Develop Reference

Parse JSON using amirdew/JSON library

I'm using amirdew/JSON library, which you can find here to parse my string to JSON.
The string I retrieved is this: https://en.wikipedia.org/w/api.php?format=json&action=query&prop=extracts&exintro=&explaintext=&titles=Portugal
This is the code I have at the moment, and it is not working and I believe that it is because of the keys...
public void ParseJson (String json){
JSON json2 = new JSON(json);
String firstTag = json2.key("query").key("pages").key("extract").stringValue();
txtInfo = findViewById(R.id.txtInfo);
txtInfo.setText(firstTag);
}
The firstTag variable is null because it can't retrieve any value. I want to retrieve the text inside "extracts". How can I do it? What keys do I need?

I suggest you to use the JSONObject which is already inside the SDK. You would use it like this:
String input = "..."; // your input
JSONObject obj = new JSONObject(input);
Strings extracts = obj.getJSONObject("query").getJSONObject("pages").getJSONObject("23033").getString("extract");

android: Retrieve values from nested JSON object into List type

I have a nested JSON array from which I need to retrieve values of all Usernames nested within Friends.
{
"Friends": [
{"Username": "abc"},
{"Username": "xyz"}
]
}
After I get all the usernames, I want to store it in a List that I will use with an adapter and ListView.
FriendList.java:
public class FriendList
{
#SerializedName("Username")
private String username;
public String getUsername()
{
return username;
}
public void setUsername(String username)
{
this.username = username;
}
}
This is the code that I have written so far:
if (httpResult != null && !httpResult.isEmpty()) //POST API CALL
{
Type listType = new TypeToken<List<FriendList>>() {}.getType();
List<FriendList> friendList = new Gson().fromJson(httpResult, listType);
FLCustomAdapter adapter = new FLCustomAdapter(getActivity(), friendList);
mainFriendsListView.setAdapter(adapter);
}
However, an error occurs: Failed to deserialize Json object.
Please suggest, what additions/changes should be made to it, so that I can retrieve nested JSON values into a list?

First of all, You have to understand the strucure of this Json.
You can see, it contains
1 . A json object
2 . This json object contains a json array which can include several different json objects or json arrays.
In this case, it contains json objects.
Parsing:
Get the Json Object first
try{
JSONObject jsonObject=new JSONObject(jsonResponse);
if(jsonObject!=null){
//get the json array
JSONArray jsonArray=jsonObject.getJSONArray("Friends");
if(jsonArray!=null){
ArrayList<FriendList> friendList=new ArrayList<FriendList>();
//iterate your json array
for(int i=0;i<jsonArray.length();i++){
JSONObject object=jsonArray.getJSONObject(i);
FriendList friend=new FriendList();
friend.setUserName(object.getString(Username));
friendList.add(friend);
}
}
}
}
catch(JSONException ex){
ex.printStackTrace();
}
hope, it will help you.

Solution with GSON.
You need to two class to parse this.
FriendList and UsernameDao.
public class UsernameDao {
#SerializedName("Username")
private String username;
//get set methods
}

Simple Json Parsing would be like this
JSONObject params=new JSONObject(httpResult);
JSONObject params1=params.getJsonObject("Friends");
JsonArray array=params1.getJsonArray();
for(int i=0;i<array.length();i++)
{
String userName=array.getJsonObject(i).getString("UserName");
// Do whatever you want to do with username
}

Following code works good without any use of GSON , Please try .
String jsonString = "Your Json Data";
JSONObject jsonRootObject = new JSONObject(jsonString );
JSONArray friendsArray = jsonRootObject .getJSONArray("Friends");
ArrayList<FriendList > friendsList = new ArrayList<FriendList >();
for(int friendsLen = 0 ;friendsLen < friendsArray .length() ; friendsLen ++){
FriendList userNameObj = new UserName();
JSONObject jsonObj = jsonRootObject.getJSONObject(friendsLen ) ;
String Username = jsonObj.getString("Username");
userNameObj .setUserName(Username );
friendsList .add(userNameObj );
}
Now friendsList the list which you want .

