Android ArrayList to Multidimensional ArrayList

Question

In my project i have a array list like this :

{"data": 
[
{"Title": "Fiat 500", "Url":"http://lh5.ggpht.com/-wgCH-P1bWCo/UWW_eCUXsVI/AAAAAAAMaKI/MlRF0GzwF8Y/s1200/Fiat-Abarth-500-US-6%25255B2%25255D.jpg"},
{"Title": "Alfa Romeo", "Url": "http://i.auto-bild.de/ir_img/1/2/4/5/4/9/7/Alfa-Romeo-4C-Spider-Vorstellung-und-Preis-1200x800-24a91d418ddbd1fa.jpg"},
{"Title": "500L", "Url":"http://cdn1.autoexpress.co.uk/sites/autoexpressuk/files/fiat-500-turbo-front-action.jpg"},
{"Title": "Egea", "Url":"https://pbs.twimg.com/media/C6vp_VcU4AAaM0t.jpg"},
{"Title": "Maserati", "Url":"http://lh4.ggpht.com/-CjXVq7s2roU/U06cyjInzjI/AAAAAAAQwvI/xuJUZ0BbOUw/s1200/Maserati-Centennial-1%25255B2%25255D.jpg"},
{"Title": "Lancia", "Url":"http://lh6.ggpht.com/_FoXyvaPSnVk/TWl73Gr0lmI/AAAAAAAECw0/ZK7nAKZ6mdY/s1200/Lancia-Chrysler-30%5B5%5D.jpg"},
{"Title": "Jeep", "Url":"http://lh3.ggpht.com/-1UvJYZn4fR0/UyGvPSDIrZI/AAAAAAAQdR0/s2c70tIu1i0/s1200/Jeep-2%25255B3%25255D.jpg"},
{"Title": "Ferrari", "Url":"http://fm.cnbc.com/applications/cnbc.com/resources/img/editorial/2016/02/05/103366052-1957s.jpg?v=1454698344"},
{"Title": "Alfa Romeo", "Url":"http://lh3.ggpht.com/-lYmpe0bGJko/UnqlBB040wI/AAAAAAAO4yE/HbUaH9RxWR8/s1200/Alfa-Romeo-Gloria-Concept-by-IED-1%25255B4%25255D.jpg"},
{"Title": "Maserati", "Url":"http://zonderpump.com/images/maserati-granturismo-sport-can-you-feel-it2.jpg"}
]
}

and i want to add items like this however viewpager and adapter get one item only. So i want to make my ArrayList dimentional and set text like this : textview.setText(list.getUsername[0 or 1]);

how can i do this. Thanks much. By the way i found this code :

function listToMatrix(list, elementsPerSubArray) {
    var matrix = [], i, k;

    for (i = 0, k = -1; i < list.length; i++) {
        if (i % elementsPerSubArray === 0) {
            k++;
            matrix[k] = [];
        }

        matrix[k].push(list[i]);
    }

    return matrix;
}

var matrix = listToMatrix([1, 2, 3, 4, 4, 5, 6, 7, 8, 9], 3);
// result: [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

but how can i make this arraylist items.?

Answer 1

It looks like your data is in JSON format; then you should rather look into existing technologies; not only for parsing; but also for "how to model my data"; see here as starting point.

But to answer your actual question - let's look into different options.

First, your own suggestion a two-dim list. That would look like:

List<List<String>> matrix = new ArrayList<>();
// and then for each row (giving you code that creates similar data)
List<String> row = new ArrayList<>();
row.add("Title");
row.add("Fiat 500"); ...

matrix.add(row);

The idea: you create such row lists for each input line; and then you add those rows to your matrix list.

But when you have a closer look you find that the first and third column are a "key" for the second/forth column. So a better fit could be:

List<Map<String, String>> matrix = new ArrayList<>();
// and then for each row (giving you code that creates similar data)
Map<String, String> row = new HashMap<>();
row.put("Title", "Fiat 500"); ...
matrix.add(row);

Meaning: you use a data structure that preserves that mapping between first and second column for example.

Finally, so far we were using "flat" data structures. But we could instead build a special class, like:

public class CarPictureInfo {
  private final String title;
  private final URL url;

  public CarPictureInfo(String title, URL url) ...

And now you create a List<CarPictureInfo> objects; and use the data of one row to create one CarPictureInfo object. (please note: I suggested here to not store that URL as "raw" String, but to convert it into a type that has more meaning than well, a raw string).

These options have different advantages and disadvantages; and in the end it depends on what you want to do with your data to understand which solution best fits your needs.