I have worked around this issue by creating a local HTML file that contains javascript to create and submit a form.
If I open this file in the Webview it automatically submits the contents of a form to the external webpage using a HTTP POST.
Here’s the HTML:
\<HTML\>\<HEAD\> \<script\> function postwith (to,p) { var myForm = document.createElement("form"); myForm.method="post" ; myForm.action = to ; for (var k in p) { var myInput = document.createElement("input") ; myInput.setAttribute("name", k) ; myInput.setAttribute("id", k) ; myInput.setAttribute("value", p[k]); myForm.appendChild(myInput) ; } document.body.appendChild(myForm) ; myForm.submit() ; document.body.removeChild(myForm) ; }; function sendMyData() { var params = { username: "info@springmorning.nl", password: "MyPassword", appversion: "0.1.00a"} var action = "https://springmorningstuff.nl/"; postwith(action,params); }; \</script\> \</HEAD\> \<BODY onload="sendMyData()"\>forwarding\</BODY\> \</HTML\>