How to decode a JSON Array on Android

Question

The need to decode a JSON Array thus:

output: [ [{ }, { }], [{ }, { }] ]

I was doing it in a way that decoded a Array that way:

output: [{ }, { }, { }]

Code of how I was doing:

_{Method to convert to Entity}

private CardapioEntities convertCardapio(JSONObject obj) throws JSONException {
    String titulo = obj.getString(TAG_TITULO);
    String descricao = obj.getString(TAG_DESCRICAO);
    String preco = obj.getString(TAG_PRECO);
    String tipo = obj.getString(TAG_TIPO);

    return new CardapioEntities(titulo, descricao, preco, tipo);
}

_{Method to add Listview}

private void _getCardapio(String result) {
    //...
    try {
        JSONArray json = new JSONArray(result);
        for (int i = 0; i < json.length(); i++) {
                //...
                cardapioEntities.setCardapioPreco(convertCardapio(json.getJSONObject(i)).getCardapioPreco());
                listaLanches.add(cardapioEntities);
        }
        //...
        final ListView lvLanches = (ListView) findViewById(R.id.lvLanches);
        lvLanches.setAdapter(new CustomListAdapter(this, listaLanches));
        //...
    } catch (JSONException e) {
        e.printStackTrace();
    }
}

Question:

How to adapt this code to read the Json Array? Exemplify.

EDITION:

In accordance with the reply of @Wakim, another question arose: Why is the object repeating in the ListView? I think it’s Logic’s mistake.

private void _getCardapio(String result) {
    //...
    try {
        JSONArray json = new JSONArray(result);
        for (int i = 0; i < json.length(); i++) {
            CardapioEntities cardapioEntities = new CardapioEntities();
            JSONArray arrayDentroDoArray = json.getJSONArray(i);
            for (int j = 0; j < arrayDentroDoArray.length(); j++) {
                JSONObject objeto = arrayDentroDoArray.getJSONObject(j);

                if (convertCardapio(objeto).getCardapioTipo() == 0) {
                    cardapioEntities.setCardapioTitulo(convertCardapio(objeto).getCardapioTitulo());
                    cardapioEntities.setCardapioDescricao(convertCardapio(objeto).getCardapioDescricao());
                    cardapioEntities.setCardapioPreco(convertCardapio(objeto).getCardapioPreco());
                    listaLanches.add(cardapioEntities);
                }
            }
        }
    } catch (JSONException e) {
        e.printStackTrace();
    }
}

Answer 1

To fetch a Array within a JSONArray is through the method getJSONArray.

Using your method:

private void _getCardapio(String result) {
    //...
    try {
        JSONArray json = new JSONArray(result);

        for (int i = 0; i < json.length(); i++) {
            //...

            // Agora voce possui um determinado array na posicao i
            JSONArray arrayDentroDoArray = json.getJSONArray(i);

            // Itera sobre cada objeto do array interno
            for(int j = 0; j < arrayDentroDoArray.length(); ++j) {
                JSONObject objeto = arrayDentroDoArray.getJSONObject(j);
                // Usar o objeto
            }

            //cardapioEntities.setCardapioPreco(convertCardapio(json.getJSONObject(i)).getCardapioPreco());
            //listaLanches.add(cardapioEntities);
        }
        //...
        final ListView lvLanches = (ListView) findViewById(R.id.lvLanches);
        lvLanches.setAdapter(new CustomListAdapter(this, listaLanches));
        //...
    } catch (JSONException e) {
        e.printStackTrace();
    }
}

Watch out because if the position guy i is not a Array he will launch a JSONException. What you could do, if you’re not sure, is:

Object o = json.get(i);

if(o instanceof JSONArray) {
    // Trabalhar com o Array
} else if(o instanceof JSONObject) {
    // Trabalhar com o objeto
}

Answer 2

I think these links will help you in your doubt!

http://www.devmedia.com.br/trabalhando-com-json-em-java-o-pacote-org-json/25480

https://stackoverflow.com/questions/1568762/accessing-members-of-items-in-a-jsonarray-with-java

https://stackoverflow.com/questions/18983185/how-to-create-correct-jsonarray-in-java-using-jsonobject

more would be something like:

 //string json: contém array com três elementos
    String json_str = "{\"elenco\":[\"Json Leigh\", \"Mary Stylesheet\",  \"David Markupovny\"]}";

    //instancia um novo JSONObject passando a string como entrada
    JSONObject my_obj = new JSONObject(json_str);

    //recupera o array "elenco"  
    JSONArray elenco = my_obj.getJSONArray("elenco");