@Nullable
  private File getCachedFile(String url) throws FileNotFoundException {
    File jsonFile = new File(parentDir(), filenameForUrl(url, FileExtension.JSON, false));
    if (jsonFile.exists()) {
      return jsonFile;
    }
    File zipFile = new File(parentDir(), filenameForUrl(url, FileExtension.ZIP, false));
    if (zipFile.exists()) {
      return zipFile;
    }
    File gzipFile = new File(parentDir(), filenameForUrl(url, FileExtension.GZIP, false));
    if (gzipFile.exists()) {
      return gzipFile;
    }
    return null;
  }
Returns the cache file for the given url if it exists. Checks for both json and zip.
Returns null if neither exist.
lottie/src/main/java/com/airbnb/lottie/network/NetworkCache.java