can I call instance method of a static member from within static context?

Question

I have the following code:

private static AppWidgetService mInstance = null;

public static void startRefresh() {

        AppWidgetProvider.setRefreshingState(mInstance
                .getApplicationContext());
        AppWidgetManager.refreshHandler(mInstance.getApplicationContext());
    }

It sometimes fails in runtime, and sometimes passes.

for the obviuse exception:

cannot call a non-static method from a static context

I'm confused as mInstance is static,

so its instance methods could be called from a static context. no?

then how come if sometimes fails?

definitely. You can call static or non static methods of AppWidgetService, but the methods 'setRefreshingState()' and 'refreshHandler()' are static. So either you remove static from your method header or call these methods using instances of these classes. — Farrukh Chishti
– Farrukh Chishti, Commented Aug 22, 2013 at 9:28
I dont get it. startRefresh is static so it can call setRefreshingState()' and 'refreshHandler()' which are also static. Why do you suggest So either you remove static from your method header or call these methods using instances of these classes. — Elad Benda
– Elad Benda, Commented Aug 22, 2013 at 9:31
are you sure the calls to startRefresh are the problem? Those should be fine. However, your mInstance variable might be uninitialized? — codeling
– codeling, Commented Aug 22, 2013 at 12:31

BenMorel · Accepted Answer · 2013-12-13 11:05:40Z

1

From a static function, you can call only static function or use static variable. The linking is done at run time. So, though your compilation will be fine but at run time it will fail when call is made. Try making your function non static if you want to make that call.

OR

The only way to call a non-static method from a static method is to have an instance of the class containing the non-static method. By definition, a non-static method is one that is called ON an instance of some class, whereas a static method belongs to the class itself.

edited Dec 13, 2013 at 11:05

BenMorel

37k52 gold badges208 silver badges339 bronze badges

answered Aug 22, 2013 at 9:09

Sushil

8,5683 gold badges46 silver badges75 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Elad Benda Over a year ago

not yet. according to this, it should never fail on runtime. but it does sometimes

Elad Benda Over a year ago

please see my new revised question: stackoverflow.com/questions/18377150/…

Farrukh Chishti · Accepted Answer · 2013-08-22 09:22:05Z

0

This problem arises when you call a static method from a non-static block/method. In your code both 'setRefreshingState()' and 'refreshHandler()' are static methods. To call theses methods you have to remove static from your method definition.

answered Aug 22, 2013 at 9:22

Farrukh Chishti

8,56711 gold badges44 silver badges69 bronze badges

1 Comment

Elad Benda Over a year ago

please see my new revised question: stackoverflow.com/questions/18377150/…

Collectives™ on Stack Overflow

can I call instance method of a static member from within static context?

2 Answers 2

2 Comments

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related