Android: read JSON data

Question

I have a url that gives me the data in this format:

{"to": "DKK", "rate": 7.4417, "from": "EUR"}

I’m trying to read them this way:

JSONObject obj = new JSONObject();
JSONObject obj2 = obj.getJSONObject(site);
String to = (String)obj2.get("to");
Double rate = obj2.getDouble("rate");

ERROR:

org.json.Jsonexception: No value for http://rate-exchange-1.appspot.com/currency?from=EUR&to=DKK 04-22 23:06:56.114 19331-19991/com.converter.android.converter W/System.err: at org.json.Jsonobject.get(Jsonobject.java:389) 04-22 23:06:56.114 19331-19991/com.converter.android.converter W/System.err: at org.json.Jsonobject.getJSONObject(Jsonobject.java:609) 04-22 23:06:56.114 19331-19991/com.converter.android.converter W/System.err: at com.converter.android.converter.Convertactivity$Parse.doInBackground(Convertactivity.java:1579) 04-22 23:06:56.114 19331-19991/com.converter.android.converter W/System.err: at com.converter.android.converter.Convertactivity$Parse.doInBackground(Convertactivity.java:1547) 04-22 23:06:56.114 19331-19991/com.converter.android.converter W/System.err: at android.os.Asynctask$2.call(Asynctask.java:295) 04-22 23:06:56.114 19331-19991/com.converter.android.converter W/System.err: at java.util.current.FutureTask.run(Futuretask.java:237) 04-22 23:06:56.114 19331-19991/com.converter.android.converter W/System.err: at android.os.Asynctask$Serialexecutor$1.run(Asynctask.java:234) 04-22 23:06:56.114 19331-19991/com.converter.android.converter W/System.err: at java.util.current.ThreadPoolExecutor.runWorker(Threadpoolexecutor.java:1113) 04-22 23:06:56.114 19331-19991/com.converter.android.converter W/System.err: at java.util.Concurrent.Threadpoolexecutor$Worker.run(Threadpoolexecutor.java:588) 04-22 23:06:56.114 19331-19991/com.converter.android.converter W/System.err: at java.lang.Thread.run(Thread.java:818)

Can someone help me?

Answer 1

You have to pass the answer from the site to json, not the url. To get the answer use this class:

public class HttpConnections {
 //método get
public static String get(String urlString){
    HttpURLConnection urlConnection = null;
    BufferedReader reader = null;
    String resposta = null;
    try {
        URL url = new URL(urlString);
        urlConnection = (HttpURLConnection) url.openConnection();
        urlConnection.connect();

        InputStream in = new BufferedInputStream(urlConnection.getInputStream());

        reader = new BufferedReader(new InputStreamReader(in));
        String line = "";
        StringBuffer buffer = new StringBuffer();
        while ((line = reader.readLine()) != null){
            buffer.append(line);
        }
        resposta = buffer.toString();
    }catch (Exception e){
        e.printStackTrace();
    }finally {
        if (urlConnection != null){
            urlConnection.disconnect();
        }
        try {
            reader.close();
        }catch (Exception e){
            e.printStackTrace();
        }
    }
    return resposta;
}
}

Then just call passing your url(has to be used in another Thread).

String resposta = HttpConnections.get(" http://rate-exchange-1.appspot.com/currency?from=EUR&to=DKK");
JSONObject obj = new JSONObject(resposta);
String to = obj.getString("to");
Double rate = obj.getDouble("rate");
String from = obj.getString("from");

Answer 2

You’re trying to do parse website. However, you should do parse the answer (data) this URL gives you. For example"

JSONObject obj = new JSONObject(resposta);
String to = obj.getString("to");

Note that the Jsonobject object does not get the data from the site. You will have to use some library for this, for example Okhttp