Android WebView如何判断是否滚动到底部

 x5WebView?.let {
    it.webViewClient = object : WebViewClient() {
	    override fun onPageFinished(
	           view: WebView,
	           url: String
	       ) {
	           super.onPageFinished(view, url)
	           postSafeDelayed(1000) {
	               loading_pb.visibility = View.GONE
	           }
	           //页面加载完判断是否到底部逻辑
	           view.post {
	                view.measure(0, 0)
	                val htmlContentHeight: Int = view.getMeasuredHeight()
	                val viewHeight: Int = view.getHeight()
	                //如果html高度小于控件高度，那么说明一屏可以展示下直接显示关闭按钮
	                if(htmlContentHeight <= viewHeight){
	                	// TODO 显示关闭按钮
	                }else{
	                //这里说明有滚动条，就需要监听滚动事件
	                	view?.setOnCustomScrollChangedListener(object : WebView.CustomScrollChangeListener{
                        override fun onScrollChange(
                            scrollX: Int,
                            scrollY: Int,
                            oldScrollX: Int,
                            oldScrollY: Int
                        ) {
                            Timber.w("setOnCustomScrollChangedListener 滚动底部，html高度:${htmlContentHeight},scrollY:${scrollY}")
                            //已经处于底端
                            if(htmlContentHeight - (viewHeight + scrollY) <= 0){
                                Timber.w("setOnCustomScrollChangedListener 到达底部")
                                //TODO 到达底部
                            }
                        }
                    })
	                }
                
				}
	       }
	   	}
  }
}