Fields (be they JFrame
s or any other type) are not owned by classes but by instances. Unless you want your Activity
subclasses to be singletons (meaning they have exactly one instance), the answer to your first question is "no".
More importantly though, multiple JFrame
s in a single application is certainly not what you want. If you want every subclass to have its own way to acquire input, then probably a JTextField
(to embeddded in the main frame) and otherwise a JDialog
(corresponding to a separate window) would do the trick.