Singleton class Arraylist is empty

Asked Jul 31 '17 at 19:37

Active Jul 31 '17 at 19:45

Viewed 354 times

I have created a singleton ArrayList class in android which is following.

public class SingletonArrayList  {

    private static SingletonArrayList mInstance;
    private ArrayList<String> userNameList = null;

    public static SingletonArrayList getInstance() {
        if(mInstance == null)
            mInstance = new SingletonArrayList();
        return mInstance;
    }

    private SingletonArrayList() {
        userNameList = new ArrayList<String>();
    }

    // retrieve array from anywhere
    public ArrayList<String> getArray() {
        return this.userNameList;
    }

    //Add element to array
    public void addToArray(String value) {
        userNameList.add(value);
    }
}

I'm calling this singleton ArrayList in my activity2. It's working fine there(it contains data!).

activty2:

ArrayAdapter adapter = new ArrayAdapter(this, android.R.layout.simple_list_item_1, SingletonArrayList.getInstance().getArray());

But in activtiy1 it's returing an empty list.

activity1:

Log.i("single",SingletonArrayList.getInstance().getArray().toString());

if(SingletonArrayList.getInstance().getArray().contains(username1)) {
    Toast.makeText(getApplicationContext(), "Username already Exists. Please select a different username", Toast.LENGTH_LONG).show();
    return;
}

Basically, the problem is that ArrayList is coming empty in one activity and contains data in another activity. Any solutions?

edited Jul 31 '17 at 19:45

Avijit Karmakar

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asked Jul 31 '17 at 19:37

user3094279

1

Where are the calls to `addToArray()`? – Al Lelopath Jul 31 '17 at 19:44
I'm calling this in activity2 in the onChildAdded method of firebase SingletonArrayList.getInstance().getArray().add(userClassObj.getFullName()); – user3094279 Jul 31 '17 at 19:47
1

Then why would you expect it to be populated in activity1? – Al Lelopath Jul 31 '17 at 19:49
i can use simpe add instead addToArray right? – user3094279 Jul 31 '17 at 19:50
I think you need to read about passing data between activities: https://stackoverflow.com/questions/2091465/how-do-i-pass-data-between-activities-in-android-application – Al Lelopath Jul 31 '17 at 19:51
3

This does not look like a good candidate for a singleton. – Louis Wasserman Jul 31 '17 at 19:52
what i want to achieve is to access and update the arraylist values in multiple activties. so what do you suggest i should be doing here to acheive this? And I can't use Intent – user3094279 Jul 31 '17 at 19:58
Then you probably need to persist your data – GVillani82 Jul 31 '17 at 20:03

Singleton class Arraylist is empty

0 Answers0