This error occurs when the ImeOptions is set to EditorInfo.IME_ACTION_NEXT or EditorInfo.IME_ACTION_PREVIOUS. While the parent of that view is not focusable, or the next found focus object is not focusable.
It calls to find the next focus item that should be quickly jumped to but this does not exist or isn’t focusable, it throws this error. It will happen if the next is hidden and thus not focusable or the parent cannot actually deal with the findFocus() call and returns null.
The solution thusly is rather easy. Don’t set it to IME_ACTION as next in this case. If you can’t quickly jump from text field to text field then either make that doable or switch the action to being DONE.
edittext.setImeOptions(EditorInfo.IME_ACTION_DONE);
Note the comment in the code before the offending bit:
This is the handling for some default action. Note that for backwards
compatibility we don’t do this default handling if explicit ime
options have not been given, instead turning this into the normal
enter key codes that an app may be expecting.
It won’t do this if you set the edittext type or if you give an explicit IME that isn’t functionally wrong. Or have a parent object that is focusable on the next or anything else. It’s only legacy code in a fallback bit that might sometimes not have the given action as possible.