我无法在ionic 3中打开pdf文件

npm install -g ionic cordova

ionic cordova plugin add cordova-plugin-file-opener2
npm install @ionic-native/file-opener@4

import { FileOpener } from '@ionic-native/file-opener/ngx';

constructor(private fileOpener: FileOpener) { }

openPDF() {
  const filePath = 'path/to/your/pdf/file.pdf';
  const fileType = 'application/pdf';

  this.fileOpener.open(filePath, fileType)
    .then(() => console.log('File opened successfully'))
    .catch(err => console.error('Error opening file', err));
}

<button (click)="openPDF()">打开PDF文件</button>