Basic WebView blocking using libadblockplus

BlockingWebViewClient.java

import java.io.File;
import java.util.regex.Pattern;

import org.adblockplus.android.ABPEngine;
import org.adblockplus.libadblockplus.FilterEngine.ContentType;

import android.content.Context;
import android.webkit.WebResourceResponse;
import android.webkit.WebView;
import android.webkit.WebViewClient;

public class BlockingWebViewClient extends WebViewClient
{
  private ABPEngine engine;

  private static final Pattern RE_JS = Pattern.compile("\\.js$", Pattern.CASE_INSENSITIVE);
  private static final Pattern RE_CSS = Pattern.compile("\\.css$", Pattern.CASE_INSENSITIVE);
  private static final Pattern RE_IMAGE = Pattern.compile("\\.(?:gif|png|jpe?g|bmp|ico)$", Pattern.CASE_INSENSITIVE);
  private static final Pattern RE_FONT = Pattern.compile("\\.(?:ttf|woff)$", Pattern.CASE_INSENSITIVE);
  private static final Pattern RE_HTML = Pattern.compile("\\.html?$", Pattern.CASE_INSENSITIVE);

  public void start(Context context)
  {
    final File basePath = context.getFilesDir();
    this.engine = ABPEngine.create(context, ABPEngine.generateAppInfo(context),
        basePath.getAbsolutePath());

    // Additional steps may be required here, i.e. :
    // - subscription selection or updating
    // - maybe also setting other options (like AcceptableAds)
    // It might also be a good idea to delay the first calls until
    // everything is loaded, have a look at AndroidFilterChangeCallback
    // and ABPEngine.create()
  }

  @Override
  public WebResourceResponse shouldInterceptRequest(WebView view, String url)
  {
    // Determine the content
    ContentType contentType = null;
    if (RE_JS.matcher(url).find())
    {
      contentType = ContentType.SCRIPT;
    }
    else if (RE_CSS.matcher(url).find())
    {
      contentType = ContentType.STYLESHEET;
    }
    else if (RE_IMAGE.matcher(url).find())
    {
      contentType = ContentType.IMAGE;
    }
    else if (RE_FONT.matcher(url).find())
    {
      contentType = ContentType.FONT;
    }
    else if (RE_HTML.matcher(url).find())
    {
      contentType = ContentType.SUBDOCUMENT;
    }
    else
    {
      contentType = ContentType.OTHER;
    }
    // Check if we should block ... we sadly do not have the referrer chain here,
    // might also be hard to get as we do not have HTTP headers here
    if (engine.matches(url, contentType, new String[0]))
    {
      // If we should block, return empty response which results in a 404
      return new WebResourceResponse("text/plain", "UTF-8", null);
    }
    // Otherwise, continue by returning null
    return null;
  }
}