@Override
        public boolean onJsBeforeUnload(WebView view, String url, String message, JsResult result) {
            if (webChromeClient != null) {
                return webChromeClient.onJsBeforeUnload(view, url, message, result);
            }
            return super.onJsBeforeUnload(view, url, message, result);
        }
This method can be called in any thread, and if it is not called in the main thread,
it will be automatically distributed to the main thread.

@param url
@param additionalHttpHeaders
app/src/main/java/com/example/jingbin/webviewstudy/view/WVJBWebView.java