Android RecyclerView 滑动删除，仅在第一个元素上绘制图标

Question

一切都运转良好，但有一件事并没有真正发挥作用。删除图标仅呈现在回收器视图列表的第一个元素上，如图所示。

这是我的 ItemTouchHelper 类的代码：

class ItemSwipeCallback(val context: Context) : ItemTouchHelper.Callback() {
    private val listeners = ArrayList<OnItemSwipe>()

    private val paint = Paint()
    val theme = context.themeId
    val icon = ContextCompat.getDrawable(context, R.drawable.ic_delete_filled_white_24dp)!!

    override fun onMove(
        recyclerView: RecyclerView,
        viewHolder: RecyclerView.ViewHolder,
        target: RecyclerView.ViewHolder): Boolean {

        return true
    }

    override fun getMovementFlags(recyclerView: RecyclerView, viewHolder: RecyclerView.ViewHolder): Int {
        val direction = context.sharedPreferences.getInt(Preferences.SWIPE_DIRECTION, Preferences.SWIPE_VALUE_RIGHT)

        return when (direction) {
            Preferences.SWIPE_VALUE_RIGHT -> makeMovementFlags(0, ItemTouchHelper.RIGHT)
            Preferences.SWIPE_VALUE_LEFT -> makeMovementFlags(0, ItemTouchHelper.LEFT)
            else -> makeMovementFlags(0, ItemTouchHelper.RIGHT)
        }
    }

    override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
        listeners.forEach { it.onSwiped(viewHolder.layoutPosition, direction) }
    }

    override fun onChildDraw(c: Canvas, recyclerView: RecyclerView, viewHolder: RecyclerView.ViewHolder,
            dX: Float, dY: Float, actionState: Int, isCurrentlyActive: Boolean) {

        super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive)

        if (dX != 0f && isCurrentlyActive) {
            val itemView = viewHolder.itemView
            paint.color = Color.parseColor("#D32F2F")
            val top = (itemView.height - icon.intrinsicHeight) / 2
            val left = itemView.width - icon.intrinsicWidth - top

            if (theme == Preferences.THEME_VALUE_DARK) {
                icon.setTint(Color.BLACK)
            } else {
                icon.setTint(Color.WHITE)
            }

            if (dX < 0) {
                val background = RectF(itemView.right.toFloat() + dX, itemView.top.toFloat(),
                    itemView.right.toFloat(), itemView.bottom.toFloat())
                c.drawRect(background, paint)
                icon.setBounds(left, top, left + icon.intrinsicWidth, top + icon.intrinsicHeight)
            } else {
                val background = RectF(itemView.left.toFloat() + dX, itemView.top.toFloat(),
                    itemView.left.toFloat(), itemView.bottom.toFloat())
                c.drawRect(background, paint)
                icon.setBounds(top, top, top + icon.intrinsicWidth, top + icon.intrinsicHeight)
            }
            icon.draw(c)
        }
    }

    fun addOnItemSwipeListener(onItemSwipe: OnItemSwipe) {
        listeners.add(onItemSwipe)
    }
}

也许加载在类头部的图标只能使用一次？我已经尝试将其转换为位图并使用它。我还尝试将其加载到 onChildDraw 函数中。

Answer 1

解决办法太简单了。我总是用itemView.height代替itemView.top.

画布包含所有项目。并非每个项目都有自己的画布。所以我也必须添加上述项目的高度。

工作代码如下所示：

val top = itemView.top + (itemView.height - intrinsicHeight) / 2
val left = itemView.width - intrinsicWidth - (itemView.height - intrinsicHeight) / 2
val right = left + intrinsicHeight
val bottom = top + intrinsicHeight

if (dX < 0) {
    background.setBounds(itemView.right + dX.toInt(), itemView.top, itemView.right, itemView.bottom)
    icon.setBounds(left, top, right, bottom)
} else if (dX > 0) {
    background.setBounds(itemView.left + dX.toInt(), itemView.top, itemView.left, itemView.bottom)
    icon.setBounds(top, top, top, bottom)
}
background.draw(c)
icon.draw(c)