recycleview 滑动辅助

import android.content.Context
import android.graphics.Rect
import android.util.DisplayMetrics
import android.util.Log
import android.view.View
import androidx.recyclerview.widget.GridLayoutManager
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.LinearSmoothScroller
import androidx.recyclerview.widget.RecyclerView
import kotlinx.coroutines.delay
import java.lang.ref.SoftReference
import kotlin.math.abs
import kotlin.math.min
import kotlin.math.sqrt

/**

• https://www.jianshu.com/p/9ec5098655b7

• 自动播放的工具
  */
  class AutoPlayTool {
  val tag = "AutoPlayTool"

  //辅助接口
  public interface ISelectItemListener {
  /**
  * 参数1与参数2相等则是同一个，无需处理
  * 参数1与参数2不相等，应该停止掉参数2，播放参数1
  */
  fun onItem(new: Int, old: Int)
  }

  private var softSelectItemListener: SoftReference? = null
  private var visiblePercent = 1

  /**
  *热点区域，最接近这个位置的则锚定
  */
  var anchorPoint = 0

  constructor(visiblePercent: Int = 1) {
  this.visiblePercent = visiblePercent
  }

  /**

  • 当滑动停止的时候，开始视频播放
  • @param recyclerView
  • @return
    */
    @Deprecated("")
    fun onActiveWhenNoScrolling(recyclerView: RecyclerView, y: Int): Int {
    val index = calculateIndex(recyclerView, y)
    smoothScrollToPosition(calculateIndex(recyclerView, y))
    return index
    }

  /**

  • 获取可见百分比
  • @param v
  • @return
    */
    private fun getVisiblePercent(v: View): Int {
    val r = Rect()
    val visible = v.getLocalVisibleRect(r)
    if (visible && v.measuredHeight > 0) {
    val percent = 100 * r.height() / v.measuredHeight
    return percent
    }
    return -1
    }

  private fun getVisible(v: View, value: Int): Boolean {
  val r = Rect()
  val visible = v.getLocalVisibleRect(r)
  if (visible && v.visibility == View.VISIBLE) {
  return if (getVisiblePercent(v) >= value) {
  true
  } else {
  false
  }
  }
  return false
  }

  var ss: RecyclerView.OnScrollListener = object : RecyclerView.OnScrollListener() {
  var maxY: Int = 0
  var talY: Int = 0

  override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
  super.onScrollStateChanged(recyclerView, newState)
  if (newState == RecyclerView.SCROLL_STATE_IDLE) {
  recyclerView.removeOnScrollListener(this)
  smoothScrollToPosition(calculateIndex(recyclerView, talY))
  // onActiveWhenNoScrolling(recyclerView, talY)
  maxY = 0
  talY = 0
  }
  }

  override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
  super.onScrolled(recyclerView, dx, dy)
  Log.d("定位", "onScrolled Y=\(dy") if (abs(dy.toDouble()) > abs(maxY.toDouble())) { maxY = dy } talY += dy } } var lastPlay = -1 fun smoothScrollToPosition(position: Int, finish: (() -> Unit)? = null) { val viewLocation = IntArray(2) withRecyclerView.getLocationOnScreen(viewLocation) Log.d(tag, "锚定位置\){anchorPoint} 当前RecycleView Y=" + viewLocation[1])
  withRecyclerView.smoothScrollToPositionWithOffset(position, anchorPoint - viewLocation[1]) {
  softSelectItemListener?.get()?.onItem(position, lastPlay)
  Log.d(tag, "新位置\(position 旧位置\)lastPlay")
  lastPlay = position
  finish?.invoke()
  }
  }

  fun smoothScrollToPosition1(position: Int, finish: (() -> Unit)? = null) {
  val viewLocation = IntArray(2)
  withRecyclerView.getLocationOnScreen(viewLocation)
  Log.d(tag, "锚定位置\({anchorPoint} 当前RecycleView Y=" + viewLocation[1]) withRecyclerView.smoothScrollToPositionWithOffset1( position, anchorPoint - viewLocation[1] ) { softSelectItemListener?.get()?.onItem(position, lastPlay) Log.d(tag, "新位置\)position 旧位置$lastPlay")
  lastPlay = position
  finish?.invoke()
  }
  }

  private lateinit var withRecyclerView: RecyclerView
  fun attachToRecyclerView(recyclerView: RecyclerView) {
  withRecyclerView = recyclerView
  //增加一层代理，防止移动过程中造成的自动触发跳屏
  recyclerView.addOnScrollListener(object : RecyclerView.OnScrollListener() {
  override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
  super.onScrollStateChanged(recyclerView, newState)
  if (newState == RecyclerView.SCROLL_STATE_DRAGGING) {
  recyclerView.removeOnScrollListener(ss)
  recyclerView.addOnScrollListener(ss)
  }
  }
  })
  }

  fun withToRecyclerView(recyclerView: RecyclerView) {
  withRecyclerView = recyclerView
  }

