使用jQueryUI日期选择器时无法更改输入背景颜色

<input type="text" id="datepicker" class="custom-input" />

.custom-input {
  background-color: #f1f1f1; /* 设置背景颜色为灰色 */
}

$(function() {
  $("#datepicker").datepicker({
    showButtonPanel: true,
    dateFormat: "yy-mm-dd",
    changeMonth: true,
    changeYear: true,
    yearRange: "1900:2100",
    showAnim: "slideDown",
    showOtherMonths: true,
    selectOtherMonths: true,
    showWeek: true,
    firstDay: 1,
    beforeShow: function(input, inst) {
      $(input).addClass("custom-input"); // 添加自定义的class
    }
  });
});