jsinterface.java

public class WebViewGUI extends Activity {
  WebView mWebView;
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    mWebView=new WebView(this);
    mWebView.getSettings().setJavaScriptEnabled(true);
    mWebView.addJavascriptInterface(new JavaScriptInterface(), "jsinterface");
    mWebView.loadUrl("file:///android_asset/www/index.html");
    setContentView(mWebView);
  }

  final class JavaScriptInterface {
    JavaScriptInterface () { }
    public String getSomeString() {
      return "string";
    }
  }
}