Develop Reference

Android: Convert Json string into List and vice versa

I was looking for an example and alive code to transfer just a list of objects into Json string and vice versa.
It is not a secret, that Androids are often used as a communication devices between (in my case) PC with .NET and the Android device itself.
The very common operation is to send SMS messages to a group of subscribers, that's usually exists as a List of objects.. say..
class Man {
public string Number {get;set;}
public string Message {get;set;}
}
So, the List<Man> Men = new List<Man>();
is quite intuitive as the basic structure.
I can convert both ways in C#.NET
using System;
using Newtonsoft.Json;
using System.Collections.Generic;
public class Program
{
public static void Main() {
List<Man> Men = new List<Man>();
// numbers are just random
Man m1 = new Man();
m1.Number = "+6149168158";
m1.Message = "Hello Bob from 1";
m1.UniqueCode = "0123";
m1.State = 0;
Man m2 = new Man();
m2.Number = "+6146146182";
m2.Message = "Hello Bob from 2";
m2.UniqueCode = "0125";
m2.State = 0;
Men.AddRange(new Man[] { m1, m2 });
string result = JsonConvert.SerializeObject(Men);
Console.WriteLine(result);
List<Man> men = JsonConvert.DeserializeObject<List<Man»(result);
foreach(Man m in men) Console.WriteLine(m.Message);
}
}
public class Man
{
public string Number{get;set;}
public string Message {get;set;}
public string UniqueCode {get;set;}
public int State {get;set;}
}
It works.. but the Android side.. just like a dark matter.. I am sure it exists, but I can't touch it..
So, please, whoever knows it, please, publish the Android part here, so the others would get nice and clear example for such a standard requirement.
(No Gson, Mason or some others.. only Android and only JSON..
Thank you..

It looks like you might not want to use the tools available( Gson, Mason or some others..)
You must manually implement your mapper class for every object:
Native tools for android are JSONArray,JSONObject;
In the following code I have provided an example of decoding
Ok, this is the Deserializator
public List<Man> DecodeFactor(String json) throws JSONException {
List<Man> list = null;
try
{
JSONArray headarrays=new JSONArray(json);
if(headarrays.length()>0)
{
list=new ArrayList<Man>();
for (int i = 0; i <headarrays.length() ; i++)
{
Man man=new Man();
JSONObject o = headarrays.getJSONObject(i);
man.Message = o.getString("Message");
man.Number = o.getString("Number");
man.UniqueCode = o.getString("UniqueCode");
man.State = o.getInt("State");
list.add(man);
}
}
}catch (Exception ee) { ee.printStackTrace(); }
return list;
}

Trouble when searching multiple data from mysql database in android

I am building an app in which I have a view with multiple tabs. Each tab contains a RecyclerView which gets populated from data in MySQL. So there is the Activity with the ViewPager and then each tab has its own Fragment. So I use the Interface to pass data from Fragment to Activity in order to be able to search for. The thing is that if I do not scroll over the tabs the recycler List is null so I cannot search. My question is would it be better if I search directly in the database or is there any other way to do this?
My App looks like this:
The code for passing data is:
Interface:
public interface CoffeeCommunicator {
void sendCoffeeListData(String name, String image, String price);
}
Fragment:
#Override
protected List<ProductList> doInBackground(String... params) {
try {
url = new URL(params[0]);
urlConnection =(HttpURLConnection) url.openConnection();
urlConnection.connect();
urlConnection.setConnectTimeout(5000);
InputStream in = new BufferedInputStream(urlConnection.getInputStream());
jsonResult = StringGenerator.inputStreamToString(in, getActivity());
customList = new ArrayList<>();
jsonResponse = new JSONObject(jsonResult.toString());
jsonMainNode = jsonResponse.optJSONArray(AppConstant.COFFEE_JSON_ARRAY);
for (int i = 0; i < jsonMainNode.length(); i++) {
jsonChildNode = jsonMainNode.getJSONObject(i);
name = jsonChildNode.optString("name");
price = jsonChildNode.optString("price");
image = jsonChildNode.optString("image");
customList.add(new ProductList(image, name, price));
coffeeCommunicator.sendCoffeeListData(name, image, price);
}
} catch (IOException | JSONException e) {
e.printStackTrace();
}
return customList;
}
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
coffeeCommunicator = (CoffeeCommunicator)activity;
}
Activity:
#Override
public void sendCoffeeListData(String name, String image, String price) {
coffeesList.add(new ProductList(image, name, price));
}
So then i have coffeeList available to search for.
Any ideas would be helpfull.

