由于 Window 的 decorView 默认是设置有 10dp 的padding。需要获取到decorView后设置其padding为(0, 0, 0, 0) 即可。

override fun onStart() {
        Logger.i(TAG, "onStart")
        super.onStart()
        setWindowParam()
    }

    /**
     * 设置dialog的 window 参数
     */
    private fun setWindowParam() {
        val win = dialog?.window
        win?.setBackgroundDrawable(ColorDrawable(Color.TRANSPARENT))
        activity?.windowManager?.defaultDisplay?.getMetrics(DisplayMetrics())
        win?.decorView?.setPadding(0, 0, 0, 0)

        val params = win?.attributes ?: WindowManager.LayoutParams()
        params?.dimAmount = 0f
        params?.gravity = Gravity.BOTTOM
        params?.width = MATCH_PARENT
        params?.height = MATCH_PARENT
        win?.attributes = params
    }