android在将json对象从url解析到listview时遇到nullpoint异常

我试图解析json对象以将其填充到列表视图中，但我遇到了一些问题，请提供帮助

JSONParser jParser = new JSONParser();

            // getting Json String from url

            JSONArray json = jParser.getJSONFromUrl(url);


                // getting array of books

               //Get rid of this = book = json.getJSONArray(TAG_BOOK);

            // looping through all books

                 for(int i=0;i<json.length();i++){
                try{
                JSONObject parent = json.getJSONObject(i);
                JSONObject c  = parent.optJSONObject("camera");
                if(c == null)
                    c = parent.optJSONObject("book");
                if(c == null)
                    c = parent.optJSONObject("music");
                // storing each json item in variable

                String title = c.getString(TAG_TITLE);
                String price = c.getString(TAG_PRICE);
                String authors = c.getString(TAG_AUTHORS);
                String id = c.getString(TAG_ID);
                String description = c.getString(TAG_DESCRIPTION);
                // creating new HashMap
                HashMap<String, String> map = new HashMap<String, String>();

                map.put(TAG_ID, id);
                map.put(TAG_TITLE, title);
                map.put(TAG_PRICE, price);
                map.put(TAG_AUTHORS, authors);
                map.put(TAG_DESCRIPTION, description);

                bookList.add(map);

            }

            catch (JSONException e) {
                e.printStackTrace();    

            }
            }

我得到了NullpointerException

JSONParser jParser = new JSONParser();

            // getting Json String from url

            JSONArray json = jParser.getJSONFromUrl(url);


                // getting array of books

               //Get rid of this = book = json.getJSONArray(TAG_BOOK);

            // looping through all books

                 for(int i=0;i<json.length();i++){
                try{
                JSONObject parent = json.getJSONObject(i);
                JSONObject c  = parent.optJSONObject("camera");
                if(c == null)
                    c = parent.optJSONObject("book");
                if(c == null)
                    c = parent.optJSONObject("music");
                // storing each json item in variable

                String title = c.getString(TAG_TITLE);
                String price = c.getString(TAG_PRICE);
                String authors = c.getString(TAG_AUTHORS);
                String id = c.getString(TAG_ID);
                String description = c.getString(TAG_DESCRIPTION);
                // creating new HashMap
                HashMap<String, String> map = new HashMap<String, String>();

                map.put(TAG_ID, id);
                map.put(TAG_TITLE, title);
                map.put(TAG_PRICE, price);
                map.put(TAG_AUTHORS, authors);
                map.put(TAG_DESCRIPTION, description);

                bookList.add(map);

            }

            catch (JSONException e) {
                e.printStackTrace();    

            }
            }

这是我的全部代码：

JSONParser jParser = new JSONParser();

            // getting Json String from url

            JSONArray json = jParser.getJSONFromUrl(url);


                // getting array of books

               //Get rid of this = book = json.getJSONArray(TAG_BOOK);

            // looping through all books

                 for(int i=0;i<json.length();i++){
                try{
                JSONObject parent = json.getJSONObject(i);
                JSONObject c  = parent.optJSONObject("camera");
                if(c == null)
                    c = parent.optJSONObject("book");
                if(c == null)
                    c = parent.optJSONObject("music");
                // storing each json item in variable

                String title = c.getString(TAG_TITLE);
                String price = c.getString(TAG_PRICE);
                String authors = c.getString(TAG_AUTHORS);
                String id = c.getString(TAG_ID);
                String description = c.getString(TAG_DESCRIPTION);
                // creating new HashMap
                HashMap<String, String> map = new HashMap<String, String>();

                map.put(TAG_ID, id);
                map.put(TAG_TITLE, title);
                map.put(TAG_PRICE, price);
                map.put(TAG_AUTHORS, authors);
                map.put(TAG_DESCRIPTION, description);

                bookList.add(map);

            }

            catch (JSONException e) {
                e.printStackTrace();    

            }
            }

我正在解析来自以下url的数据

JSONParser jParser = new JSONParser();

            // getting Json String from url

            JSONArray json = jParser.getJSONFromUrl(url);


                // getting array of books

               //Get rid of this = book = json.getJSONArray(TAG_BOOK);

            // looping through all books

                 for(int i=0;i<json.length();i++){
                try{
                JSONObject parent = json.getJSONObject(i);
                JSONObject c  = parent.optJSONObject("camera");
                if(c == null)
                    c = parent.optJSONObject("book");
                if(c == null)
                    c = parent.optJSONObject("music");
                // storing each json item in variable

