重点：不要用框架封装的uni.request，直接使用没游封装的uni.request()进行请求数据

  /*** 下载---文件* 文件流下载* */downloadFapiao(fphm) {//这里是请求路径和参数的拼接（完整请求url）config.baseUrl是API的基本路径let url = config.baseUrl + "/ynpstWechatOrder/download-invoice";let data = { fphm: fphm }; //参数uni.showLoading({title: "下载中",duration: 2000,});uni.request({//uniapp的请求url: url,responseType: "arraybuffer", //这里记得设置响应数据格式，不然预览的pdf是空白data: data,method: "post", //请求方式header: {"content-type": "application/json",},success: (response) => {if (!response) {uni.showToast({title: "下载失败",duration: 2000,});}let pdfData = response.data; //pdfData是后端返回的文件流//创建blob数据流，并用a标签来下载let blob = new Blob([pdfData], {type: "application/pdf;charset=UTF-8",});var a = document.createElement("a");document.body.appendChild(a);a.style = "display: none";var url = window.URL.createObjectURL(blob);a.href = url;a.download = `发票${fphm}.pdf`;a.click();a.remove();window.URL.revokeObjectURL(url);uni.hideLoading(); //关闭loadinguni.showToast({title: "下载成功",duration: 2000,});},ail: (err) => {console.log(err);},});},