for anyone facing this issue:

​

In yuor project navigate to the URL the error is giving, in my case:

platforms\android\app\src\main\java\org\apache\cordova\filetransfer\FileTransfer.java

​

1. In the imports replace 'Whitelist' with 'Allowlist'

​

example: 

import org.apache.cordova.Whitelist; => import org.apache.cordova.AllowList;

​

2. around line 690 replace 'Whitelist' with 'Allowlist' inside de conditional:

    Boolean shouldAllowRequest = null;

        if (isLocalTransfer) {

            shouldAllowRequest = true;

        }

        if (shouldAllowRequest == null) {

            try {

                Method gwl = webView.getClass().getMethod("getWhitelist");

                'Whitelist' whitelist = ('Whitelist')gwl.invoke(webView);

                shouldAllowRequest = whitelist.isUrl'WhiteListed'(source);

            } catch (NoSuchMethodException e) {

            } catch (IllegalAccessException e) {

            } catch (InvocationTargetException e) {

            }

        }

  Example:

       old:

            try {

                Method gwl = webView.getClass().getMethod("getWhitelist");

                Whitelist whitelist = (Whitelist)gwl.invoke(webView);

                shouldAllowRequest = whitelist.isUrlWhiteListed(source);

            } catch (NoSuchMethodException e) {....

       new:

            try {

                Method gwl = webView.getClass().getMethod("getWhitelist");

                AllowList whitelist = (AllowList)gwl.invoke(webView);

                shouldAllowRequest = whitelist.isUrlAllowListed(source);

            } catch (NoSuchMethodException e) {.....

plugin repository:      

https://github.com/Priyansu431/cordova-plugin-file-transfer.git