无法将JSONObject转换为JSONArray

Question

I'm trying to convert the JSON data that i get back to an array so I can use the data in a listView.

I got the following code:

JSONObject jsonobject;
jsonobject = JSONFunctions.getJSONfromURL("example/url");

ArrayList<String> list = new ArrayList<String>();
JSONArray jsonArray = (JSONArray)jsonobject;
if (jsonArray != null) {
   //do something with it
}

Note: I don't have any experience with Java.
The method getJSONfromURL returns the JSON of the given URL that works just fine but the error is in JSONArray jsonArray = (JSONArray)jsonobject;

It gives the following error: cannot cast JSONObject to JSONArray I've also tried this: JSONArray jsonArray = (JSONObject)(JSONArray)jsonobject;

I can't figure out what i'm doing wrong.

So how can I cast my jsonobject to a normal array that I can use as data for my listView?

Answer 1

A JSONObject is distinct from a JSONArray . If you try new JSONObject("['test', 'array']") , you will get a JSONException: A JSONObject text must begin with '{' at 1 [character 2 line 1] .

Try whether this works for you:

static JSONArray fromUrl(URL url) throws IOException {
    try (
        InputStream openStream = url.openStream();
        BufferedInputStream bis = new BufferedInputStream(openStream);
        Scanner scanner = new Scanner(bis, StandardCharsets.UTF_8.name());
    ) {
        if (!scanner.useDelimiter("\\A").hasNext()) {
            throw new EOFException("empty response");
        }
        return new JSONArray(scanner.next());
    }
}

Answer 2

JSONObject is like a Map in java. Key-value pair. So, you should iterate like iterating a Map:

Iterator iterator = jsonobject.keys();
JSONArray jsonArray = new JSONArray();

while (iterator.hasNext()){
    String key = (String) iterator.next(); // assuming the key to be a String
    // You can put the key also if you want. But, It does not make any sense to do so.
    jsonArray.put(jsonobject.get(key)); 
}