SharedPreferences clears itself when the app opens

Question

I've added SharedPreferences to my HomeActivity.java, in order to save IDs for shopping cart. This is the code which I've initialized for it in HomeActivity.java, which is the launcher activity:

SharedPreferences cartItems = getSharedPreferences("AddedItems", Context.MODE_PRIVATE);
SharedPreferences.Editor editor = cartItems.edit();
if (cartItems.getStringSet("AddedItems", null) == null){
    Set<String> cart = new HashSet<String>();
    editor.putStringSet("AddedItems", cart);
    editor.apply();
} else {
    Set<String> cart = cartItems.getStringSet("AddedItems", null);
}

As you can see, the code supposed to check if cartItems.getStringSet("AddedItems", null) is exist. If it does exist, then it sets cart to the contents of cartItems.getStringSet("AddedItems", null), but if it doesn't exist, then it defines cart as a new HashSet<String> and adds it to cartItems SharedPreferences.

For some reason, it is probably thinks that cartItems.getStringSet("AddedItems") does equal to null, so it resets it every time the app opens and the IDs in cart aren't being saved.

This is how I add ID to the SharedPreferences:

HomeActivity.cart.add(productId);
HomeActivity.editor.putStringSet(HomeActivity.AddedItems, HomeActivity.cart);
HomeActivity.editor.apply();

How can I fix that so It won't reset cartItems.getStringSet("AddedItems") every time the app opens?

Answer 1

Try this :

SharedPreferences cartItems = getSharedPreferences("AddedItems", Context.MODE_PRIVATE); SharedPreferences.Editor editor = cartItems.edit();

    if (Storedata != null){
        editor.putStringSet("AddedItems", Storedata);
        editor.commit();
    } else {
        Set<String> cart = cartItems.getStringSet("AddedItems", null);
    }

Storedata is the ID's of cart you want to save.

Check this for your reference: http://androidopentutorials.com/android-sharedpreferences-tutorial-and-example/