I can give code sample but you know your code better. Here's a sample:
In Activity:
populateList();
coffeeFragment = CoffeeFragment.newInstance();
coffeeFragment.setList(coffeesList);
void populateList() {
jsonResponse = new JSONObject(jsonResult.toString());
jsonMainNode = jsonResponse.optJSONArray(AppConstant.COFFEE_JSON_ARRAY);
for (int i = 0; i < jsonMainNode.length(); i++) {
jsonChildNode = jsonMainNode.getJSONObject(i);
name = jsonChildNode.optString("name");
price = jsonChildNode.optString("price");
image = jsonChildNode.optString("image");
coffeesList.add(new ProductList(image, name, price));
}
}
Fragment:
public void setList(final List<ProductList> arrayList) {
{
customList = arrayList;
}
Note:
Basically you fill data onto coffeesList in Activity. And then pass the List onto the Fragment. I pass a List object by calling a method setList in the Fragment because it is easier.
I hope that is clear enough. Is there a problem with this approach?

It would make sense to query the database when doing an explicit search. That will avoid the problem you're currently having of the data not yet being populated.

If I understand correctly you want to populate data onto RecyclerView. In that case, your method is not the proper way. Here is one Android web page showing data population. Below is a code sample from that web page:
// specify an adapter (see also next example)
mAdapter = new MyAdapter(myDataset);
mRecyclerView.setAdapter(mAdapter);
Notes:
In this code example, myDataset is simply an array of strings; this is the data. It can be any object actually. MyAdapter is a class that you create.
RecyclerView uses the idea of Adapter, like in ListView.
This method populates data immediately after the view is created. It uses virtual caching.
Is this what you had in mind?

Randomize different ArrayList to get a value

I searched for related questions but didn´t find a solution (at least i don´t know if i named it correctly)
So, i have two ArrayLists and i would like to randomize all of them to get a value:
public class ListBox {
public static ArrayList listOne(){
ArrayList<Lists> listOne = new ArrayList<>();
listOne.add(new Item("Text One"));
listOne.add(new Item("Text Two"));
return listOne;
}
public static ArrayList listTwo(){
ArrayList<Lists> listTwo = new ArrayList<>();
listTwo.add(new Item("Text Three"));
listTwo.add(new Item("Text Four"));
return listTwo;
}
}
in other activity:
public void buttonClick(View view){
ArrayList<Lists> algumasListas = ListBox.listOne();
...
}
This is where i shuffle it
public class ListMixer extends ListBox{
public ArrayList<Lists> listas = null;
public ListMixer(ArrayList<Lists> listas ) {
this.listas = listas;
}
protected String mixList(){
Double randomNumber = new Double(Math.random() * listas.size());
int randomNum = randomNumber.intValue();
Lista lista= listas.get(randomNum);
String listaString2 = String.valueOf(lista);
String message = ("This is your list: " + listas);
return message;
}
}
my desired output would be one of the four listItems.
Appreciate the help!

Merge arrays into single one of size N.
Choose a random number in range 0..N-1.
Choose an element by index.

The first bug I'm seeing in your code is that listOne() returns object listTwo when called, which doesn't exist. It probably shouldn't even compile, unless something funky is going on with global scope variables.
The following code should do what you want by merging the two lists into one and then returning a random object from them.
public Object randomFromList(List<Object> listOne, List<Object> listTwo){
List<Object> bigList = new ArrayList<Object>(listOne.size() + listTwo.size());
bigList.addAll(listOne);
bigList.addAll(listTwo);
return bigList.get(new Random().nextInt(bigList.size()));
}
For optimization, if you call this a lot, I would save the Random() object outside of the method to avoid instantiating it every time you make the call.