                String title = c.getString(TAG_TITLE);
                String price = c.getString(TAG_PRICE);
                String authors = c.getString(TAG_AUTHORS);
                String id = c.getString(TAG_ID);
                String description = c.getString(TAG_DESCRIPTION);
                // creating new HashMap
                HashMap<String, String> map = new HashMap<String, String>();

                map.put(TAG_ID, id);
                map.put(TAG_TITLE, title);
                map.put(TAG_PRICE, price);
                map.put(TAG_AUTHORS, authors);
                map.put(TAG_DESCRIPTION, description);

                bookList.add(map);

            }

            catch (JSONException e) {
                e.printStackTrace();    

            }
            }

JSONParser jParser = new JSONParser();

            // getting Json String from url

            JSONArray json = jParser.getJSONFromUrl(url);


                // getting array of books

               //Get rid of this = book = json.getJSONArray(TAG_BOOK);

            // looping through all books

                 for(int i=0;i<json.length();i++){
                try{
                JSONObject parent = json.getJSONObject(i);
                JSONObject c  = parent.optJSONObject("camera");
                if(c == null)
                    c = parent.optJSONObject("book");
                if(c == null)
                    c = parent.optJSONObject("music");
                // storing each json item in variable

                String title = c.getString(TAG_TITLE);
                String price = c.getString(TAG_PRICE);
                String authors = c.getString(TAG_AUTHORS);
                String id = c.getString(TAG_ID);
                String description = c.getString(TAG_DESCRIPTION);
                // creating new HashMap
                HashMap<String, String> map = new HashMap<String, String>();

                map.put(TAG_ID, id);
                map.put(TAG_TITLE, title);
                map.put(TAG_PRICE, price);
                map.put(TAG_AUTHORS, authors);
                map.put(TAG_DESCRIPTION, description);

                bookList.add(map);

            }

            catch (JSONException e) {
                e.printStackTrace();    

            }
            }

解析数据的代码

 public class JSONParser {

static InputStream is = null;
static JSONObject jObj = null;
static String json = "";

public JSONParser(){

}

public JSONObject getJSONFromUrl(String url){

//making Http request
try{
//default httpclient    
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);

HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();

}
    catch (UnsupportedEncodingException e) {
    e.printStackTrace();
    }
catch (ClientProtocolException e) {
    e.printStackTrace();

}
catch(IOException e){
    e.printStackTrace();
    }
    try{
        BufferedReader reader = new BufferedReader(new InputStreamReader(
                is, "iso-8859-1"), 8);

        StringBuilder sb = new StringBuilder();
        String line = null;
        while ((line = reader.readLine()) != null) {
            sb.append(line + "\n");
        }
        is.close();
        json = sb.toString();
    } 
catch (Exception e) {
        Log.e("Buffer Error", "Error converting result " + e.toString());
    }

    // try parse the string to a JSON object
    try {
        jObj = new JSONObject(json);
    } catch (JSONException e) {
        Log.e("JSON Parser", "Error parsing data " + e.toString());
    }

    // return JSON String
    return jObj;

}

JSONParser jParser = new JSONParser();

            // getting Json String from url

            JSONArray json = jParser.getJSONFromUrl(url);


                // getting array of books

               //Get rid of this = book = json.getJSONArray(TAG_BOOK);

            // looping through all books

                 for(int i=0;i<json.length();i++){
                try{
                JSONObject parent = json.getJSONObject(i);
                JSONObject c  = parent.optJSONObject("camera");
                if(c == null)
                    c = parent.optJSONObject("book");
                if(c == null)
                    c = parent.optJSONObject("music");
                // storing each json item in variable

                String title = c.getString(TAG_TITLE);
                String price = c.getString(TAG_PRICE);
                String authors = c.getString(TAG_AUTHORS);
                String id = c.getString(TAG_ID);
                String description = c.getString(TAG_DESCRIPTION);
                // creating new HashMap
                HashMap<String, String> map = new HashMap<String, String>();

                map.put(TAG_ID, id);
                map.put(TAG_TITLE, title);
                map.put(TAG_PRICE, price);
                map.put(TAG_AUTHORS, authors);
                map.put(TAG_DESCRIPTION, description);

                bookList.add(map);

            }

            catch (JSONException e) {
                e.printStackTrace();    

