如何在 RecyclerView Android 中向 ItemDecoration 添加点击监听器？

Question

I have tried to add a click listener to itemdecoration like below but still no luck. Please help.

recyclerview.addOnItemTouchListener( object : RecyclerView.OnItemTouchListener{
    override fun onTouchEvent(rv: RecyclerView?, e: MotionEvent?) {

    }

    override fun onInterceptTouchEvent(rv: RecyclerView?, e: MotionEvent?): Boolean {
        val view = rv!!.findChildViewUnder(e!!.x, e!!.y)
        if(view == null) return false
        when(view.id){
            R.id.list_item_section_text->{
                Log.d("Clicked","Header")
            }
        }
        return false
    }

    override fun onRequestDisallowInterceptTouchEvent(disallowIntercept: Boolean) {

    }

})

Answer 1

ItemDecoration will help you draw something between items, but the View you're drawing in is actually the RecyclerView itself (according to Layout inspector), via its Canvas . So you won't be able to add an basic onClickListener on that decorations.

According to your code, I guess you have an item decoration for each of your items header?

What I would do for this would be not to consider my header as an ItemDecoration but as an item (with different type) I would feed my RecyclerView with.

sealed class RecyclerViewItem
object MainItem : RecyclerViewItem()
object Header : RecyclerViewItem()

In your adapter (with items: RecyclerViewItem ) you override getItemViewType method using custom ids. Then in onBindViewHolder you can check the item view type and add your onClickListener on your view if it's a Header .

For more info, you can search for building RecyclerView with different item type .

Answer 2

You can customize a RecyclerView and check if touch event arrives to ItemDecorator or no:

class YourRecyclerView @JvmOverloads constructor(
    context: Context, attrs: AttributeSet? = null, defStyleAttr: Int = 0
) : RecyclerView(context, attrs, defStyleAttr) {

    private val clicksFlow: MutableSharedFlow<ClickEvent> = MutableSharedFlow(
        extraBufferCapacity = 1, onBufferOverflow = BufferOverflow.DROP_OLDEST
    )

    fun getClicksFlow() = clicksFlow as Flow<RecyclerClickEvent>

    @SuppressLint("ClickableViewAccessibility")
    override fun onTouchEvent(e: MotionEvent) : Boolean{
        if (e.action == MotionEvent.ACTION_DOWN) {
            for (i in 0 until itemDecorationCount) {
                val decor = getItemDecorationAt(i)
                if (decor is YourDecoration && decor.isOnTouched(this, e)) {
                    clicksFlow.tryEmit(ClickEvent(e.x, e.y))
                    return true
                }
            }
        }
        return super.onTouchEvent(e)
    }

    override fun onInterceptTouchEvent(e: MotionEvent): Boolean {
        if (e.action == MotionEvent.ACTION_DOWN) {
            for (i in 0 until itemDecorationCount) {
                val decor = getItemDecorationAt(i)
                if (decor is YourDecoration && decor.isOnTouched(this, e)) {
                    return true
                }
            }
        }
        return super.onInterceptTouchEvent(e)
    }
}

class YourDecoration(/*some stuff*/) : RecyclerView.ItemDecoration() {

    fun isOnTouched(parent: YourRecyclerView , e: MotionEvent): Boolean {
        val w = abs(scaleX * width)
        val h = abs(scaleY * height)
        val top = topMargin - height / 2F - parent.paddingTop
        return if (scaleX > 0) {
            val side = parent.measuredWidth - sideMargin
            e.y >= top && e.y <= (top + h) && side >= e.x && (side - w) <= e.x
        } else {
            val side = sideMargin
            e.y >= top && e.y <= (top + h) && side <= e.x && e.x <= (side + w)
        }
    }
}