我无法将kendo下拉列表设置为只读

<input id="dropdownlist" />

$("#dropdownlist").kendoDropDownList({
    dataTextField: "text",
    dataValueField: "value",
    dataSource: [
        { text: "Option 1", value: "1" },
        { text: "Option 2", value: "2" },
        { text: "Option 3", value: "3" }
    ],
    readonly: true
});

$("#dropdownlist").kendoDropDownList({
    dataTextField: "text",
    dataValueField: "value",
    dataSource: [
        { text: "Option 1", value: "1" },
        { text: "Option 2", value: "2" },
        { text: "Option 3", value: "3" }
    ]
});

$("#dropdownlist").data("kendoDropDownList").enable(false);