android - How to insert one more item in a json existing structure with gson? -

the code below generates correctly first structure of json file.

gson = new gsonbuilder().setprettyprinting().create();  auddetheader auddetheader = new auddetheader();  //arraylist<orderdetail> auddetlist = new arraylist<orderdetail>(); map<string, auddet> auddetlist = new hashmap<string, auddet>();  auddet auddet = new auddet(); auddet.setlineid("1"); auddet.setitemnumber("abc"); auddet.setquantity(9); auddet.setprice(10.00);  list<string> phones = new arraylist<string>();                    phones.add("24530001"); phones.add("24530002"); phones.add("24530003");              auddet.setphones(phones);                 auddetlist.put("teste 2", auddet);               auddetheader.setauddetlist(auddetlist);  gson gson = new gsonbuilder().setprettyprinting().create(); string jsonstring = gson.tojson(auddetheader);  bufferedwriter bufferedwriter = null; try {      file file = new file(environment.getexternalstoragedirectory() + "/download/test/test.json");     if(!file.exists()){         file.createnewfile();     }      filewriter filewriter = new filewriter(file);     bufferedwriter = new bufferedwriter(filewriter);     bufferedwriter.write(jsonstring);   } catch (ioexception e) {     e.printstacktrace(); } {     try {         if (bufferedwriter != null){             bufferedwriter.close();         }     } catch (ioexception ex) {         ex.printstacktrace();     } } 

the result of code:

{   "results": {     "teste 2": {       "itemnumber": "abc",       "lineid": "1",       "phones": [         "24530001",         "24530002",         "24530003"       ],       "price": 10.0,       "quantity": 9     }   } } 

i want add new item. desire stay structure below.

{    "results":{       "teste 2":{          "itemnumber":"abc",          "lineid":"1",          "phones":[             "24530001",             "24530002",             "24530003"          ],          "price":10.0,          "quantity":9       },       "teste 3":{          "itemnumber":"def",          "lineid":"2",          "phones":[             "30303030",             "40404040",             "505050"          ],          "price":11.0,          "quantity":12       }    } } 

the auddetheader.class

public class auditoriadetalheheader {  @serializedname("results") private map<string, auditoriadetalhe> auditoriadetalhelist;     ... } 

the auddet.class

public class auditoriadetalhe {   string lineid = null;  string itemnumber = null;  int quantity = 0;  double price = null;  list<string> phones = new arraylist<string>();      ... } 

worked me code!!!

main class

private static file filejson = new file(environment.getexternalstoragedirectory() + "/download/test/test.json");  @override public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.teste_criajson);  createjsonstructure();  button btnsave = (button)findviewbyid(r.id.btsave);  btnsalvar.setonclicklistener( new view.onclicklistener() {     public void onclick(view v) {          try {             string strfilejson = getstringfromfile(filejson.tostring());                         jsonobject jsonobj = new jsonobject(strfilejson);             gson gson = new gson();             jsonparser jsonparser = new jsonparser();             string idaud = "10";              auddet ad = new auddet();             ad.setlineid("2");             ad.setitemnumber("def");             ad.setquantity(22);             ad.setprice(22.22);              list<string> phones = new arraylist<string>();                                phones.add("22");             phones.add("22");             phones.add("22");                            ad.setphones(phones);                     string jsonstr = jsonparser.parse(gson.tojson(ad)).tostring();             jsonobject jsonobject = new jsonobject(jsonstr);             jsonobj.getjsonobject("results").put(idaud, jsonobject);              writejsonfile(filejson, jsonobj.tostring());          } catch (exception e1) {             e1.printstacktrace();         }       } }); 

if not exists json file, create basic structure insert itens.

public static void createjsonstructure(){     if(!filejson.exists()){                  try {             filejson.createnewfile();              string jsonstring = "{\"results\":{}}";              writejsonfile(filejson, jsonstring);                          } catch (ioexception e) {             e.printstacktrace();         }     } } 

open json file string format, , prepare insert new item:

public static string getstringfromfile (string filepath) throws exception {     file fl = new file(filepath);     fileinputstream fin = new fileinputstream(fl);     string ret = convertstreamtostring(fin);     //make sure close streams.     fin.close();             return ret; } public static string convertstreamtostring(inputstream is) throws exception {     bufferedreader reader = new bufferedreader(new inputstreamreader(is));     stringbuilder sb = new stringbuilder();     string line = null;     while ((line = reader.readline()) != null) {       sb.append(line).append("\n");     }     return sb.tostring(); } 

writes json file exists:

public static void writejsonfile(file file, string json)  {     bufferedwriter bufferedwriter = null;     try {          if(!file.exists()){             file.createnewfile();         }          filewriter filewriter = new filewriter(file);         bufferedwriter = new bufferedwriter(filewriter);         bufferedwriter.write(json);      } catch (ioexception e) {         e.printstacktrace();     } {         try {             if (bufferedwriter != null){                 bufferedwriter.close();             }         } catch (ioexception ex) {             ex.printstacktrace();         }     } }