SAPUi5类型错误:I。函数调用不是函数

我正在实现一个文件上传程序,显示在一个对话框中。相关代码:

function onAddExcelData() {
    var that = this;
    if(this.fixedDialog === undefined) {
        this.fixedDialog = new sap.m.Dialog({
            title: "Choose CSV File for Upload",
            beginButton: new sap.m.Button({
                text: "Upload",
                press: function(oEvent) {
                    that.fixedDialog.close();
                }
            }),  
            content: [
                new sap.ui.unified.FileUploader("excelUploader")
            ],
            endButton: new sap.m.Button({
                text: "Cancel",
                press: function() {
                    that.fixedDialog.close();
                }
            })
        })
       this.getView().addDependent(this.fixedDialog);
       this.fixedDialog.attachBeforeClose(this.setDataToJsonFromExcel, this);
   }

   this.fixedDialog.open();
}

每当我想单击beginButton或endButton时,控制台就会显示错误

Uncaught TypeError: I.fFunction.call is not a function

我读过关于这个问题的文章,建议的解决方案总是在调用press函数之前定义一个新变量。但是即使我添加了那个变量,我仍然得到了错误。有人有进一步的想法吗?