Convert Android Cursor to ArrayList of arrays

Question

I try to convert my Cursor data to a arraylist<String[]>. But at the end all the data in the arraylist is overwrited with the last row. What do i do wrong?

Cursor c = myDbHelper.getLvl1Cata();
String[] data = new String[3];
c.moveToFirst();
while(!c.isAfterLast()) {
    data[0] = Integer.toString(c.getInt(0));
    data[1] = c.getString(1);
    data[2] = Integer.toString(c.getInt(2));
    Log.e("cc", data[1]);
    catalogueData.add(data);
    c.moveToNext();
}

LarsH · Accepted Answer · 2016-11-22 17:46:20Z

12

Try this

Cursor c = myDbHelper.getLvl1Cata();
String[] data;
if (c != null) {
    while(c.moveToNext()) {
        data = new String[3]; // Note this addition
        data[0] = Integer.toString(c.getInt(0));
        data[1] = c.getString(1);
        data[2] = Integer.toString(c.getInt(2));
        Log.e("cc", data[1]);
        catalogueData.add(data);
    }
    c.close();
}

data is an array of strings. In the original code, you added the same array to your catalogueData structure several times. You changed the value of the array's contents each time, but it was still the same array object. So you ended up with catalogueData holding several references to a single array, and that array can only have one value for data[0]: the last thing you set it to.

This answer fixes that by using a new and different array for each row in the cursor.

edited Nov 22, 2016 at 17:46

LarsH

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answered Sep 12, 2011 at 13:32

WarrenFaith

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5 Comments

Anupam Over a year ago

Hey Waren, I was also doing the same thing, I'm getting error at catalogueData.add(data);, what exactly is that? Please can you guide me through this.

WarrenFaith Over a year ago

@Anupam you need to tell me what the error is, otherwise I can't help.

Shivam Agrawal Over a year ago

@WarrenFaith Is there any way to read the cursor and store in the array list in one go. If i don't want to run the loop ?

WarrenFaith Over a year ago

@ShivamAgrawal No. The cursor is just a pointer to data and you need to move it by yourself. So looping is the only chance.

azwar_akbar Over a year ago

@Anupam catalogueData.add(data); is adding data to arraylist catalogueData. catalogueData variable should be List or ArrayList or something similiar to it.

HBhatia · Accepted Answer · 2014-12-01 18:38:48Z

1

Try this:

if(mycursor!=null){    
            do{
    TextView name = (TextView)view.findViewById(R.id.contact_name);               
    name.setText(cursor.getString(cursor.getColumnIndex
                (Displayname)));
    mycursor.moveToNext();
            }while (mycursor.isLast());
        }

edited Dec 1, 2014 at 18:38

HBhatia

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answered Apr 10, 2014 at 13:32

Disha

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Comments

DeeV · Accepted Answer · 2011-09-12 13:31:49Z

0

Put String[] data = new String[3]; into the while loop. You're overwriting the array object with each iteration.

answered Sep 12, 2011 at 13:31

DeeV

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4 Comments

WarrenFaith Over a year ago

creating a new object in a loop is bad practice in android! See my answer where declaration and initialization is done in two steps.

LarsH Over a year ago

@WarrenFaith: Can you clarify what you mean about creating a new object in a loop? Your answer also creates a new object in a loop, although you do separate declaration of the variable from creating the object.

DeeV Over a year ago

@LarsH: His answer would perform the exact same as mine. It doesn't matter where the declaration is put. If you want to save a collection of Arrays, you have to create a new set of Arrays at each iteration or else the previous one will just overwrite the last set.

DeeV Over a year ago

Otherwise if you were just throwing the array away at each iteration then yes, that would be true. You'd want to create the object outside the loop.

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