Android check if value equals to the values in Array

Question

I have a ArrayList tokens; I am adding values to the array with a listView click. Before i add the value to array i check if the value already exist array. I remove the value is it exists else i will add the the value

This is how i have done, but the values are not being added to the array

ArrayList<String> tokens;
tokens = new ArrayList<String>();
...
....
public void onItemClick(AdapterView<?> listView, View view,
                            int position, long id) {
        Cursor cursor = (Cursor) listView.getItemAtPosition(position);
        String selectedtoken = cursor.getString(cursor.getColumnIndexOrThrow("ContactToken"));

        for (int i = 0; i < tokens.size(); i++) {
                if (tokens.get(i).equals(id_To_Search)) {
                    tokens.remove(i);
                }
                else {
                    tokens.add(selectedtoken );
                }
            }
    }
...
...
Log.i("array: ", tokens.toString()); // No values in the array

i would suggest use a set and then convert the set to the arraylist when you are done,it would be much easier — Pramod Yadav, Nov 02 '15 at 13:55

Alexander Kulyakhtin · Answer 1 · 2015-11-02T14:10:03.810

4

You are not adding when you initially have 0 tokens.

Change to:

boolean removed = false;
for (Iterator<String> iter = tokens.iterator(); iter.hasNext(); ) {
    if (iter.next().equals(id_To_Search)) {
        iter.remove();
        removed = true;
    }
}
if(!removed) {
   tokens.add(selectedtoken);
}

edited Nov 02 '15 at 14:10

answered Nov 02 '15 at 13:55

Alexander Kulyakhtin

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2

That will fail with a ConcurrentModificationException in many cases... and it will *always* have the selected token at the end. – Jon Skeet Nov 02 '15 at 13:59
I've corrected the 2nd but the 1st ehhh, it all on the UI thread – Alexander Kulyakhtin Nov 02 '15 at 14:02
1

Just because it's in one thread doesn't mean you won't get a `ConcurrentModificationException`. See https://stackoverflow.com/questions/223918 – Jon Skeet Nov 02 '15 at 14:03
Actually, my mistake - you're not using an enhanced for loop, so you won't get that error. But you *will* skip over entries at the moment. (If you remove entry 0, you're then not going to look at the "new" entry 0...) – Jon Skeet Nov 02 '15 at 14:07
Thank you, I've changed in accordance. – Alexander Kulyakhtin Nov 02 '15 at 14:10

frogatto · Answer 2 · 2015-11-02T14:14:42.807

3

You can simply check the existence using contains method.

if(!tokens.contains(id_To_Search)){
    tokens.add(selectedtoken);
} else {
    tokens.remove(selectedtoken);
}

edited Nov 02 '15 at 14:14

answered Nov 02 '15 at 13:59

frogatto

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score 3 · Answer 3 · answered Nov 02 '15 at 14:00

You're checking for each element in your array if it's the item you're going to store/delete, and then doing the proper operation.

You should find first if you're element exists in the whole array, and then adding or deleting it.

Try something like this:

public void onItemClick(AdapterView<?> listView, View view,
                        int position, long id) {
    Cursor cursor = (Cursor) listView.getItemAtPosition(position);
    String selectedtoken = cursor.getString(cursor.getColumnIndexOrThrow("ContactToken"));

            if (tokens.contains(id_To_Search)) {     
               tokens.remove(id_To_Search);

            }
            else {
                tokens.add(id_To_Search);
            }
}

score 2 · Answer 4 · answered Nov 02 '15 at 13:57

If your list is empty, you never go into the loop, so you'll never call add. If you do have any tokens to start with, you're either adding or removing the new token for each existing token which isn't what you want.

I suspect you want:

int existingIndex = tokens.indexOf(selectedToken);
if (existingIndex == -1) {
   tokens.add(selectedToken);
} else {
   tokens.remove(existingIndex);
}

Alternatively, you could use a Set<String> with:

// Speculatively try to remove it... and add it if you couldn't remove
boolean removed = tokens.remove(selectedToken);
if (!removed) {
   tokens.add(selectedToken);
}

Also note that you're currently testing for id_To_Search but then adding selectedToken - this answer assumes you actually meant to use selectedToken in both places.

score 1 · Answer 5 · answered Nov 02 '15 at 13:57

1

The for loop will not execute when tokens.size() is 0. So you'll never add a token because initially the token list is empty.

answered Nov 02 '15 at 13:57

Bunny Rabbit

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Android check if value equals to the values in Array

5 Answers5