大量文本的浏览进度和浏览时长统计
埋点需求，Android App 需要在onResume 和 onPause 方法中计算浏览的时长，同时上报浏览的进度。
浏览进度Rate具体的计算方式的具体过程：
1、在滚动屏幕过程中，通过 textContent?.viewTreeObserver?.addOnScrollChangedListener 来记录屏幕滚动的位置
2、在滚动监听里通过textContent?.getLocationOnScreen(location)获取在屏幕的具体位置，同时，
计算出visibleHeight = screenHeight - location[1] 当前文本的可见高度
3、当可见高度超过目标的高度，则认为已经全部浏览，rate = 100% ，同时移除滚动监听textContent?.viewTreeObserver?.removeOnScrollChangedListener(mScrollChangeListener)
核心代码如下：
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| private var totalHeight: Int = 0
private var visibleHeight: Int = 0
private var screenHeight = 0
fun getViewRate(): String? =
if (totalHeight <= 0 || visibleHeight < 0) null
else "${(visibleHeight * 100 / totalHeight)}%"
private fun bindViewTreeObserver() {
cleanCache()
contentTv.post {
totalHeight = contentTv.height
screenHeight = ScreenUtils.getScreenHeight(context)
contentVisibleRate()
}
contentTv.viewTreeObserver.addOnScrollChangedListener(mScrollChangeListener)
}
private fun cleanCache() {
totalHeight = 0
screenHeight = 0
visibleHeight = 0
}
private val mScrollChangeListener = ViewTreeObserver.OnScrollChangedListener {
contentVisibleRate()
}
private fun contentVisibleRate() {
val location = IntArray(2)
contentTv.getLocationOnScreen(location)
visibleHeight = (screenHeight - location[1]).coerceAtLeast(visibleHeight)
if (visibleHeight >= totalHeight) {
visibleHeight = totalHeight
removeOnScrollChangedListener()
}
}
private fun removeOnScrollChangedListener() {
mScrollChangeListener?.let {
contentTv.viewTreeObserver.removeOnScrollChangedListener(mScrollChangeListener)
}
}
|