I am displaying a html in a custom activity with a webview. I am overriding
public boolean shouldOverrideUrlLoading(WebView view, String url) {
There is a dirty hack:
Bind some Java object so that it can be called from Javascript with WebView:
addJavascriptInterface(javaObjectExposed, "JSname")
Force execute javascript within an existing page by
WebView.loadUrl("javascript:window.JSname.passData("some data");");
Described here: http://lexandera.com/2009/01/extracting-html-from-a-webview/
Note: this is a security risk - any JS code in this web page could access/call your binded Java object. Best to pass some one-time cookies to loadUrl() and pass them back your Java object to check that it's your code making the call.