Android: create String Array from JSON Object

Question

I'm trying to create a image gallery in my app. I've got the images in JSON and I'd like to create a String Array from the JSON Objects in an AsyncTask so I can pop the String Array into Universal Image Loader. I think I've got the AsyncTask correctly getting the strings, but I'm stumped as to how to put the strings in an Array ie. images[] and imageDescriptions[]. My JSON looks like this:

    { 
"gallery" :
        [
           {
              "id":"0001",
              "galleryurl":"http://www.mysite.com/apps/wcbc/images/building0001.jpg",
              "gallerydescr":"image description 1"
           },
           {
              "id":"0002",
              "galleryurl":"http://www.mysite.com/apps/wcbc/images/building00011.jpg",
              "gallerydescr":"image description 2"
           }
    ]
}

and I want the resulting images[] to look like this:

public static final String[] IMAGES = new String[] {

        "http://www.mysite.com/apps/wcbc/images/building0001.jpg",
        "http://www.mysite.com/apps/wcbc/images/building00011.jpg"
};

And here's my AsyncTask class where I want to parse the JSON into the String[]:

    private class DownloadJSON extends AsyncTask<Void, Void, Void> {

    @Override
    protected Void doInBackground(Void... params) {
        galleryArrList = new ArrayList<HashMap<String, String>>();
        JGrid4Adapter jParser = new JGrid4Adapter();
        // getting JSON string from URL
        JSONObject jsonOb = jParser.getJSONFromUrl(jsonUrl);            
        try {
            JSArrGallery = jsonOb.getJSONArray(TAG_GALLERY);
            // looping through All gallery images
            for (int i = 0; i < JSArrGallery.length(); i++) {
                JSONObject galleryJO = JSArrGallery.getJSONObject(i);
                String idStr = galleryJO.getString(TAG_ID);
                String urlStr = galleryJO.getString(TAG_GALLERYURL);
                String descrStr = galleryJO.getString(TAG_GALLERYDESCR);
                //-- How to create String Array at this point?


            }// -- END for loop
        } catch (JSONException e) {
            e.printStackTrace();
        }// --- END Try
        return null;
    }

    @Override
    protected void onPostExecute(Void args) {
        //--- do stuff here

    }

}

Any help would be cool.

but this is bad idea ... better use some own class(or rather array/list of them) like class container { string id; string whatever; string someotherprop;} or at least array/list of Map<String, ObjectOrString> — Selvin
– Selvin, Commented Jan 3, 2014 at 15:13

Nambi · Accepted Answer · 2014-01-03 15:16:30Z

By Using Array

String AidStr[]=new String();
String  AurlStr[]=new String();
String AdescrStr[]=new String();

for (int i = 0; i < JSArrGallery.length(); i++) {
                        JSONObject galleryJO = JSArrGallery.getJSONObject(i);
                        String idStr = galleryJO.getString(TAG_ID);
                        String urlStr = galleryJO.getString(TAG_GALLERYURL);
                        String descrStr = galleryJO.getString(TAG_GALLERYDESCR);
                        //-- How to create String Array at this point?
                         AidStr[i]=idStr;
                         AurlStr[i]=urlStr;
                         AdescStr[i]=descrStr;


           }// -- END for loop

or

By Using ArrayList

    ArrayList<String> AidStr=new ArrayList<String>();
    ArrayList<String> AurlStr=new ArrayList<String>();
    ArrayList<String>AdescrStr =new ArrayList<String>();


            for (int i = 0; i < JSArrGallery.length(); i++) {
                            JSONObject galleryJO = JSArrGallery.getJSONObject(i);
                            String idStr = galleryJO.getString(TAG_ID);
                            String urlStr = galleryJO.getString(TAG_GALLERYURL);
                            String descrStr = galleryJO.getString(TAG_GALLERYDESCR);
                            //-- How to create String Array at this point?
                             AidStr.add(idstr);
                             AurlStr.add(urlStr);
                             AdescStr.add(descrStr);


                    }// -- END for loop

Phil · Accepted Answer · 2014-01-03 15:19:47Z

You need to have a way to retrieve the String array from your AsyncTask. To do this, make these changes to your code:

private class DownloadJSON extends AsyncTask<Void, Void, Object[]> {//-------THIS LINE

    private Callback callback;//---THIS LINES

    public DownloadJSON(Callback callback) {//---THESE LINES
        this.callback = callback;
    }

    @Override
    protected Void doInBackground(Void... params) {
        galleryArrList = new ArrayList<HashMap<String, String>>();
        JGrid4Adapter jParser = new JGrid4Adapter();
        // getting JSON string from URL
        JSONObject jsonOb = jParser.getJSONFromUrl(jsonUrl);            
        try {
            JSArrGallery = jsonOb.getJSONArray(TAG_GALLERY);
            // looping through All gallery images
                            String[] imagesArray = new String[JSArrGallery.length()];//------THIS LINE
                            String[] descriptionsArray = new String[JSArrGallery.length()];//------THIS LINE TOO
            for (int i = 0; i < JSArrGallery.length(); i++) {
                JSONObject galleryJO = JSArrGallery.getJSONObject(i);
                String idStr = galleryJO.getString(TAG_ID);
                String urlStr = galleryJO.getString(TAG_GALLERYURL);
                String descrStr = galleryJO.getString(TAG_GALLERYDESCR);
                imagesArray[i] = urlStr;//-------THIS LINE
                descriptionsArray[i] = descrStr;//----THIS LINE TOO

            }// -- END for loop
            return new Object[]{imagesArray, descriptionsArray};//----THIS LINE
        } catch (JSONException e) {
            e.printStackTrace();
        }// --- END Try
        return null;
    }

    @Override
    protected void onPostExecute(Object[] args) {
        //---THESE LINES
        if (args == null)
            callback.call(null, null);
        else
            callback.call(args[0], args[1]);
    }

    //-----THESE LINES
    public interface Callback {
        public void call(String[] imageURLs, String[] imageDescriptions);
    }

}

Finally, to bring this all together, do:

new DownloadJSON(new DownloadJSON.Callback() {
    public void call(String[] imageURLs, String[] imageDescriptions) {
        //TODO handle these arrays now
    }
}).execute();

ρяσѕρєя K · Accepted Answer · 2014-01-03 15:24:40Z

0

Use JSArrGallery.length() to initialize IMAGES Array before adding element in Array as:

        JSArrGallery = jsonOb.getJSONArray(TAG_GALLERY);
         IMAGES=new String[JSArrGallery.length()];  //<< initialize array here
        for (int i = 0; i < JSArrGallery.length(); i++) {
             //..your code to get image url fom JSONObject...

             // add url to Array
           IMAGES[i]=urlStr;

           }

instead of Array use ArrayList for Storing images url if JSONArray size is dynamic

answered Jan 3, 2014 at 15:24

ρяσѕρєя K

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