List<FriendList> friendList = new Gson().fromJson(httpResult, listType);
This cannot work because it expects your whole JSON document to be just an array of FriendList element (by the way, why "FriendList"?): [{"Username": "abc"},{"Username": "xyz"}] -- this is what can be parsed by your approach.
The easiest solution to fix this (apart from harder to implement but more efficient streamed reading in order to peel of possible unnecessary properties) is just creating a correct mapping:
final class Wrapper {
#SerializedName("Friends")
final List<Friend> friends = null;
}
final class Friend {
#SerializedName("Username")
final String username = null;
}
Now deserialization is trivial and you don't have to define a type token because Gson has enough information for the type from the Wrapper.friends field:
final Wrapper wrapper = gson.fromJson(response, Wrapper.class);
for ( final Friend friend : wrapper.friends ) {
System.out.println(friend.username);
}
Output:
abc
xyz

Change List<FriendList> friendList = new Gson().fromJson(httpResult, listType);
to
FriendList friends = new Gson().fromJson(httpResult, listType);
List<Friend> friends = friends.list;
Updated FriendList.java as mentioned below
FriendList.java
public class FriendList
{
#SerializedName("Friends")
public List<Friend> list;
}
Friend.java
public class Friend
{
#SerializedName("Username")
private String username;
public String getUsername()
{
return username;
}
public void setUsername(String username)
{
this.username = username;
}
}

How to get JSON Object in another one in android

I have the following JSON and I want to get "temp" and "pressure" in "main" key,
but I don't know how to do that.
this is my JSON :

JSONObject mainJsonObject = yourJsonObject.getJSONObject("main");
float pressure = mainJsonObject.getFloat("pressure");
float tempMin = mainJsonObject.getFloat("temp_min");
float tempMax = mainJsonObject.getFloat("temp_max");

String jsonString = ... //Your json string
JSONObject jsonObject = new JSONObject(jsonString);
JSONObject mainObject = jsonObject.getJSONObject("main");
double temp = mainObject.getDouble("temp");
//And get other fields just like the line above.
You can also use Gson library which makes parsing jsons super easy.
First define your model according to your json:
public class JSON {
public Main main;
//...
public static class Main {
public double temp;
public int pressure;
//...
}
}
Then parse the json string using Gson:
JSON object = new Gson().fromJson(jsonString, JSON.class);
double temp = object.main.temp;

First copy your json model to the JsonUtils to generate your models(classes), Then you can easily use Gson to parse your json and deserialize it in to your classes.
For example you can see this Gson Tutorial

You need to get root JSON object, and then get your nested "main" object.
It would be better if you provide your JSON file. But having tree structure, the code should look somehow like this:
//Doing it inside try/catch block, because it may throw JSONException
try{
//Getting root JSON object
JSONObject rootJSON = new JSONObject(s);
//Getting nested "main" object from root object
JSONObject mainJSON = rootJSON.getJSONObject("main");
//Getting custom String from JSON object, say "temp"
String ourString = ourObject.getString("temp");
//Then you can use it whatever way you want
Log.e("JSONObject", ourString);
//Handling JSONException
} catch(JSONException e) {
e.printStackTrace();
}

How to parse JSON without title object in Android?

I've a json output which returns something like this :
[
{
"title":"facebook",
"description":"social networking website",
"url":"http://www.facebook.com"
},
{
"title":"WoW",
"description":"game",
"url":"http://us.battle.net/wow/"
},
{
"title":"google",
"description":"search engine",
"url":"http://www.google.com"
}
]
I am familiar with parsing json having the title object, but i've no clue about how to parse the above json as it is missing the title object. Can you please provide me with some hints/examples so i can check them and work on parsing the above code?
Note : I've checked a similar example here but it doesn't have a satisfactory solution.

Your JSON is an array of objects.
The whole idea around Gson (and other JSON serialization/deserialization) libraries is that you wind up with your own POJOs in the end.
Here's how to create a POJO that represents the object contained in the array and get a List of them from that JSON:
public class App
{
public static void main( String[] args )
{
String json = "[{\"title\":\"facebook\",\"description\":\"social networking website\"," +
"\"url\":\"http://www.facebook.com\"},{\"title\":\"WoW\",\"description\":\"game\"," +
"\"url\":\"http://us.battle.net/wow/\"},{\"title\":\"google\",\"description\":\"search engine\"," +
"\"url\":\"http://www.google.com\"}]";
// The next 3 lines are all that is required to parse your JSON
// into a List of your POJO
Gson gson = new Gson();
Type type = new TypeToken<List<WebsiteInfo>>(){}.getType();
List<WebsiteInfo> list = gson.fromJson(json, type);
// Show that you have the contents as expected.
for (WebsiteInfo i : list)
{
System.out.println(i.title + " : " + i.description);
}
}
}
// Simple POJO just for demonstration. Normally
// these would be private with getters/setters
class WebsiteInfo
{
String title;
String description;
String url;
}
Output:
facebook : social networking website
WoW : game
google : search engine
Edit to add: Because the JSON is an array of things, the use of the TypeToken is required to get to a List because generics are involved. You could actually do the following without it:
WebsiteInfo[] array = new Gson().fromJson(json, WebsiteInfo[].class);
You now have an array of your WebsiteInfo objects from one line of code. That being said, using a generic Collection or List as demonstrated is far more flexible and generally recommended.
You can read more about this in the Gson users guide

