HarmonyOS 鸿蒙Next处理接口返回的pdf文档流并预览

参考demo：

import { common } from '[@kit](/user/kit).AbilityKit';
import { fileIo } from '[@kit](/user/kit).CoreFileKit';
import { hilog } from '[@kit](/user/kit).PerformanceAnalysisKit';
import { BusinessError, request } from '[@kit](/user/kit).BasicServicesKit';

[@Entry](/user/Entry)
[@Component](/user/Component)
struct PDFTestPage {
 private controller: pdfViewManager.PdfController = new pdfViewManager.PdfController();

 aboutToAppear(): void {
   let context = getContext() as common.UIAbilityContext;
   let dir: string = context.filesDir

   let filePath: string = dir + "/pdf.pdf";
   fileIo.accessSync(filePath);

   request.downloadFile(context, {
     url: 'https:/xxxxxxx',
     filePath: filePath
   }).then((downloadTask: request.DownloadTask) => {
     //开启回调
     downloadTask.on('complete', async () => {
       this.controller.registerPageCountChangedListener((pageCount: number) => {
         hilog.info(0x0000, 'registerPageCountChanged-', pageCount.toString());
       });
       await this.controller.loadDocument(filePath);
     })
   }).catch((err: BusinessError) => {
     console.error(`Invoke downloadTask failed-----, code is ${err.code}, message is ${err.message}`);
   });
 }

 build() {
   Row() {
     PdfView({
       controller: this.controller,
       pageFit: pdfService.PageFit.FIT_WIDTH,
       showScroll: true
     })
       .id('pdfview_app_view')
       .layoutWeight(1);
   }
   .width('100%')
   .height('100%')
 }
}