Android: Handling json objects that can be a string or array

Question

Ran into a situation where am not sure how to handle it.

I have json data that comes from a server; for example:(am just posting part of the json, so, yes, the json is valid)

    "wall_id": 889149,
    "poster_image_thumbnail": "http:\/\/www.mface.me\/images\/avatar\/thumb_62441559ddb1dda7513d0f94.jpg",
    "post_type": "profile",
    "post_content": [{
        "text": "",
        "images_count": 1,
        "images": ["https:\/\/fbcdn-sphotos-a-a.akamaihd.net\/hphotos-ak-ash4\/227408_475848819113499_663318592_n.jpg"]
    }]

Created a class to store this json data

public class feedFormat{
    Integer wall_id;
    String poster_image_thumbnail;
    String post_type;
    String post_content;
}

There are times when post_content can be empty or an array as the example above. I have declared post_content as String in feedFormat. This is obviously throwing a cast exception (Converting array to string?).

I was expecting JSONObject to read it as a string and later convert it into an array from there, but does'nt seem to go that way.

How can i dynamically handle a string or an array? if it is an array, i need to break it down.

I am porting this app from IOS to android, there is a "id" object in IOS that can be of any class. I check if the class is a NSSTring or NSArray and take it from there. Here in Java, am not sure how to handle it.

Any suggestions are highly appreciated

I say use Array, and in case of an empty string put an empty array there instead. — Vesper
– Vesper, Commented Oct 5, 2012 at 9:46

Raphaël Titol · Accepted Answer · 2012-10-05 09:53:17Z

1

If your JSON array is empty, it will be like that :

"post_content": []

It will then remain an array, with the particularity of being 0-sized.

Then I suggest you parse directly your JSON array into a appropriate data structure, whatever the size, like an ArrayList> for example. You will then be able to go through all the items of your JSON array, and for each item, add a new HashMap in your arraylist. Every hashmap will contain there pairs of key values.

However, if I understand well your JSON, it seems that it will be always an array of three elements, the third element being itself a array, which size is given bu the attribute images_count. This is not very good, your JSON structure should be :

"post_content": {
    "text": "",
    "images": [
        "https://fbcdn-sphotos-a-a.akamaihd.net/hphotos-ak-ash4/227408_475848819113499_663318592_n.jpg"
    ]
}

Since images is an array, you can easily get its size.

answered Oct 5, 2012 at 9:53

Raphaël Titol

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5 Comments

Veeru Over a year ago

Thanks Raphael But, at this point i cant change the way post_content comes, it will still be "" - i cant change it because it is already being used by my iphone app.

Raphaël Titol Over a year ago

I understand that you can not change it. In this case, I suggest that in your Android app, you first check if postContent is a JSONArray. If so, parse it the way I indicate : Use an arrayList<HashMap>. However, if you are sure that postContent never contains more than 1 element, you can directly store "text" in a String and cast "images_count" to a integer, and then use an ArrayList<String> for every element of the "images" array. Hope this helps !

Veeru Over a year ago

Am sorry for my ignorance, am a little lost here. I have tried to check if the post_content is array with if (currentRecord.get("post_content") instanceof JSONArray) - which shows true when post_content is array, but i cant seem to break down the array, editing my question now

Raphaël Titol Over a year ago

Your array indeed contains one object only. As you can see, the [], which delimit the array,contain one pair or {}, which delimits your object. Your object however contains 3 elements. Using an array which is always of size 1 is not the right way to do it, that's why I mentionned earlier that your JSON should be adapted to a JSON object, containing one String and one JSON Array elements. TO understand well the JSON syntax, I recommand you to have a look at this link : en.wikipedia.org/wiki/JSON#Data_types.2C_syntax_and_example

Veeru Over a year ago

hey Raphael, yeah i figured that out a few minutes ago. That was purely my mistake and thanks for the reply too. i guess i just need a break for my brain; i have been on a coding marathon and i am missing on simple errors.

Vinay S Shenoy · Accepted Answer · 2012-10-05 09:53:29Z

0

JSONObject has functions called has(String key) which checks if there is a mapping for a key and isNull(String key) which checks if a particular key is null. Use these to check the key before reading.

answered Oct 5, 2012 at 9:53

Vinay S Shenoy

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1 Comment

Vinay S Shenoy Over a year ago

Use @raphael-titol 's answer if your post_content is giving an empty array instead of null.

Cyril Maitre · Accepted Answer · 2012-10-05 09:58:04Z

0

public class FeedFormat{
    Integer wall_id;
    String poster_image_thumbnail;
    String post_type;
    JSONArray post_content;
}

feedFormat toto = new feedFormat();
toto.post_content = yourJsonObject.getJsonArray("post_content");

This is the easiest way to do what you want. Another way is to create another class.

public class FeedFormat{
    Integer wall_id;
    String poster_image_thumbnail;
    String post_type;
    ArrayList<PostContent> post_content = new ArrayList<PostContent>();
}

public class PostContent {
    String text;
    Integer imageCount;
    ArrayList<String> images = new ArrayList<String>();
}

With that you can handle each post content into specific object instead of use JSONObject / JSONArray.

answered Oct 5, 2012 at 9:58

Cyril Maitre

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2 Comments

Veeru Over a year ago

Thanks Cyril, will this work if content is empty? I will give it a shot and see.

Cyril Maitre Over a year ago

If content is empty it will work but before use your data (you want to retrieve all post_content's text for example) check if post_content is empty: .lenght() methode for JSONArray or ArrayList do that.

RajaReddy PolamReddy · Accepted Answer · 2012-10-05 09:59:40Z

0

you can check like this jsonobject.has("post_content")

if(jsonobject.has("post_content")) {
   /// read array and do remaining stuff
}else {
  // if not read another strings and put post_content as null.
}

edited Oct 5, 2012 at 9:59

answered Oct 5, 2012 at 9:54

RajaReddy PolamReddy

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Comments

Permita · Accepted Answer · 2012-10-05 10:06:00Z

0

You can use something like this:

String data= "wall_id": 889149,
"poster_image_thumbnail": "http:\/\/www.mface.me\/images\/avatar\/thumb_62441559ddb1dda7513d0f94.jpg",
"post_type": "profile",
"post_content": [{
    "text": "",
    "images_count": 1,
    "images": ["https:\/\/fbcdn-sphotos-a-a.akamaihd.net\/hphotos-ak-ash4\/227408_475848819113499_663318592_n.jpg"]
}]

JSONArray jArray=data.getJSONArray("post_content");
for(int i=0; i<jArray.length(); i++)
{
JSONObject jObj=jArray.getJSONObject(i);
String text=jObj.getString("text");
int images_count=jObj.getInt("images_count");
String images=jObj.getInt("images");
}

answered Oct 5, 2012 at 10:06

Permita

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1 Comment

Veeru Over a year ago

WIll this not raise a class cast exception when post_content is empty?

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