Android :: Load HTML File To WebView With Custom CSS

I have a WebView on my Android application which loads (WebView.loadUrl()) different local HTML files from phone's internal storage. I would like to include some custom css styles for them, Now, I could have my app edit every HTML file and add linking reference for the CSS file.I could also read the file contents, add the CSS linking and use WebView.loadData() to load it.But is it possible to do this a lot simpler and efficiently.Note: The HTML files are downloaded from a website. So editing them manually is not possible in this case, but once downloaded they can be edited via the app if necessary.