Parsing JSON then adding multiple strings to an ArrayList

Currently working on an app that takes results from a search, parses the JSON object returned, and then adds the resulting pieces into a few ArrayLists within a class created called VenueList.
Here is the method that receives the results from the service and parses the JSON:
private static List<String> getResultsFromJson(String json) {
ArrayList<String> resultList = new ArrayList<String>();
try {
JSONObject resultsWrapper = (JSONObject) new JSONTokener(json).nextValue();
JSONArray results = resultsWrapper.getJSONArray("results");
for (int i = 0; i < results.length(); i++) {
JSONObject result = results.getJSONObject(i);
resultList.add(result.getString("text"));
}
}
catch (JSONException e) {
Log.e(TAG, "Failed to parse JSON.", e);
}
return resultList;
}
What results of this becomes a List variable call mResults (to clarify: mResults = getResultsFromJson(restResult);. That is then used, among other places, in the following loop that puts the results into an ArrayAdapter that is used for displaying them in a ListFragment:
for (String result : mResults) {
VenueList.addVenue(result, "HELLO WORLD");
adapter.add(result);
}
I also add the result to a class called VenueList that manages the results and makes them accessible for multiple views. It essentially just holds multiple ArrayLists that hold different types of details for each venue returned in the search. The method I use to add a venue to VenueList is below (and you can see it used in the for loop above):
public static void addVenue(String name, String geo) {
venueNames.add(name);
venueGeos.add(geo);
}
I want the addVenue method to be able to take multiple arguments and update the VenueList class. Yet, when I call the addVenue method in the for loop, I can only pass it String result (from the parameters of the loop) and can't figure out how to pass it a second argument (which should also come from the JSON parsed by getResultsFromJson) so I've used "HELLO WORLD" as a placeholder for now.
I realize getResultsFromJson only has one list returned. I need to be able to take multiple elements from the JSON object that I parse, and then add them to VenueList in the right order.
So my questions are:
1) Given the getResultsFromJson method and the for loop, how can I use the addVenue() method as designed? How do I parse multiple elements from the JSON, and then add them to the VenueList at the same time? I plan on adding more arguments to it later on, but I assume if I can make it work with two, I can make it work with four or five.
2) If that's not possible, how should the getResultsFromJson, the for loop, and the addVenue method be redesigned to work properly together?
Please let me know if you need more detail or code - happy to provide. Thank you!
EDIT - Full VenueList class:
public class VenueList {
private static ArrayList<String> venueNames;
private static ArrayList<String> venueGeos;
public VenueList() {
venueNames = new ArrayList<String>();
venueGeos = new ArrayList<String>();
}
public static void addVenue(String name, String geo) {
venueNames.add(name);
venueGeos.add(geo);
}
public static String getVenueName(int position) {
return venueNames.get(position);
}
public static String getVenueGeo(int position) {
return venueGeos.get(position);
}
public static void clearList() {
venueNames.clear();
venueGeos.clear();
}
}
Clarification: I will have additional ArrayLists for each element of data that I want to store about a venue (phone number, address, etc etc)

1) I don't think methods getResultsFromJson(String json) and addVenue(String name, String geo) fit your needs.
2) I would consider rewriting method getResultsFromJson(String json) to something like this:
private static SortedMap<Integer, List<String>> getResultsFromJson(String json) {
Map<Integer, String> resultMap = new TreeMap<Integer, String>();
//...
return resultMap;
}
where the number of keys of your map should be equal to the number of objects you're extracting info, and each one of them will properly have their own list of items just in the right order you extract them.
With this approach you can certainly change your logic to something like this:
// grab your retuned map and get an entrySet, the just iterate trough it
SortedMap<Integer, String> result = returnedMap.entrySet();
for (Entry<Integer, String> result : entrySet) {
Integer key = result.getKey(); // use it if you need it
List<String> yourDesiredItems = result.getValue(); // explicitly shown to know how to get it
VenueList.addVenue(yourDesiredItems);
}
public static void addVenue(List<String> yourDesiredItems) {
// refactor here to iterate the items trough the list and save properly
//....
}
EDIT -- as you wish to avoid the go-between map i'm assuming you need nothing to return from the method
First i'm providing you with a solution to your requirements, then i'll provide you with some tips cause i see some things that could smplify your design.
To save VenueList things directly from getResultsFromJSON do something like this:
private static void getResultsFromJson(String json) {
try {
JSONObject resultsWrapper = (JSONObject) new JSONTokener(json).nextValue();
JSONArray results = resultsWrapper.getJSONArray("results");
for (int i = 0; i < results.length(); i++) {
JSONObject result = results.getJSONObject(i);
//FOR EXAMPLE HERE IS WHERE YOU NEED TO EXTRACT INFO
String name = result.getString("name");
String geo = result.getString("geo");
// and then...
VenueList.addVenue(name, geo, ..., etc);
}
} catch (JSONException e) {
Log.e(TAG, "Failed to parse JSON.", e);
}
}
This implies that your addVenue method should know receive all params needed; as you can see this is just a way (that you can consider a workaround to your needs), however as i don't know all requirements that lead you to code this model, i will point to a few things you might consider:
1. If there's a reason for VenueList class to use everything static, consider doing this:
static{
venueNames = new ArrayList<String>();
venueGeos = new ArrayList<String>();
//....
}
private VenueList(){
}
This way you won't need to get an instance every time and also will avoid null pointer exceptions when doing VenueList.addVenue(...) without previous instantiation.
2. Instead of having an ArrayList for every characteristic in VenueList class consider defining a model object for a Venue like this:
public class Venue{
String name;
String geo;
//... etc
public Venue(){
}
// ... getters & setters
}
then if you need that VenueList class you will just have a list o Venue objects (List<Venue>), this means that instead of calling the method addVenue, you will first create a brand new instance of Venue class and will call the setter method of each characteristic, as an example of the refactored for loop from the workaround i provided you you'd be using something like this:
List<Venue> myListOfVenues = new ArrayList<Venue>();
for (int i = 0; i < results.length(); i++) {
JSONObject result = results.getJSONObject(i);
// THIS WOULD REMAIN THE SAME TO EXTRACT INFO
String name = result.getString("name");
String geo = result.getString("geo");
// and then instead of calling VenueList.addVenue(name, geo, ..., etc)...
Venue v = new Venue();
v.setName(name);
v.setGeo(geo);
// ...etc
myListOfVenues.add(v);
}
// Once you're done, set that List to VenueList class
VenueList.setVenueList(myListOfVenues);
So VenueList class would now have a single property List<Venue> venueList; and would suffer minor tweeks on methods getVenueName, etc... and everything would be more readable... i hope this helps you to get another approach to solve your problem, if i still don't make my point let me know and i'll try to help you out...

