Android 触摸事件的分发

原理：

伪代码

override fun dispatchTouchEvent(ev: MotionEvent?): Boolean {
    var isConsume = false
    if (onInterceptTouchEvent(ev)) {
        isConsume = onTouchEvent(ev)
    } else {
        isConsume = child.dispatchTouchEvent(ev)
    }
    return isConsume
}

外部拦截法：

    private var lastX = 0F
    private var lastY = 0F

    override fun onInterceptTouchEvent(e: MotionEvent?): Boolean {
        var isIntercept = false
        var currentX = e!!.getX()
        var currentY = e!!.getY()
        when (e.action) {
            MotionEvent.ACTION_DOWN -> {
                isIntercept = false
            }
            MotionEvent.ACTION_MOVE -> {
                // 根据业务需求，自己实现
                isIntercept = abs(currentY - lastY) > abs(currentX - lastX)
            }
            MotionEvent.ACTION_UP -> {
                isIntercept = false
            }
        }
        lastX = currentX
        lastY = currentY
        return isIntercept
    }

内部拦截法：

    private var lastX = 0F
    private var lastY = 0F

    override fun dispatchTouchEvent(e: MotionEvent?): Boolean {
        var currentX = e!!.getX()
        var currentY = e!!.getY()
        when (e.action) {
            MotionEvent.ACTION_DOWN -> {
                parent.requestDisallowInterceptTouchEvent(true)
            }
            MotionEvent.ACTION_MOVE -> {
                // 根据业务需求，自己实现
                if (abs(currentY - lastY) > abs(currentX - lastX)) {
                    parent.requestDisallowInterceptTouchEvent(false)
                }
            }
            MotionEvent.ACTION_UP -> {
            }
        }
        lastX = currentX
        lastY = currentY
        return super.dispatchTouchEvent(e)
    }