How to get images files in externalRootDirectory

Ionic Framework
1

Hi~ guys…
I am developing now using ionic v4 with capacitor…
Please show me my developing process… check it where is wrong…

  1. file.create… => success
  2. file.write… => success
  3. file unzip(images)… => success
  4. using webView.convertFileSrc(image files in externalRootDirectory) => failure
    => convertFileSrc transfer protocol file:/// to http://
    http://localhost/_capacitor_file/storage/emulated/0/…
    Failed to load resource: … 404

What am I wrong??
I have tried that urls are same… below

  1. webView.convertFileSrc => 404
  2. capacitor.convertFileSrc => 404
  3. window.Ionic.WebView.convertFileSrc => 404