Question

I currently have the following code which uses a ZipInputStream instance to decompress a zip file to a target location on the phone:

ZipInputStream zipInputStream = new ZipInputStream(new FileInputStream(sourceZipFile));
ZipEntry zipEntry = null;

while ((zipEntry = zipInputStream.getNextEntry()) != null) {
  File zipEntryFile = new File(targetFolder, zipEntry.getName());
  // write contents of 'zipEntry' to 'zipEntryFile'
}

Does anyone know whether it is possible (using the setup above or otherwise) to get (an estimate of) the total number of files or bytes to be unzipped before commencing so that I can display a progress indicator as the decompression proceeds? I thought ZipInputStream might have a getTotalEntries() or similar method but I can’t find anything like this.

Answer 1

Use the ZipEntry#getSize() method. It returns the size of uncompressed file.

If you have more than one entry (file) inside ZIP file, just iterate through them first (without extracting them), and add together all file sizes. This might be a pretty good estimate.

Note, that if you need to know the exact number of bytes those files will occupy on disk, you will also need to know the exact size of a cluster in your filesystem.