JSONArray jsonArr = new JSONArray(jsonResponse);
for(int i=0;i<jsonArr.length();i++){
JSONObject e = jsonArr.getJSONObject(i);
String title = e.getString("title");
}

use JSONObject.has(String name) to check an key name exist in current json or not for example
JSONArray jsonArray = new JSONArray("json String");
for(int i = 0 ; i < jsonArray.length() ; i++) {
JSONObject jsonobj = jsonArray.getJSONObject(i);
String title ="";
if(jsonobj.has("title")){ // check if title exist in JSONObject
String title = jsonobj.getString("title"); // get title
}
else{
title="default value here";
}
}

JSONArray array = new JSONArray(yourJson);
for(int i = 0 ; i < array.lengh(); i++) {
JSONObject product = (JSONObject) array.get(i);
.....
}

how to be easier to analyse the json

i want to analyse the json just like:
[{"id":"ssq","name":"双色球","term":"2010092","date":"2010-08-12 19:15","numbers":{"normal":"3,13,19,27,28,30","special":"2"},"jackpot":"30000000"},{"id":"3d","name":"3D","term":"2010216","date":"2010-08-12 19:55","numbers":{"normal":"6,8,8"},"jackpot":"-"},{"id":"qlc","name":"七乐彩","term":"2010093","date":"2010-08-11 20:45","numbers":{"normal":"08,09,10,11,16,21,27","special":"26"},"jackpot":"0"},{"id":"dfljy","name":"东方6+1","term":"2010093","date":"2010-08-14 18:30","numbers":{"normal":"4,1,3,9,7,2","special":"羊"},"jackpot":"12866531"},{"id":"swxw","name":"15选5","term":"2010217","date":"2010-08-12 18:45","numbers":{"normal":"1,3,5,13,15"},"jackpot":"5693612"},{"id":"ssl","name":"时时乐","term":"20100811-23","date":"2010-08-12 10:27","numbers":{"normal":"6,7,1"},"jackpot":"-"},{"id":"klsf","name":"快乐十分","term":"201021649","date":"2010-08-11 22:00","numbers":{"normal":"5,11,12,14,20"},"jackpot":"-"},{"id":"klsc","name":"快乐双彩","term":"2010215","date":"2010-08-10 21:25","numbers":{"normal":"12,23,10,15,7,3","special":"11"} ,"jackpot":"198059"}]
i want to gain all of them,but the data is so many,so whether i need to create 8 kinds of class to store the data,so to be easier to use.thanks!

To add to cfei's response, one thing that I've done when processing JSON responses from Flickr, is create a new class particularly for that type of object.
So for yours, just playing it by ear, something like the below:
public class Lottery() {
private JSONObject json;
private String id;
private String name;
private String term;
private String date;
private String norm_numbers;
private String spec_numbers;
private String jackpot;
public Lottery(JSONObject json) {
this.json = json;
}
public void setId()
{
try {
id = json.getString("id");
} catch (JSONException e) {
id = "";
}
}
//additional getters and setters, etc.
}
This way, you can make an array of objects, and access the fields like so:
//...get a JSONObject from the array...
Lottery lottery = new Lottery(json);
Log.v("ID", lottery.id);
Log.v("Name", lottery.name);
and so on.

Do you mean that you want to iterate through each of the eight JSONObjects in this JSONArray? You need to create a JSONArray object with the input string you posed above (let's call it "response", as used below) and then iterate through the array to get each JSONObject it contains. For example:
JSONArray array = new JSONArray(response);
for(int i = 0; i < array.length(); i++) {
JSONObject obj = array.getJSONObject(i);
// do something with obj
// example: to get the id for a particular object, use obj.getString("id")
Log.i("Example", "the id is"+obj.getString("id"));
}