Android仿今日头条图片滑动退出效果-Kotlin版

1. 在下滑时，随着手指的移动，图片区域跟随移动，并且activity的背景和页码逐渐变的透明
2. 滑动距离不超过设定的临界值时，会有回弹效果。
3. 滑动超过设置的临界值时，放开手指，页面滑动退出消失
4. 图片可以正常放大缩小，页面不跟随手指上下滑动
5. 使用了共享元素的页面切换效果

上代码

class SlideCloseLayout(context: Context, attrs: AttributeSet? = null) : FrameLayout(context, attrs) {private var previousX: Float = 0fprivate var previousY: Float = 0fprivate var scrollListener: LayoutScrollListener? = nullinit {background?.alpha = 255}override fun onInterceptTouchEvent(ev: MotionEvent?): Boolean {ev?.pointerCount?.let {if (it > 1) return falseval y: Float = ev.rawYval x: Float = ev.rawXwhen (ev.action) {MotionEvent.ACTION_DOWN -> {previousX = xpreviousY = y}MotionEvent.ACTION_MOVE -> {val diffY = y - previousYval diffX = x - previousXif (diffY <= 0) return falseif (Math.abs(diffX) + 50 < Math.abs(diffY)) {return true}}}}return false}override fun onTouchEvent(ev: MotionEvent?): Boolean {ev?.let {val y = ev.rawYval x = ev.rawXwhen (ev.action) {MotionEvent.ACTION_DOWN -> {previousX = xpreviousY = y}MotionEvent.ACTION_MOVE -> {val d