根据https链接点击按钮下载文件

        filePreview(row) {
            fetch(row.attachmentContent.url).then(res =>
                res.blob().then(blob => {
                    var a = document.createElement('a');
                    var url = window.URL.createObjectURL(blob);
                    var name = row.attachmentContent.name;
                    a.href = url;
                    a.download = name; // 下载名称
                    a.click();
                    window.URL.revokeObjectURL(url);
                })
            );
        },