当试图从JSONArray中检索JSONObject时返回null？

Question

Im trying to do the following:

UserFunctions uf = new UserFunctions();
    JSONArray json = uf.getAllFreebies();
    System.out.println(json + "blah1"); //Here im able to retrieve the whole JSONArray.

try{    
System.out.println("1");
    for (int i = 1; i <json.length(); i++) {
        System.out.println("2");
            jo = json.optJSONObject(i); //Im getting null value here
            System.out.println(jo + "blah2"); //Here im getting null

...}

Im printing out my JSONArray using following lines.

JSONArray json = uf.getAllFreebies();
System.out.println(json + "blah1"); 

Now on the following lines when i tried to retrieve the JSONObject from the JSONArray and tried to print it out,it prints out "null" instead of the JSONObject at the particular index.

jo = json.optJSONObject(i);
System.out.println(jo + "blah2"); 

Can anyone pls tell me what am i doing wrong?I mean how can i get a null for JSONOBject when my JSONArray is not null?

Thank You.

Following is my JSONArray logcat:

05-31 21:02:57.156: I/System.out(318): [["viking","Art","Potrait","Potrait","Good","im giving out potrait 7325697","176 Fiat Ave","Iselin","New Jersey","USA","08830","2012-05-27"],["n00b","Books","Novels","Novels","Good","Im giving out novels 7325697","b9 maa krupa","petlad","Gujarat","India","388450","2012-05-27"],["n00b","Computers","laptop","laptop giveaway","Good","Im giving out laptop if you are interested than pls call on 7325697","B9 Ma  Krupa","Petlad","Gujarat","India","388450","2012-05-27"],["mista","Cameras & Photos","Camera","Camera GiveAway","Very good","im giving out camera .its kodak .pls email me on mista@gmail.com","Mista Lee elm street","seoul","Korea","South Korea","ha8 9sd","2012-05-27"],["panda","Gaming Consoles","XBOX","XBOX 360","Very Good","Im giving out xbox 360.if you are interested please email me on panda@gmail.com","435 Carmen Rd,","Buffalo","New York","USA","14226","2012-05-27"],["viking","Cameras & Photos","Camera","Kodak Camera","Good","Kodak Camera giveaway.Pls call on 732397","","Iselin","New Jersey","USA","08830","2012-05-28"],["viking","Books","Novels","Novel GA","Good","Novel give away.call on 7325697.","","Iselin","New Jersey","USA","08830","2012-05-28"],["viking","Automotive","Car","Car GiveAway","Good","Im giving out car.if you are interested pls call 7323697.","176 Fiat Ave","Iselin","New Jersey","USA","08830","2012-05-29"],["viking","Collectibles","Medallions","Medallion GA","Very Good","Im giving out medallion.if inetrested pls call 732697","176 Fiat Ave,","Iselin","New Jersey","USA","08830","2012-05-29"],["viking","Clothing & Accessories","cloths","cloths giveaway","Good","im giving out cloths if you are interested pls call on 735697","176 Fiat Ave,","Iselin","New jersey","USA","08830","2012-05-29"],["viking","Books","Novel","Novel GA","Good","pls call 735697","435 carmen rd","buffalo","ny","usa","14226","2012-05-29"],["viking","Books","TextBook","CHemistry 101","GOod","pls call 735697","176 fiat ave","iselin","new jersey","usa","08830","2012-05-29"],["mista","Books","Notebook","Notbook","Good","im giving out notebbok if you are interested pls call 48374288423","elm street","seaoul","na","South Korea","jfjafjk","2012-05-29"]]blah1

logcat output when trying to print out JSONOBject at index i

05-31 21:02:57.156: I/System.out(318): nullblah2

Answer 1

The JSON [[...], [...], [...]] does not contain JSON-objects, but it does have some JSON-arrays.

Thus optJSONObject finds a JSON-array (where it expected a JSON-object) and returns null because it is of the incorrect type. ( opt is short for optional .)

Use optJSONArray (note Array and not Object ). Alternatively, use getJSONArray , which will throw a JSONException on failure.

Happy coding.

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Note that JSON keeps a strict distinction between Objects, Arrays, and the various Values. The concept of an Array being a special (sub)kind of Object (in the JSON sense) exists in JavaScript but does not necessarily extend to other JSON implementations. For instance, the JSONArray class has no relationship with the JSONObject class.