            }
            }

}

JSONParser jParser = new JSONParser();

            // getting Json String from url

            JSONArray json = jParser.getJSONFromUrl(url);


                // getting array of books

               //Get rid of this = book = json.getJSONArray(TAG_BOOK);

            // looping through all books

                 for(int i=0;i<json.length();i++){
                try{
                JSONObject parent = json.getJSONObject(i);
                JSONObject c  = parent.optJSONObject("camera");
                if(c == null)
                    c = parent.optJSONObject("book");
                if(c == null)
                    c = parent.optJSONObject("music");
                // storing each json item in variable

                String title = c.getString(TAG_TITLE);
                String price = c.getString(TAG_PRICE);
                String authors = c.getString(TAG_AUTHORS);
                String id = c.getString(TAG_ID);
                String description = c.getString(TAG_DESCRIPTION);
                // creating new HashMap
                HashMap<String, String> map = new HashMap<String, String>();

                map.put(TAG_ID, id);
                map.put(TAG_TITLE, title);
                map.put(TAG_PRICE, price);
                map.put(TAG_AUTHORS, authors);
                map.put(TAG_DESCRIPTION, description);

                bookList.add(map);

            }

            catch (JSONException e) {
                e.printStackTrace();    

            }
            }

---

您的问题在于JSONParser。这和从站点返回的JSON格式不正确。您有一组JSONObject，其中JSONObject具有相似的名称。我做了一个快速简单的解决方案来处理它，但是如果您控制生成JSON的代码，那么我建议将项目类别（书籍、音乐、相机）分组到它们自己的JSONArray中

JSONParser jParser = new JSONParser();

            // getting Json String from url

            JSONArray json = jParser.getJSONFromUrl(url);


                // getting array of books

               //Get rid of this = book = json.getJSONArray(TAG_BOOK);

            // looping through all books

                 for(int i=0;i<json.length();i++){
                try{
                JSONObject parent = json.getJSONObject(i);
                JSONObject c  = parent.optJSONObject("camera");
                if(c == null)
                    c = parent.optJSONObject("book");
                if(c == null)
                    c = parent.optJSONObject("music");
                // storing each json item in variable

                String title = c.getString(TAG_TITLE);
                String price = c.getString(TAG_PRICE);
                String authors = c.getString(TAG_AUTHORS);
                String id = c.getString(TAG_ID);
                String description = c.getString(TAG_DESCRIPTION);
                // creating new HashMap
                HashMap<String, String> map = new HashMap<String, String>();

                map.put(TAG_ID, id);
                map.put(TAG_TITLE, title);
                map.put(TAG_PRICE, price);
                map.put(TAG_AUTHORS, authors);
                map.put(TAG_DESCRIPTION, description);

                bookList.add(map);

            }

            catch (JSONException e) {
                e.printStackTrace();    

            }
            }

您从网站返回的JSON是一个带有JSONObject的JSONArray。。你在做下面的事情

JSONParser jParser = new JSONParser();

            // getting Json String from url

            JSONArray json = jParser.getJSONFromUrl(url);


                // getting array of books

               //Get rid of this = book = json.getJSONArray(TAG_BOOK);

            // looping through all books

                 for(int i=0;i<json.length();i++){
                try{
                JSONObject parent = json.getJSONObject(i);
                JSONObject c  = parent.optJSONObject("camera");
                if(c == null)
                    c = parent.optJSONObject("book");
                if(c == null)
                    c = parent.optJSONObject("music");
                // storing each json item in variable

                String title = c.getString(TAG_TITLE);
                String price = c.getString(TAG_PRICE);
                String authors = c.getString(TAG_AUTHORS);
                String id = c.getString(TAG_ID);
                String description = c.getString(TAG_DESCRIPTION);
                // creating new HashMap
                HashMap<String, String> map = new HashMap<String, String>();

                map.put(TAG_ID, id);
                map.put(TAG_TITLE, title);
                map.put(TAG_PRICE, price);
                map.put(TAG_AUTHORS, authors);
                map.put(TAG_DESCRIPTION, description);

                bookList.add(map);

            }

            catch (JSONException e) {
                e.printStackTrace();    

            }
            }

jObj=新的JSONObject（json）

JSONParser jParser = new JSONParser();

            // getting Json String from url

            JSONArray json = jParser.getJSONFromUrl(url);


                // getting array of books

               //Get rid of this = book = json.getJSONArray(TAG_BOOK);

