WebViewUtils.java

 public static void callJavaScriptFunction(final WebView webView, final String script) {
    if (webView == null) {
      return;
    }
    webView.post(new Runnable() {
      @Override
      public void run() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
          webView.evaluateJavascript(script, new ValueCallback<String>() {
            @Override
            public void onReceiveValue(String value) {

            }
          });
        } else {
          webView.loadUrl("javascript:" + script);
        }
      }
    });
  }