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Re: How to access properties of a class from another class?

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On 7/28/2015 3:45 PM, Xue Feng wrote:
> Hi,
>
> Beg your pardon for this silly question.I am familiar with the concept
> of encapsulation indeed. However, for some problems, I think there must
> be better solutions.
>
> My question comes from a feature of Netbeans which is well-known for its
> wonderful GUI design facilities. However, for all GUI components,
> Netbeans likes to cram them into a single source file of the main frame.
> A direct result for this is all code pertain to definition of GUI
> component objects and event handling are concentrated in a source file,
> and it meants to flate rapidly. For large-scale projects, this is not a
> good idea.(I have only little experience with Netbeans for two weeks.
> There mybe other options I don't know. Tell me please.)

     Speaking for myself, I prefer to write plain Java code to build
my Swing UI's.  I've tried NetBeans' GUI builder but found it tedious:
To accomplish what four lines of code would have done, NetBeans requires
me to click and scroll and tab from menu to menu to menu -- and even
with all that, I need to look at the generated code to be sure I haven't
forgotten to click something!

     I have (occasionally) used the GUI builder to create a dummy or
mock-up of my UI, just to see how something unfamiliar is done.  For
example, I find some of the newer layout managers quite intricate and
hard to use.  So, I'll make a dummy UI in the builder and then study the
generated code; with a working example in front of me it's then much
easier to write what I actually wind up using.

     But that's just my personal taste; others may differ.

> To practice MVC schema, it is necessary to design separate control class
> and view class. Both of them have occasions to interact with GUI
> components. However, all of components are defined in the main frame
> class as private members. Therefore, control class and view class need
> to access these components encapsulated in the main frame class. I think
> there mybe some ways to achieve the goal as follows:

     As an aside, note that Swing doesn't use a "pure" MVC architecture.
Roughly speaking, it combines V and C to get an "M+VC" architecture.
<http://www.oracle.com/technetwork/java/architecture-142923.html> has
a more detailed explanation.

> (1) Define control class and veiw class as inner class of the main frame
> class. But, this practice will result in a huge souce file obviously.

     Sounds like an unattractive solution.

> (2) Define components as public members. However, it seems that Netbeans
> does not allow this way.

     You *can* change the access for a component: Select the component,
go to the Code tab on the Properties menu, find the Variable Modifiers
line, click on the ... button, click on the Access drop-down of the
dialog that opens, choose "public", and click on OK.  (That's the sort
of thing that makes me complain about finding the GUI builder "tedious"
to use: Instead of six keystrokes p u b l i c, I must do at least six
separate mouse actions in three sub-windows.  I'm a poor typist, but
even so I can type p u b l i c much more quickly and easily than I can
get through all this clickety-clacking!)

     Besides, making everything public seems a poor idea to begin with.

> (3) Define many 'get' methods for the main frame class, and invoke them
> from  control class and view class to get references of component
> needed. This is an ordinary pratice, but somewhat tedious. Moreover, it
> also lacks flexibility especially when the GUI design changes frequently.

     Using public access would suffer from the same lack of flexibility.

> (4) Take some language construct such as friend class from C++. I don't
> konw whether Java has this kind of construct.

     Not really, but sometimes "package-private" access (that's what you
get if you don't use any of public, protected, or private) will serve.
It means that any other class in the same package can see (and touch!)
the component, which seems rather permissive -- but since you're the
person who decides what's in your package, you can limit the exposure.

> (5) Is there any way to dynamically generate an object at runtime in
> terms of the main frame class as template? This object wraps up all
> components' reference as its public member. Then, pass the object to
> control object and view object. Maybe reflection can help, but I am not
> sure about it.

     I'm not sure what you're proposing here, so I won't comment.

     I'm sorry I can't help you more with the GUI builder -- but, as I
said, my experiences of using it have not been happy.  It's tedious to
use, and I don't like the code it generates any more than you seem to.
Perhaps you'll learn to use it more smoothly than I have managed ...

-- 
esosman@comcast-dot-net.invalid
"Don't be afraid of work. Make work afraid of you." -- TLM

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Thread

How to access properties of a class from another class? Xue Feng <xf.lotus@yahoo.com> - 2015-07-29 03:45 +0800
  Re: How to access properties of a class from another class? Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-07-28 16:58 -0400
  Re: How to access properties of a class from another class? Jeff Higgins <jeff@invalid.invalid> - 2015-07-28 16:59 -0400
  Re: How to access properties of a class from another class? Nigel Wade <nmw@ion.le.ac.uk> - 2015-07-29 15:24 +0100
    Re: How to access properties of a class from another class? Xue Feng <xf.lotus@yahoo.com> - 2015-08-01 16:10 +0800

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