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.

• Selvin: 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>

Answer 1

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

Answer 2

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();

Answer 3

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