            // looping through all books

                 for(int i=0;i<json.length();i++){
                try{
                JSONObject parent = json.getJSONObject(i);
                JSONObject c  = parent.optJSONObject("camera");
                if(c == null)
                    c = parent.optJSONObject("book");
                if(c == null)
                    c = parent.optJSONObject("music");
                // storing each json item in variable

                String title = c.getString(TAG_TITLE);
                String price = c.getString(TAG_PRICE);
                String authors = c.getString(TAG_AUTHORS);
                String id = c.getString(TAG_ID);
                String description = c.getString(TAG_DESCRIPTION);
                // creating new HashMap
                HashMap<String, String> map = new HashMap<String, String>();

                map.put(TAG_ID, id);
                map.put(TAG_TITLE, title);
                map.put(TAG_PRICE, price);
                map.put(TAG_AUTHORS, authors);
                map.put(TAG_DESCRIPTION, description);

                bookList.add(map);

            }

            catch (JSONException e) {
                e.printStackTrace();    

            }
            }

你应该做什么

JSONParser jParser = new JSONParser();

            // getting Json String from url

            JSONArray json = jParser.getJSONFromUrl(url);


                // getting array of books

               //Get rid of this = book = json.getJSONArray(TAG_BOOK);

            // looping through all books

                 for(int i=0;i<json.length();i++){
                try{
                JSONObject parent = json.getJSONObject(i);
                JSONObject c  = parent.optJSONObject("camera");
                if(c == null)
                    c = parent.optJSONObject("book");
                if(c == null)
                    c = parent.optJSONObject("music");
                // storing each json item in variable

                String title = c.getString(TAG_TITLE);
                String price = c.getString(TAG_PRICE);
                String authors = c.getString(TAG_AUTHORS);
                String id = c.getString(TAG_ID);
                String description = c.getString(TAG_DESCRIPTION);
                // creating new HashMap
                HashMap<String, String> map = new HashMap<String, String>();

                map.put(TAG_ID, id);
                map.put(TAG_TITLE, title);
                map.put(TAG_PRICE, price);
                map.put(TAG_AUTHORS, authors);
                map.put(TAG_DESCRIPTION, description);

                bookList.add(map);

            }

            catch (JSONException e) {
                e.printStackTrace();    

            }
            }

jObj=新的JSONArray（json）

JSONParser jParser = new JSONParser();

            // getting Json String from url

            JSONArray json = jParser.getJSONFromUrl(url);


                // getting array of books

               //Get rid of this = book = json.getJSONArray(TAG_BOOK);

            // looping through all books

                 for(int i=0;i<json.length();i++){
                try{
                JSONObject parent = json.getJSONObject(i);
                JSONObject c  = parent.optJSONObject("camera");
                if(c == null)
                    c = parent.optJSONObject("book");
                if(c == null)
                    c = parent.optJSONObject("music");
                // storing each json item in variable

                String title = c.getString(TAG_TITLE);
                String price = c.getString(TAG_PRICE);
                String authors = c.getString(TAG_AUTHORS);
                String id = c.getString(TAG_ID);
                String description = c.getString(TAG_DESCRIPTION);
                // creating new HashMap
                HashMap<String, String> map = new HashMap<String, String>();

                map.put(TAG_ID, id);
                map.put(TAG_TITLE, title);
                map.put(TAG_PRICE, price);
                map.put(TAG_AUTHORS, authors);
                map.put(TAG_DESCRIPTION, description);

                bookList.add(map);

            }

            catch (JSONException e) {
                e.printStackTrace();    

            }
            }

然后，您需要将返回值更改为JSONArray，而不是JSONObject

JSONParser jParser = new JSONParser();

            // getting Json String from url

            JSONArray json = jParser.getJSONFromUrl(url);


                // getting array of books

               //Get rid of this = book = json.getJSONArray(TAG_BOOK);

            // looping through all books

                 for(int i=0;i<json.length();i++){
                try{
                JSONObject parent = json.getJSONObject(i);
                JSONObject c  = parent.optJSONObject("camera");
                if(c == null)
                    c = parent.optJSONObject("book");
                if(c == null)
                    c = parent.optJSONObject("music");
                // storing each json item in variable