Pulling data from a remote mySQL database, using AsyncTask; only displaying very last table row

As the title says really. I have two columns. I want to put them into textviews so I did it. However only the bottom two results, one from each column gets shown. Very odd. Here is my code: http://pastebin.com/qNgfHfT3
The parsing/onPostExecute is towards the bottom where the issue is.
One thing to note: The logs labeled "work" & "dontwork" show all my results, however the logs in the onPostExecute (Google & Google1) only show the last result so I presume the error is in the transfer from parsing to displaying.
Would really appreciate any help here. Thanks.

If you are receiving a JSON response I'd suggest you to parse it by using Gson. It's strongly recommendable as long as you can parse the whole thing in a pair of lines.
Note that creating a proper object it is as easy as doing the following:
YourObject object = gson.fromJson(responseReader, YourObject.class);
or even if you are retrieving a list of items:
Type listType = new TypeToken<List<YourObject>>() {}.getType();
List<YourObject> objects = gson.fromJson(responseReader, listType);
Here's an example that fits exactly your needs
After the process is done you'll have your object (or list of objects) available in an accesible variable.
EDIT:
First your Asynctask should have the following params:
public class HttpTask extends AsyncTask<Void, Void, ArrayList<Driver>> {
and your doInBackground method will need to pass that array to your onPostExecute:
#Override
protected ArrayList<Driver> doInBackground(Void... params) {
For the rest, I take it when the JSon parsing starts.
//PARSING JSON DATA
try {
JSONObject json_data;
Driver d;
jArray = new JSONArray(result);
int l = jArray.length();
if(l>0){
ArrayList<Driver> drivers = newArrayListList<Driver>();
for (int i = 0; i < l; i++) {
json_data = jArray.getJSONObject(i);
d = new Driver(json_data.optString("Driver_full_name"), json_data.optString("Drives_for"));
drivers.add(d);
Log.i("work", returnString);
Log.i("dontwork", somethingelse);
}
} catch (JSONException e1) {
Log.d("DB", "Error somewhere");
CurrentSeasonDrivers_DriverName.this.runOnUiThread(new Runnable() {
public void run() {
Toast.makeText(CurrentSeasonDrivers_DriversName, "Could not parse data so shut up", Toast.LENGTH_LONG).show();
}
});
}
return drivers;
}
protected void onPostExecute(ArrayList<Drivers>... drivers) {
Log.i("Google", returnString);
Log.i("Google1", somethingelse);
String firstDriverName = drivers.get(0).name;
String firstDriverDrivesFor = drivers.get(0).drivesfor;
String secondDriverName = drivers.get(1).name;
TextView drivername = (TextView) findViewById(R.id.DriverName);
drivername.setText(firstDriverName);
TextView drivesfor = (TextView) findViewById(R.id.DrivesFor);
drivesfor.setText(firstDriverDrivesFor);
}
With this and an object for your driver will complete the circle.
public class Driver{
public String name;
public String drivesfor;
public Driver(String _name, String _drivesfor){
name = _name;
drivesfor = _drivesfor;
}
}
I guess you can take over from here.
Let me know about your progress.