gistfile1.txt

private void loadWebPage(final String pageUrl) {
        webView.getSettings().setJavaScriptEnabled(true);
        webView.setWebChromeClient(new WebChromeClient());
        webView.setWebViewClient(new WebViewClient() {
            @Override
            public void onPageFinished(final WebView view, final String url) {
                injectJS(view);
            }
        });
        webView.loadUrl(pageUrl);
    }

  private void injectJS(final WebView view) {
        String jsContent = "";
        try {
            final InputStream inputStream = getAssets().open("script.js");
            final InputStreamReader inputStreamReader = new InputStreamReader(inputStream);
            final BufferedReader buffer = new BufferedReader(inputStreamReader);

            String line;
            while ((line = buffer.readLine()) != null) {
                jsContent += line;
            }
            inputStream.close();
        } catch (Exception e) {
            throw new RuntimeException("Cannot read file" + e.getMessage());
        }
        view.loadUrl("javascript:(" + jsContent + ")()");
    }