                String title = c.getString(TAG_TITLE);
                String price = c.getString(TAG_PRICE);
                String authors = c.getString(TAG_AUTHORS);
                String id = c.getString(TAG_ID);
                String description = c.getString(TAG_DESCRIPTION);
                // creating new HashMap
                HashMap<String, String> map = new HashMap<String, String>();

                map.put(TAG_ID, id);
                map.put(TAG_TITLE, title);
                map.put(TAG_PRICE, price);
                map.put(TAG_AUTHORS, authors);
                map.put(TAG_DESCRIPTION, description);

                bookList.add(map);

            }

            catch (JSONException e) {
                e.printStackTrace();    

            }
            }

然后在主活动中将“json”更改为JSONArray并去掉“book”。只需循环JSONArray即可

JSONParser jParser = new JSONParser();

            // getting Json String from url

            JSONArray json = jParser.getJSONFromUrl(url);


                // getting array of books

               //Get rid of this = book = json.getJSONArray(TAG_BOOK);

            // looping through all books

                 for(int i=0;i<json.length();i++){
                try{
                JSONObject parent = json.getJSONObject(i);
                JSONObject c  = parent.optJSONObject("camera");
                if(c == null)
                    c = parent.optJSONObject("book");
                if(c == null)
                    c = parent.optJSONObject("music");
                // storing each json item in variable

                String title = c.getString(TAG_TITLE);
                String price = c.getString(TAG_PRICE);
                String authors = c.getString(TAG_AUTHORS);
                String id = c.getString(TAG_ID);
                String description = c.getString(TAG_DESCRIPTION);
                // creating new HashMap
                HashMap<String, String> map = new HashMap<String, String>();

                map.put(TAG_ID, id);
                map.put(TAG_TITLE, title);
                map.put(TAG_PRICE, price);
                map.put(TAG_AUTHORS, authors);
                map.put(TAG_DESCRIPTION, description);

                bookList.add(map);

            }

            catch (JSONException e) {
                e.printStackTrace();    

            }
            }

同时移动你的手臂，尝试进入循环

JSONParser jParser = new JSONParser();

            // getting Json String from url

            JSONArray json = jParser.getJSONFromUrl(url);


                // getting array of books

               //Get rid of this = book = json.getJSONArray(TAG_BOOK);

            // looping through all books

                 for(int i=0;i<json.length();i++){
                try{
                JSONObject parent = json.getJSONObject(i);
                JSONObject c  = parent.optJSONObject("camera");
                if(c == null)
                    c = parent.optJSONObject("book");
                if(c == null)
                    c = parent.optJSONObject("music");
                // storing each json item in variable

                String title = c.getString(TAG_TITLE);
                String price = c.getString(TAG_PRICE);
                String authors = c.getString(TAG_AUTHORS);
                String id = c.getString(TAG_ID);
                String description = c.getString(TAG_DESCRIPTION);
                // creating new HashMap
                HashMap<String, String> map = new HashMap<String, String>();

                map.put(TAG_ID, id);
                map.put(TAG_TITLE, title);
                map.put(TAG_PRICE, price);
                map.put(TAG_AUTHORS, authors);
                map.put(TAG_DESCRIPTION, description);

                bookList.add(map);

            }

            catch (JSONException e) {
                e.printStackTrace();    

            }
            }

通过这种方式，您可以对不同的类别执行不同的操作（如果需要），并将类别中的任何类似JSON对象分组在一起

JSONParser jParser = new JSONParser();

            // getting Json String from url

            JSONArray json = jParser.getJSONFromUrl(url);


                // getting array of books

               //Get rid of this = book = json.getJSONArray(TAG_BOOK);

            // looping through all books

                 for(int i=0;i<json.length();i++){
                try{
                JSONObject parent = json.getJSONObject(i);
                JSONObject c  = parent.optJSONObject("camera");
                if(c == null)
                    c = parent.optJSONObject("book");
                if(c == null)
                    c = parent.optJSONObject("music");
                // storing each json item in variable

                String title = c.getString(TAG_TITLE);
                String price = c.getString(TAG_PRICE);
                String authors = c.getString(TAG_AUTHORS);
                String id = c.getString(TAG_ID);
                String description = c.getString(TAG_DESCRIPTION);
                // creating new HashMap
                HashMap<String, String> map = new HashMap<String, String>();

                map.put(TAG_ID, id);
                map.put(TAG_TITLE, title);
                map.put(TAG_PRICE, price);
                map.put(TAG_AUTHORS, authors);
                map.put(TAG_DESCRIPTION, description);

                bookList.add(map);

            }

            catch (JSONException e) {
                e.printStackTrace();    

