代码分享：实现自动滚动和无限滚动以及一些细致的交互

代码分享

分享点Android基础代码吧~

本想找个轮子，轮子没找到，只能自己搞了。
话不多说，直接上代码干货，分享给后面有需要的xdm，直接拿去用。
整体实现不算复杂，就费点时间，已抽离不相干的代码。

实现效果

1. 无限循环顺滑滚动
2. 触摸停止滚动，抬手n秒后继续滚动
3. 实时记录当前可见的视图
4. 支持由后台控制滚动频率
5. 支持动态插拔
6. 数据更新动画

涉及到的Android知识点包括

1. 自定义View
2. RecyclerView
3. Glide
4. 动画
5. 定时器
6. 事件分发机制
7. handle机制
8. 另外：编程语言是kotlin
9. 注意：这里使用到的动画以及Handler需要做好及时取消与清除，避免内存泄漏问题。

核心代码：

1. 实现无限：

private var itemCount = Int.MAX_VALUE
override fun getItemCount(): Int {
    
    
    return if (list.size > 4) itemCount else list.size
}

2. 实现顺滑滚动：

this@AutoScrollRecyclerView.scrollBy(scrollDistance,0)

3. 实现触摸启停滚动：

override fun dispatchTouchEvent(ev: MotionEvent?): Boolean {
    
    
    val action = ev?.action
    if (action == MotionEvent.ACTION_UP || action == MotionEvent.ACTION_CANCEL || action == MotionEvent.ACTION_OUTSIDE) {
    
    
        handleTimeHandler(true)
    } else if (action == MotionEvent.ACTION_DOWN) {
    
    
        handleTimeHandler(false)
    }
    return super.dispatchTouchEvent(ev)
}
fun handleTimeHandler(isOpen: Boolean){
    
    
    isOpenTimeHandler = isOpen
    mTimeHandler.removeMessages(0)
    if(isOpenTimeHandler){
    
    
        mTimeHandler.sendEmptyMessageDelayed(0,2000)
    }else {
    
    
        //([email protected] as SpecialScrollChildAdapter).isAutoScroll(false)
    }

}

4. 统计当前展示的item：

it.addOnScrollListener(object : RecyclerView.OnScrollListener() {
    
    
    override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
    
    
        (it.layoutManager as LinearLayoutManager).findFirstCompletelyVisibleItemPosition().let {
    
    
            //业务逻辑代码...
        }
    }
})

5. 动画

ValueAnimator.ofFloat(0f, 1f).apply {
    
    
		duration = animationDuration
		addUpdateListener {
    
     animation ->
			val alpha = animation.animatedValue as Float
			view.alpha = alpha
		}
		start()
	}

自定义RecyclerView

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

	private var isOpenTimeHandler: Boolean = true

	val time: Long = 20// 缩短滚动间隔
	val scrollDistance: Int = 10 //单次滚动距离
	//这里也可选择直接使用TimerTask
	private val mTimeHandler : Handler by lazy {
		object : Handler(Looper.getMainLooper()){
			override fun handleMessage(msg: Message) {
				super.handleMessage(msg)
				[email protected](scrollDistance,0)
				if (isOpenTimeHandler) { // 如果允许滚动，则继续发送消息
					//([email protected] as SpecialScrollChildAdapter).isAutoScroll(true)
					mTimeHandler.sendEmptyMessageDelayed(0, time)
				}
			}
		}
	}

	//处理触摸停止滚动逻辑
	override fun dispatchTouchEvent(ev: MotionEvent?): Boolean {
		val action = ev?.action
		if (action == MotionEvent.ACTION_UP || action == MotionEvent.ACTION_CANCEL || action == MotionEvent.ACTION_OUTSIDE) {
			handleTimeHandler(true)
		} else if (action == MotionEvent.ACTION_DOWN) {
			handleTimeHandler(false)
		}
		return super.dispatchTouchEvent(ev)
	}

    override fun onInterceptTouchEvent(e: MotionEvent): Boolean {
        return super.onInterceptTouchEvent(e)
    }

    override fun onTouchEvent(e: MotionEvent): Boolean {
        return super.onTouchEvent(e)
    }

	fun handleTimeHandler(isOpen: Boolean){
		isOpenTimeHandler = isOpen
		mTimeHandler.removeMessages(0)
		if(isOpenTimeHandler){
			mTimeHandler.sendEmptyMessageDelayed(0,2000)
		}else {
			//([email protected] as SpecialScrollChildAdapter).isAutoScroll(false)
		}

	}

}

Adapter

class SpecialScrollChildAdapter(private val context: Context, private var list: List<Any>) :
    RecyclerView.Adapter<SpecialScrollChildAdapter.ViewHolder>() {

    private var itemCount = Int.MAX_VALUE

    fun isAutoScroll(isAutoScroll: Boolean) {
        itemCount = if (isAutoScroll) Int.MAX_VALUE else list.size
        notifyDataSetChanged()
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        val view = LayoutInflater.from(context).inflate(R.layout.item_new_home_session_scroll_child, parent, false)

        return ViewHolder(view)
    }

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
		holder.initData(this.list[position % this.list.size])
    }

    override fun getItemCount(): Int {
        return if (list.size > 4) itemCount else list.size
    }


    class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        fun initData(any: Any) {
			itemView.findViewById<ImageView>(R.id.iv_session_scroll_good_img)?.load("url")
			itemView.findViewById<TextView>(R.id.tv_session_scroll_good_price)?.text = "测试：" + any.toString()
        }
    }
}

使用

rv_auto_scroll.let{
    it.layoutManager = LinearLayoutManager(view!!.context, LinearLayoutManager.HORIZONTAL, false)
    it.adapter = SpecialScrollChildAdapter(view.context, mutableListOf<Any>())
    if (it.itemDecorationCount > 0) {
        it.removeItemDecorationAt(0)
    }

    it.addItemDecoration {
        width = 15.dp
        linear {
            drawTop = false
            drawBottom = false
            drawLeft = false
            drawRight = false
        }

    }
    it.postDelayed({
        it.handleTimeHandler(true)
    }, 200)

    it.addOnScrollListener(object : RecyclerView.OnScrollListener() {
        override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
            (it.layoutManager as LinearLayoutManager).findFirstCompletelyVisibleItemPosition().let {
            }
        }
    })
}