Java：共享增量变量

Question

I am making a blackberry application I need to share a common variable in my application between different entry points. The variable is a simple count which keeps track of the amount of notifications on the icon home screen. Every time the scheduled background application updates it will increment the count variable which is then used by setValue(count) to display it. Someone suggested to use the singleton and runtimestore approach. I was searching around for this method and found a code snippet on a forum:

Integer i = new Integer(0);
RuntimeStore.getInstance().put(ID, i);
i.setValue(7);

//On other module:
Integer i = (Integer) RuntimeStore.getInstance().get(ID);

My issue is that I still do not know how to properly utilize this code, I have also looked at

http://docs.blackberry.com/en/developers/deliverables/17952/CS_creating_a_singleton_by_using_rutnime_store_1554335_11.jsp

but I am not sure how to implement that in my code. I am trying to increment the variable iconCount which needs to be kept consistent amonst the background and foreground processes (ie if the user checks the app, the notification alerts will be reset to 0).

public void setVisible1(boolean visible, int count) {
    if (_indicator != null) {
        if (visible) {
            _indicator.setVisible(true);
            _indicator.setValue(++count);   //incrementing count
            UserInterface.iconCount++;      // also trying here
        } else {
            _indicator.setVisible(false);
        }
    }
}

Using RuntimeStore.getInstance().put(GUID, countsIcon); in my UserInterface class creates errors probably because I am either using it wrong or not in the correct location. I've only recently started blackberry development and Java so this is very new to me. I have attached the main portion of my code below if it is of any assistance.

Again thanks for any help, it would be greatly appreciated!

---

public class UserInterface extends UiApplication {
        static int iconCount;  //stores the value of the icon number
        public static void main(String[] args) {
        if (args != null && args.length>0 && "startVibrate".equals(args[0])){
            scheduleVibrate();
        }
        else{
            UserInterface theApp = new UserInterface();
            theApp.enterEventDispatcher();
        }
    }
    static MyAppIndicator SV = new MyAppIndicator();
    private static void scheduleVibrate()
    {
        SV.setVisible1(true,iconCount);
        Alert.startVibrate(2550); 
        ApplicationDescriptor current =     ApplicationDescriptor.currentApplicationDescriptor();
        current.setPowerOnBehavior(ApplicationDescriptor.DO_NOT_POWER_ON);
        ApplicationManager manger = ApplicationManager.getApplicationManager();
        manger.scheduleApplication(current,System.currentTimeMillis()+1000,true);
    }
    public UserInterface() {
        pushScreen(new UserInterfaceScreen());
    }
}


public class MyAppIndicator{

public ApplicationIndicator _indicator; 
public static MyAppIndicator _instance; 

MyAppIndicator () {
    setupIndicator();
}
public static MyAppIndicator getInstance() {
    if (_instance == null) {
        _instance = new MyAppIndicator ();
    }
    return(_instance);
}
public void setupIndicator() {

    //Setup notification 
    if (_indicator == null) {
        ApplicationIndicatorRegistry reg = ApplicationIndicatorRegistry.getInstance();
        _indicator = reg.getApplicationIndicator();

        if(_indicator == null) {
            ApplicationIcon icon = new ApplicationIcon(EncodedImage.getEncodedImageResource ("notificationsdemo_jde.png"));
            _indicator = reg.register(icon, false, true);  
            _indicator.setValue(0);
            _indicator.setVisible(false);
        }
    }
}

public void setVisible1(boolean visible, int count) {
    if (_indicator != null) {
         if (visible) {
            _indicator.setVisible(true);
            _indicator.setValue(++count);   //incrementing count
            UserInterface.iconCount++;      // also trying here
        } else {
            _indicator.setVisible(false);
        }
    }
}

Answer 1

A static variable is all you need, but it seems like you already have one(iconCount). If it isn't working the way you want, you might want to try creating another class that keeps track of the iconCount with a static variable that can be accessed from the classes you want to have access to it.

Answer 2

Have a read throug the RIM article on singletons . As they say, static variables are initialized for each process. Use the Runtimestore to ensure that all processes access the one, singleton object.

I was going to edit the code into here, but it was easier for me to put it up on my blog: http://www.hrbuckley.net/2012/01/using-singleton-classes-in-blackberry.html

Answer 3

Simply create a class, put that variable in that class and extend this class in every other class where you want to access the variable. Modify the value of the counter variable in any of the class it will automatically be reflected in other classes. Don't forget to declare it static