            }
            }

或者，如果无论是书籍、音乐还是相机，操作都是相同的，那么您可以在JSON对象中添加另一个字段作为“type”，然后在数组（JSON_array.put（））中创建JSONObject，而不使用名称，使其显示为

JSONParser jParser = new JSONParser();

            // getting Json String from url

            JSONArray json = jParser.getJSONFromUrl(url);


                // getting array of books

               //Get rid of this = book = json.getJSONArray(TAG_BOOK);

            // looping through all books

                 for(int i=0;i<json.length();i++){
                try{
                JSONObject parent = json.getJSONObject(i);
                JSONObject c  = parent.optJSONObject("camera");
                if(c == null)
                    c = parent.optJSONObject("book");
                if(c == null)
                    c = parent.optJSONObject("music");
                // storing each json item in variable

                String title = c.getString(TAG_TITLE);
                String price = c.getString(TAG_PRICE);
                String authors = c.getString(TAG_AUTHORS);
                String id = c.getString(TAG_ID);
                String description = c.getString(TAG_DESCRIPTION);
                // creating new HashMap
                HashMap<String, String> map = new HashMap<String, String>();

                map.put(TAG_ID, id);
                map.put(TAG_TITLE, title);
                map.put(TAG_PRICE, price);
                map.put(TAG_AUTHORS, authors);
                map.put(TAG_DESCRIPTION, description);

                bookList.add(map);

            }

            catch (JSONException e) {
                e.printStackTrace();    

            }
            }

[
{
"type":"camera",
"picture":"http://img5.flixcart.com/image/camera/5/p/a/nikon-d90-slr-40x40-imacxmh3y6wmqh8b.jpeg",
"model":"D90 SLR with AF-S 18-105mm VR Kit Lens",
"make":"Nikon",
"price":57182.0
},
{
"type":"book",
"description":"This book is one of a series of texts written by faculty of the Electrical Engineering and Computer Science Department at the Massachusetts Institute of Technology. It was edited and produced by The MIT Press under a joint production-distribution arrangement with the McGraw-Hill Book Company.",
"authors":"Harold Abelson and Gerald Jay Sussman with Julie Sussman",
"price":469.0,
"id":51087,
"title":"Structure and Interpretation of Computer Programs"
}
]

---

再说一遍，您应该采取的路线取决于您以后将如何处理数据

请发布LogCat错误，如果您可以读取LogCat，请指出发生NullPointerException的行。AndroidJSONParsingActivity.java中的第62行是什么？是的，您的错误率为100%，现在我没有遇到任何问题，输出是正确的正确，请你建议我将项目类别（书籍、音乐、相机）分组到各自的JSONArray中。创建一个主JSONArray。然后为每个类别创建JSONArray（即，一个用于音乐，一个用于书籍，一个用于相机）。您将使用每个JSONObject（标题、价格等）填充Category JSONArray。将所有项目添加到类别数组后，将每个类别数组作为JSON对象添加到主数组中。我编辑了我的答案，以显示我仍在尝试的格式，但你的答案对我帮助很大，我正在尝试一份工作，这是分配给我的作业。谢谢。我在哪里可以点击告诉你这个问题的答案

JSONParser jParser = new JSONParser();

            // getting Json String from url

            JSONArray json = jParser.getJSONFromUrl(url);


                // getting array of books

               //Get rid of this = book = json.getJSONArray(TAG_BOOK);

            // looping through all books

                 for(int i=0;i<json.length();i++){
                try{
                JSONObject parent = json.getJSONObject(i);
                JSONObject c  = parent.optJSONObject("camera");
                if(c == null)
                    c = parent.optJSONObject("book");
                if(c == null)
                    c = parent.optJSONObject("music");
                // storing each json item in variable

                String title = c.getString(TAG_TITLE);
                String price = c.getString(TAG_PRICE);
                String authors = c.getString(TAG_AUTHORS);
                String id = c.getString(TAG_ID);
                String description = c.getString(TAG_DESCRIPTION);
                // creating new HashMap
                HashMap<String, String> map = new HashMap<String, String>();

                map.put(TAG_ID, id);
                map.put(TAG_TITLE, title);
                map.put(TAG_PRICE, price);
                map.put(TAG_AUTHORS, authors);
                map.put(TAG_DESCRIPTION, description);

                bookList.add(map);

            }

            catch (JSONException e) {
                e.printStackTrace();    

            }
            }