Android: use a global object instead of creating new ones

Question

I have a class A in my Android app where I have some methods. Those methods are public and used in other classes (B, C, D, E, F ...).

Is there a possibility to create only once the object from the class A and then use it in the other classes or i have to create new object in each classe.

Actually I have to do in each classe (B, C, D, E, F ...)

A a = new A();
a.xxxx;

It will be great if I can create only once the object a and then call it in my other classes.

thank you.

score 6 · Answer 1 · answered Apr 12 '12 at 12:20

6

Use a singleton pattern. It allows you to use the same instance across classes:

http://www.javabeginner.com/learn-java/java-singleton-design-pattern

answered Apr 12 '12 at 12:20

soren.qvist

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score 3 · Accepted Answer · answered Apr 12 '12 at 12:21

3

class A{
    static A a;
    static{
          a = new A();
    }
}

In every other class use

A.a to get the object and call respective methods as
A.a.xxxx()

answered Apr 12 '12 at 12:21

Chandra Sekhar

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I need now the context in my class A to instantiate te object inside and this is not an activity... – Milos Cuculovic Apr 12 '12 at 12:40
@Ana I think you should see http://stackoverflow.com/questions/5339941/android-how-to-use-getapplication-and-getapplicationcontext-from-non-activity – Chandra Sekhar Apr 12 '12 at 13:02

waqaslam · Answer 3 · 2012-04-12T12:25:03.467

2

Use static methods's analogy to do this.

For example:

public class Helper{
    public static void doSomething(){
        //do something here
    }
}

Now in your other classes, use the above method as below:

Helper.doSomething();

Or Singleton pattern would be an alternate too.

edited Apr 12 '12 at 12:25

answered Apr 12 '12 at 12:19

waqaslam

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ngesh · Answer 4 · 2012-04-12T12:22:05.970

1

Instead of that why don't you make those methods static or consider single instance pattern if there are no states involved..

how to use static methods and singleton pattern

edited Apr 12 '12 at 12:22

answered Apr 12 '12 at 12:15

ngesh

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Thank you @sandy, can you please give me some more precisions about this? – Milos Cuculovic Apr 12 '12 at 12:20
static methods are generally discouraged as a bad idea for most purposes, as they make your design harder to change later. The singleton pattern is probably a better solution here. – Jules Apr 12 '12 at 12:25
@Jules.. If there are no states involved why not..? Easy to access.. and simple code... – ngesh Apr 12 '12 at 12:26
@Jules.. read this http://stackoverflow.com/questions/752758/is-using-a-lot-of-static-methods-a-bad-thing – ngesh Apr 12 '12 at 12:29
Thank you @sandy, I will try this. One more question, what if I need the context in my A class and this is not an activity? – Milos Cuculovic Apr 12 '12 at 12:50
If consider making it a Single Instance.. then You can take Context as its argument in **getInstane()** method.. or if you go with statics i think you need to add Context argument to all methods which needs it.. – ngesh Apr 12 '12 at 12:54

user387184 · Answer 5 · 2012-04-12T12:57:39.820

I see the following 3 possibilities:

1. If these are just "normal" helper methods you may also just do

class B extends A

and inherit the methods of A into B,C,D,E,....

2. However if you need internal memory of class A which is global to all other classes or their instances of B,C,D then may use the static pattern like

class A{

static int myGlobalIntVariable; //which is accessible from everywhere 
static void myHelperMethod1() {

}

or 3. Also you may use singleton as mentioned above which creates an instance that you use everywhere.

Just as a remark, you may use singleton or static pattern depending what you prefer when accessing the methods.

For static patter you have to call them like:

A.myHelperMethod();

and for singleton you have to do:

A.getSingleton().myHelperMethod1();  or A.singleton.myHelperMethod1()

if you have defined a variable called singleton within Class A

Which one to use really depends on your needs and taste :-)

Android: use a global object instead of creating new ones

5 Answers5