如何向滑动按钮添加图像？ ItemTouchHelper示例

问题描述

我有一个示例SwipeHelper类，该类在RecyclerView菜单中创建一个滑动按钮。但是它仅在显示的按钮上显示文本，我想添加图像。有人可以告诉我如何在课堂上正确拼写出来吗。

SwipeHelper.kt

abstract class SwipeHelper(
    private val recyclerView: RecyclerView
) : itemtouchhelper.SimpleCallback(
    itemtouchhelper.ACTION_STATE_IDLE,itemtouchhelper.LEFT
) {
    private var swipedPosition = -1
    private val buttonsBuffer: MutableMap<Int,List<UnderlayButton>> = mutableMapOf()
    private val recoverQueue = object : LinkedList<Int>() {
        override fun add(element: Int): Boolean {
            if (contains(element)) return false
            return super.add(element)
        }
    }

    @SuppressLint("ClickableViewAccessibility")
    private val touchListener = View.OnTouchListener { _,event ->
        if (swipedPosition < 0) return@OnTouchListener false
        buttonsBuffer[swipedPosition]?.forEach { it.handle(event) }
        recoverQueue.add(swipedPosition)
        swipedPosition = -1
        recoverSwipedItem()
        true
    }

    init {
        recyclerView.setonTouchListener(touchListener)
    }

    private fun recoverSwipedItem() {
        while (!recoverQueue.isEmpty()) {
            val position = recoverQueue.poll() ?: return
            recyclerView.adapter?.notifyItemChanged(position)
        }
    }

    private fun drawButtons(
        canvas: Canvas,buttons: List<UnderlayButton>,itemView: View,dX: Float
    ) {
        var right = itemView.right
        buttons.forEach { button ->
            val width = button.intrinsicWidth / buttons.intrinsicWidth() * abs(dX)
            val left = right - width
            button.draw(
                canvas,RectF(left,itemView.top.toFloat(),right.toFloat(),itemView.bottom.toFloat())
            )

            right = left.toInt()
        }
    }

    override fun onChildDraw(
        c: Canvas,recyclerView: RecyclerView,viewHolder: RecyclerView.ViewHolder,dX: Float,dY: Float,actionState: Int,isCurrentlyActive: Boolean
    ) {
        val position = viewHolder.adapterPosition
        var maxDX = dX
        val itemView = viewHolder.itemView

        if (actionState == itemtouchhelper.ACTION_STATE_SWIPE) {
            if (dX < 0) {
                if (!buttonsBuffer.containsKey(position)) {
                    buttonsBuffer[position] = instantiateUnderlayButton(position)
                }

                val buttons = buttonsBuffer[position] ?: return
                if (buttons.isEmpty()) return
                maxDX = max(-buttons.intrinsicWidth(),dX)
                drawButtons(c,buttons,itemView,maxDX)
            }
        }

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

    override fun onMove(
        recyclerView: RecyclerView,target: RecyclerView.ViewHolder
    ): Boolean {
        return false
    }

    override fun onSwiped(viewHolder: RecyclerView.ViewHolder,direction: Int) {
        val position = viewHolder.adapterPosition
        if (swipedPosition != position) recoverQueue.add(swipedPosition)
        swipedPosition = position
        recoverSwipedItem()
    }

    abstract fun instantiateUnderlayButton(position: Int): List<UnderlayButton>

    //region UnderlayButton
    interface UnderlayButtonClickListener {
        fun onClick()
    }

    class UnderlayButton(
        private val context: Context,private val title: String,textSize: Float,@ColorRes private val colorRes: Int,private val clickListener: UnderlayButtonClickListener
    ) {
        private var clickableRegion: RectF? = null
        private val textSizeInPixel: Float = textSize * context.resources.displayMetrics.density // dp to px
        private val horizontalPadding = 50.0f
        val intrinsicWidth: Float

        init {
            val paint = Paint()
            paint.textSize = textSizeInPixel
            paint.typeface = Typeface.DEFAULT_BOLD
            paint.textAlign = Paint.Align.LEFT
            val titleBounds = Rect()
            paint.getTextBounds(title,title.length,titleBounds)
            intrinsicWidth = titleBounds.width() + 2 * horizontalPadding
        }

        fun draw(canvas: Canvas,rect: RectF) {
            val paint = Paint()

            // Draw background
            paint.color = ContextCompat.getColor(context,colorRes)
            canvas.drawRect(rect,paint)

            // Draw title
            paint.color = ContextCompat.getColor(context,android.R.color.white)
            paint.textSize = textSizeInPixel
            paint.typeface = Typeface.DEFAULT_BOLD
            paint.textAlign = Paint.Align.LEFT

            val titleBounds = Rect()
            paint.getTextBounds(title,titleBounds)

            val y = rect.height() / 2 + titleBounds.height() / 2 - titleBounds.bottom
            canvas.drawText(title,rect.left + horizontalPadding,rect.top + y,paint)

            clickableRegion = rect
        }

        fun handle(event: MotionEvent) {
            clickableRegion?.let {
                if (it.contains(event.x,event.y)) {
                    clickListener.onClick()
                }
            }
        }
    }
    //endregion
}

private fun List<SwipeHelper.UnderlayButton>.intrinsicWidth(): Float {
    if (isEmpty()) return 0.0f
    return map { it.intrinsicWidth }.reduce { acc,fl -> acc + fl }
}

这是我现在的滑动按钮的外观。 enter image description here

解决方法

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