如何获取该元素在数组中的索引？

Question

I want to get the indexes of the elements in the array of production_companies if the "logo_path" of first company and the last one are null, there may be other companies for which "logo_path" is not null, I want to get their index, how can I achieve this please?

it is a movie indexing application for android the array of production_companies has a list of companies in it by default the logo of the last company on the list is displayed in the app but the condition is it should not be null but if the last one is null, then get first company on the list which is not null is displayed in the app

but if the first and last both are null, there may be others between first and last which are not, I want to get their index and get their logo displayed in my app

production_companies is the array[object] logo_path is either string or null, the string example "/q9s9KGhSsFEnpTmLLwprytB3T3d.png"

here is a sample from JSON here the first and last ones are null

{"id":68112,"logo_path":"null","name":"Studio 100 Media","origin_country":"DE"}, 
{"id":104638,"logo_path":null,"name":"Studio B Animation","origin_country":""},
{"id":20187,"logo_path":"/bYdzRm9r74bIWlSRKIWZeZyDBFD.png","name":"Flying Bark Productions","origin_country":"AU"},
{"id":45198,"logo_path":"/q9s9KGhSsFEnpTmLLwprytB3T3d.png","name":"Deutscher Filmförderfonds","origin_country":"DE"}, 
{"id":268,"logo_path":"null","name":"FilmFernsehFonds Bayern","origin_country":"DE"},
{"id":2026,"logo_path":"null","name":"FFA","origin_country":"DE"}],

// Set Studio (production_companies)
            // get the array
            try {
                // get the array
                JSONArray production_companies = jObject.getJSONArray("production_companies");
                // ensure array has at least one entry
                if (production_companies.length() > 0) {
                    // get the last element of the array as JSONObject (offset is length of array - 1)
                    JSONObject lastCompany = production_companies.getJSONObject(production_companies.length() - 1);
                    JSONObject firstCompany = production_companies.getJSONObject(0);


                    // is the "logo_path" property of lastCompany null?
                    if (lastCompany.getString("logo_path") == "null")
                    {
                        // then get first company ... i.e. offset zero
                        movie.setStudioUrl(baseUrl + MizLib.getStudioUrlSize (mContext) +
                                MizLib.getStringFromJSONObject (firstCompany, "logo_path", "")); // set the the first production company
                    }


                    // is the "logo_path" property of the firstCompany and  lastCompany are null the get the index of the one which is not null
                    if (lastCompany.getString("logo_path") == "null" && firstCompany.getString("logo_path") == "null")
                    {

                        //  Missing code here
                        
                        
                    }


                    else
                    {
                        // else logo_path is not null, so use lastCompany
                        movie.setStudioUrl(baseUrl + MizLib.getStudioUrlSize (mContext) +
                                MizLib.getStringFromJSONObject (lastCompany, "logo_path", "")); // set the last production company
                    }
                }
            } catch (JSONException e) {}

production_companies array[object]

name             string

id               integer

logo_path        string or null

origin_country   string

Answer 1

One thing that makes your code problematic is that you've mixed together code responsible for parsing JSON with business logic. If you separate those, the solution will be much simpler.

What I would suggest then is to do it in two steps.

1. Parse json into POJO classes. Looking at your data it could just be a list (or array) of companies. Company being simple java class. This step you could have done automatically using for instance GSON library.
2. Once you have all the data in java array with objects, iterate it to find the one that you're interested in (in your case having non-null logo path).

Answer 2

If you're able to add a library, add:

implementation group: 'com.jayway.jsonpath', name: 'json-path', version: '2.5.0'

and you can then do something like:

import java.util.List;

import com.jayway.jsonpath.Configuration;
import com.jayway.jsonpath.DocumentContext;
import com.jayway.jsonpath.JsonPath;
import com.jayway.jsonpath.Option;

...

Configuration cf = Configuration.builder().options(Option.SUPPRESS_EXCEPTIONS).build();
DocumentContext ctx = JsonPath.using(cf).parse(moviesJson);

String firstLogo = ctx.read("$.[0].logo_path");
String lastLogo = ctx.read("$.[-1].logo_path");

// handle "null" vs null
if( firstLogo.equals("null"))
    firstLogo = null;

if( lastLogo.equals("null"))
    lastLogo = null;

// use last logo if it's set
if( lastLogo != null )
    movie.setStudioUrl(baseUrl + MizLib.getStudioUrlSize (mContext) + lastLogo);
else if( firstLogo != null )  // last logo isn't set, see if we can use first
    movie.setStudioUrl(baseUrl + MizLib.getStudioUrlSize (mContext) + firstLogo);
else { // both are null - find the first non-null one
    List<String> someOtherLogo = ctx.read("$.[?(@.logo_path!='null' && @.logo_path!=null)].logo_path");
    // there may be more than one - get the first one
    movie.setStudioUrl(baseUrl + MizLib.getStudioUrlSize (mContext) + someOtherLogo.get(0));
}