private var isUserScrolling = false
private var hasScrolledUp = false // 是否向上滚动
private var lastScrollOffset = 0 // 上次滚动位置
private var isScrollingDown = false // 是否向下滚动
private var totalScrollDownDistance = 0 // 累计向下滚动距离

recyclerView.apply {
    this.layoutManager = layoutManager
    this.adapter = adapter

    itemAnimator = null

    // 添加滚动监听，检测用户手动滚动
    addOnScrollListener(object : RecyclerView.OnScrollListener() {
        override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
            super.onScrollStateChanged(recyclerView, newState)
            Log.d(TAG, "onScrollStateChanged: newState=$newState")
            isUserScrolling = newState != RecyclerView.SCROLL_STATE_IDLE
        }

        override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
            super.onScrolled(recyclerView, dx, dy)
            handleScrollChanged(dy)
        }
    })
}

scrollToEndBtn.setOnClickListener {
    val itemCount = adapter.itemCount
    if (itemCount > 0) {
        recyclerView.smoothScrollToPosition(itemCount - 1)
    }
}

/**
 * 处理滚动变化
 */
private fun handleScrollChanged(dy: Int) {
    val currentScrollOffset = recyclerView.computeVerticalScrollOffset()

    // 检测滚动方向
    if (dy > 0) {
        // 向下滚动 (正值表示向下)
        isScrollingDown = true
        totalScrollDownDistance += dy
    } else if (dy < 0) {
        // 向上滚动 (负值表示向上)
        isScrollingDown = false
        // 重置累计向下滚动距离
        totalScrollDownDistance = 0
    }

    // 检查最后2条Item是否可见
    val itemCount = adapter.itemCount
    val lastVisiblePosition = layoutManager.findLastVisibleItemPosition()
    val isNearBottom = itemCount > 2 && lastVisiblePosition >= itemCount - 2

    // 当向下滚动累计超过200时显示按钮，但如果最后2条Item可见则隐藏
    val shouldShow = isScrollingDown && totalScrollDownDistance > 200 && !isNearBottom

    if (shouldShow != hasScrolledUp) {
        hasScrolledUp = shouldShow
        scrollToEndBtn.isVisible = shouldShow
    }

    lastScrollOffset = currentScrollOffset
}

/**
 * 当页面底部不可见高度大于600像素，出现该btn
 */
private fun handleScrollChanged() {
    // 检查底部不可见内容高度
    val scrollRange = recyclerView.computeVerticalScrollRange()     // 总内容高度
    val scrollExtent = recyclerView.computeVerticalScrollExtent()   // 可见区域高度
    val scrollOffset = recyclerView.computeVerticalScrollOffset()   // 当前滚动位置
    val bottomInvisibleHeight = scrollRange - scrollExtent - scrollOffset // 底部不可见高度
    val shouldShow = bottomInvisibleHeight >= 600             // 是否接近底部

    if (shouldShow != hasScrolledUp) {
        hasScrolledUp = shouldShow
        scrollToEndBtn.isVisible = shouldShow
    }
}

import android.content.Context
import android.graphics.Canvas
import android.graphics.Paint
import android.graphics.drawable.Drawable
import android.text.style.ImageSpan

open class MarginImageSpan(
    context: Context,
    drawableRes: Int,
    val l: Int = 0,
    val r: Int = 0
) : ImageSpan(context, drawableRes) {

    override fun getSize(
        paint: Paint,
        text: CharSequence?,
        start: Int,
        end: Int,
        fm: Paint.FontMetricsInt?
    ): Int {
        val d: Drawable = drawable
        val rect = d.bounds

        if (fm != null) {
            val var7 = Paint.FontMetricsInt()
            paint.getFontMetricsInt(var7)
            fm.ascent = var7.ascent
            fm.descent = var7.descent
            fm.top = var7.top
            fm.bottom = var7.bottom
        }

        return l + rect.right + r
    }

    override fun draw(
        canvas: Canvas,
        text: CharSequence,
        start: Int,
        end: Int,
        x: Float,
        top: Int,
        y: Int,
        bottom: Int,
        paint: Paint
    ) {
        // image to draw
        val b = drawable
        // font metrics of text to be replaced
        val fm = paint.fontMetricsInt
        var transY = ((y + fm.descent + y + fm.ascent) / 2 - b.bounds.bottom / 2)
        // to check the last line.(当 image 在单独一行显示时可能会存在这个问题）
        if (transY > bottom - b.bounds.bottom) transY = bottom - b.bounds.bottom
        //
        val transX = x + l
        canvas.save()
        canvas.translate(transX, transY.toFloat())
        b.draw(canvas)
        canvas.restore()
    }
}

val spanStr = SpannableStringBuilder("#")
spanStr.append(data.seriesName)
val imageSpan = MarginImageSpan(context, R.drawable.home_ic, 0, 3.dp)
// 创建 ImageSpan
spanStr.setSpan(imageSpan, 0, 1, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE)