Question

I currently have code to share a variable between two entry points in my application. The variable is the iconCount variable used to indicate how many notices the user has which is displayed on the home screen beside the icon. The way I’ve managed to do this is with a singleton and it (seems) to work fine at the moment. The issue is now that I do not want those notices to reset to zero when I completely turn off and turn on the phone. Should there be 7 notifications, I want there to be 7 notifications even after a device restart. For this I apparently need a persistent store integration which I’ve researched for a while.

So far my code for the bare singleton is:

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); //UserInterface.incrementCount()
            } else {
                _indicator.setVisible(false);
            }
        }
    }
}

I have been using the blackberry tutorial to figure out how to implement the persistable storage: http://supportforums.blackberry.com/t5/Java-Development/Storing-persistent-data/ta-p/442747

Now before I go any further I must stress I’m very new to java development so my coding might be completely wrong, but here is what I’ve tried to do:

public void setVisible1(boolean visible, int count) {

    if (_indicator != null) {
        if (visible) {
            _indicator.setVisible(true);
            _indicator.setValue(count); //UserInterface.incrementCount()
            StoreInfo info = new StoreInfo(); 
            info.incElement();

            synchronized (persistentCount) { 
                //persistentCount.setContents(_data); 
                persistentCount.commit(); 
            } 


        } else {
            _indicator.setVisible(false);
        }
    }
}

static { 
    persistentCount = PersistentStore.getPersistentObject(0xdec6a67096f833cL); 
    synchronized (persistentCount) { 
        if (persistentCount.getContents() == null) { 
            persistentCount.setContents(new Vector()); //don't know what to do with this?
            persistentCount.commit(); 
        } 
    } 
} 

private static final class StoreInfo implements Persistable{
    private int iconCount;
    public StoreInfo(){}

    public int getElement(){
        return (int)iconCount;
    }

    public void incElement(){
        iconCount++;             //persistently increment icon variable
    }

    public void resetElement(){
            iconCount=0;             //when user checks application
    }
}   

The code above doesn’t work which I’d expect somehow because I’m having trouble implementing the persistent portion. If anyone has any idea or input on how to accomplish this any assistance would be helpful. And of course thanks in advance.

Answer 1

In the example they have a variable called _data that holds the StoreInfo class, so first of all you should be keeping the StoreInfo in some variable. To do this have something like the following in your static initializer:

persistentCount = PersistentStore.getPersistentObject(0xdec6a67096f833cL); 
synchronized (persistentCount) { 
    if (persistentCount.getContents() == null) { 
        persistentCount.setContents(new StoreInfo());
        persistentCount.commit(); 
    } 
}  
_data = (StoreInfo)persistentCount.getContents();

Now when you want to update it and save to the PersistentStore you can have something like:

_data.incElement();
synchronized(persistentCount) {
    persistentCount.setContents(_data);
    persistentCount.commit();
}

Assuming you’re going to only ever have one instance of StoreInfo it could be better to put the commit code into the modifier methods so you don’t forget to save the new values to the PersistentStore.