lachang-wxapp/ThorUI/components/top-dropdown/top-dropdown.wxss

.tui-dropdown-box {
  width: 100%;
  position: fixed;
  box-sizing: border-box;
  border-bottom-right-radius: 24rpx;
  border-bottom-left-radius: 24rpx;
  transform: translateZ(0);
  overflow: hidden;
  visibility: hidden;
  transition: all 0.3s ease-in-out;
  z-index: 998;
  top:0;
}

.tui-dropdown-show {
  visibility: visible;
}

.tui-dropdown-mask {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(0, 0, 0, 0.6);
  z-index: 996;
  transition: all 0.3s ease-in-out;
  opacity: 0;
  visibility: hidden;
}

.tui-mask-show {
  opacity: 1;
  visibility: visible;
}