan jika masih ada kecepatan yang tersisa (yaitu RecyclerView digulir ke posisi 0), AppBarLayout akan diperluas ke titik bahwa kecepatan asli dikurangi permintaan yang baru dikonsumsi. Jika tidak, AppBarLayout akan diperluas hingga ke titik yang dituntut oleh kecepatan asli.
AFAIK, ini adalah perilaku yang berubah-ubah.
Ada banyak refleksi yang terlibat, dan itu cukup khusus. Namun tidak ada masalah yang ditemukan. Itu juga ditulis di Kotlin, tetapi memahaminya seharusnya tidak ada masalah. Anda dapat menggunakan plugin IntelliJ Kotlin untuk mengkompilasinya ke bytecode -> dan mendekompilasinya kembali ke Jawa. Untuk menggunakannya, letakkan dalam paket android.support.v7.widget dan tetapkan sebagai AppatorbayL's CoordinatorLayout.LayoutParams perilaku dalam kode (atau tambahkan konstruktor xml yang berlaku atau sesuatu)
/*
* Copyright 2017 Julian Ostarek
*
* 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 android.support.v7.widget
import android.support.design.widget.AppBarLayout
import android.support.design.widget.CoordinatorLayout
import android.support.v4.widget.ScrollerCompat
import android.view.View
import android.widget.OverScroller
class SmoothScrollBehavior(recyclerView: RecyclerView) : AppBarLayout.Behavior() {
// We're using this SplineOverScroller from deep inside the RecyclerView to calculate the fling distances
private val splineOverScroller: Any
private var isPositive = false
init {
val scrollerCompat = RecyclerView.ViewFlinger::class.java.getDeclaredField("mScroller").apply {
isAccessible = true
}.get(recyclerView.mViewFlinger)
val overScroller = ScrollerCompat::class.java.getDeclaredField("mScroller").apply {
isAccessible = true
}.get(scrollerCompat)
splineOverScroller = OverScroller::class.java.getDeclaredField("mScrollerY").apply {
isAccessible = true
}.get(overScroller)
}
override fun onNestedFling(coordinatorLayout: CoordinatorLayout?, child: AppBarLayout, target: View?, velocityX: Float, givenVelocity: Float, consumed: Boolean): Boolean {
// Making sure the velocity has the correct sign (seems to be an issue)
var velocityY: Float
if (isPositive != givenVelocity > 0) {
velocityY = givenVelocity * - 1
} else velocityY = givenVelocity
if (velocityY < 0) {
// Decrement the velocity to the maximum velocity if necessary (in a negative sense)
velocityY = Math.max(velocityY, - (target as RecyclerView).maxFlingVelocity.toFloat())
val currentOffset = (target as RecyclerView).computeVerticalScrollOffset()
if (currentOffset == 0) {
super.onNestedFling(coordinatorLayout, child, target, velocityX, velocityY, false)
return true
} else {
val distance = getFlingDistance(velocityY.toInt()).toFloat()
val remainingVelocity = - (distance - currentOffset) * (- velocityY / distance)
if (remainingVelocity < 0) {
(target as RecyclerView).addOnScrollListener(object : RecyclerView.OnScrollListener() {
override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
if (newState == RecyclerView.SCROLL_STATE_IDLE) {
recyclerView.post { recyclerView.removeOnScrollListener(this) }
if (recyclerView.computeVerticalScrollOffset() == 0) {
super@SmoothScrollBehavior.onNestedFling(coordinatorLayout, child, target, velocityX, remainingVelocity, false)
}
}
}
})
}
return false
}
}
// We're not getting here anyway, flings with positive velocity are handled in onNestedPreFling
return false
}
override fun onNestedPreFling(coordinatorLayout: CoordinatorLayout?, child: AppBarLayout, target: View?, velocityX: Float, givenVelocity: Float): Boolean {
// Making sure the velocity has the correct sign (seems to be an issue)
var velocityY: Float
if (isPositive != givenVelocity > 0) {
velocityY = givenVelocity * - 1
} else velocityY = givenVelocity
if (velocityY > 0) {
// Decrement to the maximum velocity if necessary
velocityY = Math.min(velocityY, (target as RecyclerView).maxFlingVelocity.toFloat())
val topBottomOffsetForScrollingSibling = AppBarLayout.Behavior::class.java.getDeclaredMethod("getTopBottomOffsetForScrollingSibling").apply {
isAccessible = true
}.invoke(this) as Int
val isCollapsed = topBottomOffsetForScrollingSibling == - child.totalScrollRange
// The AppBarlayout is collapsed, we'll let the RecyclerView handle the fling on its own
if (isCollapsed)
return false
// The AppbarLayout is not collapsed, we'll calculate the remaining velocity, trigger the appbar to collapse and fling the RecyclerView manually (if necessary) as soon as that is done
val distance = getFlingDistance(velocityY.toInt())
val remainingVelocity = (distance - (child.totalScrollRange + topBottomOffsetForScrollingSibling)) * (velocityY / distance)
if (remainingVelocity > 0) {
(child as AppBarLayout).addOnOffsetChangedListener(object : AppBarLayout.OnOffsetChangedListener {
override fun onOffsetChanged(appBarLayout: AppBarLayout, verticalOffset: Int) {
// The AppBarLayout is now collapsed
if (verticalOffset == - appBarLayout.totalScrollRange) {
(target as RecyclerView).mViewFlinger.fling(velocityX.toInt(), remainingVelocity.toInt())
appBarLayout.post { appBarLayout.removeOnOffsetChangedListener(this) }
}
}
})
}
// Trigger the expansion of the AppBarLayout
super.onNestedFling(coordinatorLayout, child, target, velocityX, velocityY, false)
// We don't let the RecyclerView fling already
return true
} else return super.onNestedPreFling(coordinatorLayout, child, target, velocityX, velocityY)
}
override fun onNestedPreScroll(coordinatorLayout: CoordinatorLayout?, child: AppBarLayout?, target: View?, dx: Int, dy: Int, consumed: IntArray?) {
super.onNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed)
isPositive = dy > 0
}
private fun getFlingDistance(velocity: Int): Double {
return splineOverScroller::class.java.getDeclaredMethod("getSplineFlingDistance", Int::class.javaPrimitiveType).apply {
isAccessible = true
}.invoke(splineOverScroller, velocity) as Double
}
}