  /**

  • 计算位置，滑动方向影响计算方式
  • @param recyclerView
  • @param direction 0表示未滑动，1表示向上滑（内容底部到顶部），-1表示下拉（内容从顶部到底部）
  • @return
    */
    fun calculateIndex(recyclerView: RecyclerView, direction: Int = 0): Int {
    var layoutManager: LinearLayoutManager? = null
    var position = -1
    if (recyclerView.layoutManager is LinearLayoutManager) {
    layoutManager = recyclerView.layoutManager as LinearLayoutManager?
    }
    val viewLocation = IntArray(2)
    recyclerView.getLocationOnScreen(viewLocation)
    Log.d(tag, "RecycleView Y=" + viewLocation[1])
    if (layoutManager != null) {
    var firstItemPosition = layoutManager.findFirstVisibleItemPosition()
    val lastItemPosition = layoutManager.findLastVisibleItemPosition()
    val items: LinkedHashMap<Int, RecyclerView.ViewHolder> = LinkedHashMap()
    while (firstItemPosition <= lastItemPosition) {
    val holder = recyclerView.findViewHolderForLayoutPosition(firstItemPosition)
    val view = holder?.itemView
    if (view != null && getVisible(view, visiblePercent)) {
    items[firstItemPosition] = holder
    }
    firstItemPosition++
    }
    //最小距离
    var minDistance = Int.MAX_VALUE
    //找出距离中间最近的一个
    for ((key, value) in items) {
    val itemDistance = calculatedDistance(value.itemView, direction = direction)
    if (itemDistance < minDistance) {
    minDistance = itemDistance
    position = key
    }
    }
    }
    return position
    }

  /**

  • 计算视图距离屏幕中心的距离。

  • 该方法通过获取视图在屏幕上的位置，然后计算该位置与屏幕中心垂直距离的绝对值。

  • 这样做的目的是为了评估视图与屏幕中心的相对位置，用于某些基于位置的布局或交互逻辑。

  • @param view 要计算距离的视图对象。

  • @param point 屏幕目标绝对位置。

  • @param direction 0表示未滑动，1表示向上滑（内容底部到顶部），-1表示下拉（内容从顶部到底部）

  • @return 视图距离屏幕中心的垂直距离的绝对值。
    */
    private fun calculatedDistance(view: View, point: Int = anchorPoint, direction: Int = 0): Int {
    val viewLocation = IntArray(2)
    view.getLocationOnScreen(viewLocation)
    //检测用户意图偏移量
    val tagPoint = when (direction) {
    in 1..Int.MAX_VALUE -> { //上滑动
    point + (view.height * 0.8).toInt()
    }

    in Int.MIN_VALUE..(-1) -> {//拉下滑动
    // 处理小于等于-1的情况
    point - (view.height * 0.8).toInt()
    }

    else -> {
    point
    }
    }
    return abs((viewLocation[1] - tagPoint).toDouble()).toInt()
    }

}

private fun RecyclerView.smoothScrollToPositionWithOffset(
position: Int,
offset: Int,
finish: (() -> Unit)? = null
) {
val linearSmoothScroller = object : LinearSmoothScroller(context) {
override fun onTargetFound(
targetView: View,
state: RecyclerView.State,
action: Action
) {
super.onTargetFound(targetView, state, action)
val dx = calculateDxToMakeVisible(targetView, horizontalSnapPreference)
val dy = calculateDyToMakeVisible(targetView, SNAP_TO_START)

val distance = sqrt((dx * dx + dy * dy).toDouble()).toInt()
val time = calculateTimeForDeceleration(distance)
if (time > 0) {
action.update(-dx, -dy - offset, time, mDecelerateInterpolator)
}
}

override fun onStop() {
super.onStop()
finish?.invoke()
}
}
linearSmoothScroller.targetPosition = position
layoutManager?.startSmoothScroll(linearSmoothScroller)
}

private fun RecyclerView.smoothScrollToPositionWithOffset1(
position: Int,
offset: Int,
finish: (() -> Unit)? = null
) {
(layoutManager as? LinearLayoutManager)?.scrollToPositionWithOffset(position, offset)
post { finish?.invoke() }

}

/**

• 寻找完全可见的item
• @param last 是否是最后一个
• @return 下标
  */
  fun RecyclerView.findCompletelyVisibleItemPosition(last: Boolean = false): Int {
  var completelyVisibleItemPosition = -1
  // 滑动结束，获取第一个完全可见的 item
  val layoutManager = layoutManager
  if (layoutManager is LinearLayoutManager) {
  // 对于 LinearLayoutManager
  completelyVisibleItemPosition =
  if (last) layoutManager.findLastCompletelyVisibleItemPosition() else layoutManager.findFirstCompletelyVisibleItemPosition()
  } else if (layoutManager is GridLayoutManager) {
  completelyVisibleItemPosition =
  if (last) layoutManager.findLastCompletelyVisibleItemPosition() else layoutManager.findFirstCompletelyVisibleItemPosition()
  }
  return completelyVisibleItemPosition
  }

/**

• 获取可见百分比
• @param v
• @return
  */
  fun View.getVisiblePercent(): Int {
  val r = Rect()
  val visible = getLocalVisibleRect(r)
  if (visible && measuredHeight > 0) {
  val percent = 100 * r.height() / measuredHeight
  return percent
  }
  return 0
  }