from JSONArray to List

Question

I have a class that implements Serializable...

public class Hop implements Serializable {
    private static final long serialVersionUID = 1L;

    public double d1;           
    public double d2;
    public Date date1;      
    public String string;   
    public Date date2;      
}

What I have is an List of Hops ...

List<Hop> hops = new ArrayList<Hop>();
hops.add(hop1);
hops.add(hop2);

JSONObject json = new JSONObject();
json.put("uniqueArrays", new JSONArray(hops));
String arrayList = json.toString();

then I saved this String in SQLite with many other things ...

When I retrieve this String from DB, I want to convert it to List but I am not succesfull ...

How I to it:

JSONObject json = new JSONObject(arrayList );
JSONArray items = json.optJSONArray("uniqueArrays");

how can I convert JSONArray to List ?

//EDIT This is how they looks like when I retrieve them from DB:

 JSONObject: {"uniqueArrays":["com.myapp.app.Hop@41c18ce8"]}
 JSONArray :["com.myapp.app.Hop@41c18ce8"]

try having a look at this http://stackoverflow.com/questions/17037340/converting-jsonarray-to-arraylist — Andre Perkins, Jul 03 '14 at 17:10

Giru Bhai · Accepted Answer · 2014-07-03T18:13:56.663

1

To get list of objects from jsonArray,first get JSONObject from jsonArray then get class object from that JSONobject. So use below code:

JSONArray items = json.optJSONArray("uniqueArrays");
List<Hop> hopsData = new ArrayList<Hop>();

for (int i=0;i<items.length();i++){ 
    JSONObject jObj = items.getJSONObject(i);
    Hop  objHop = new Hop();
    objHop.d1 =jObj.getDouble("d1");
    objHop.d2 =jObj.getDouble("d2");
    objHop.date1 =Date.parse(jObj.getString("date1"));
    objHop.string =jObj.getString("string");
    objHop.date2 = Date.parse(jObj.getString("date2"));
    hopsData.add(objHop);
}

Edit

Your conversion from Arraylist to jsonarray is wrong.So convert arraylist to jsonarray in this way.

List<Hop> hops = new ArrayList<Hop>();
hops.add(hop1); 
hops.add(hop2);
JSONArray jsonArray = new JSONArray();

for(Hop objHop : hops){
       JSONObject jsonObject= new JSONObject();
       jsonObject.put("d1", objHop.d1);
       jsonObject.put("d2", objHop.d2);
       jsonObject.put("date1", String.valueOf(objHop.date1));
       jsonObject.put("string", objHop.string);
       jsonObject.put("date2", String.valueOf(objHop.date2));
       jsonArray.put(jsonObject);
   }

edited Jul 03 '14 at 18:13

answered Jul 03 '14 at 17:12

Giru Bhai

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I had a similiar code, it drops ClassCastException that String cannont be casted to Hop ... – Matej Špilár Jul 03 '14 at 17:16
i think that your logic is rigth ... I did the tried this too ... but look how my JSON looks after toString method ... is that ok ? – Matej Špilár Jul 03 '14 at 17:32
I knew that ... it seems that something is wrong when I save and retrieve it from DB :) – Matej Špilár Jul 03 '14 at 17:39
@MatejŠpilár So first check is jsonArray getting from DB is correct?then get list of object using my answer,it will solve your issue. – Giru Bhai Jul 03 '14 at 17:46
the problem is addings ... in my code above then I put jsonArray to jsonObject the toString is the same as in the edit ... i dunno why – Matej Špilár Jul 03 '14 at 17:51
there is no construcor like new JSONObject(hop1); ... :X – Matej Špilár Jul 03 '14 at 18:06
w8 few minuts please :) – Matej Špilár Jul 03 '14 at 18:14
After minor adjustments (date written as long to JSON, the entire array wrap to JsonObject and thus save to db etc.) ... but in the end it works perfectly! Thank you very much .... really .... Btw: When now I watch it how you did it and it is totally logical basis for all OOP. I should have thought of that. – Matej Špilár Jul 03 '14 at 18:34

from JSONArray to List

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