Implementing a regular JSON parser function to AsyncTask

Issue

I'm developing an app that has lots of remote JSON calls to grab data and implement in the app.

Currently, I'm using this function to get JSON data from URL and parser it.

But unfortunately, it freezes the app until the JSON file is downloaded.

Searched on google, and found out AsyncTask can solve this issue.

I just started on android app development. I tried but failed.

Can you guys please help me to implement this function to AsyncTask?

public class JSONParser {

String charset = "UTF-8";
HttpURLConnection conn;
DataOutputStream wr;
StringBuilder result;
URL urlObj;
JSONObject jObj = null;
JSONArray jAry = null;
StringBuilder sbParams;
String paramsString;

public JSONObject makeHttpRequest(String url, String method, HashMap<String, String> params) {

    sbParams = new StringBuilder();
    int i = 0;
    for (String key : params.keySet()) {
        try {
            if (i != 0) {
                sbParams.append("&");
            }
            sbParams.append(key).append("=")
                    .append(URLEncoder.encode(params.get(key), charset));

        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        i++;
    }

    if (method.equals("POST")) {
        try {
            urlObj = new URL(url);
            conn = (HttpURLConnection) urlObj.openConnection();
            conn.setDoOutput(true);
            conn.setRequestMethod("POST");
            conn.setRequestProperty("Accept-Charset", charset);
            conn.setReadTimeout(10000);
            conn.setConnectTimeout(15000);
            conn.connect();
            paramsString = sbParams.toString();
            wr = new DataOutputStream(conn.getOutputStream());
            wr.writeBytes(paramsString);
            wr.flush();
            wr.close();

        } catch (IOException e) {
            e.printStackTrace();
        }
    } else if (method.equals("GET")) {
        if (sbParams.length() != 0) {
            url += "?" + sbParams.toString();
        }

        Log.d("URL",url);
        try {
            urlObj = new URL(url);
            conn = (HttpURLConnection) urlObj.openConnection();
            conn.setDoOutput(false);
            conn.setRequestMethod("GET");
            conn.setRequestProperty("Accept-Charset", charset);
            conn.setConnectTimeout(15000);
            conn.connect();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    try {
        InputStream in = new BufferedInputStream(conn.getInputStream());
        BufferedReader reader = new BufferedReader(new InputStreamReader(in));
        result = new StringBuilder();
        String line;
        while ((line = reader.readLine()) != null) {
            result.append(line);
        }

        Log.d("JSON Parser", "result: " + result.toString());

    } catch (IOException e) {
        e.printStackTrace();
    }

    conn.disconnect();

    try {
        jObj = new JSONObject(result.toString());
    } catch (JSONException e) {
        Log.e("JSON Parser", "Error parsing data " + e.toString());
    }

    return jObj;
}}

Here's how I make the json call:

JSONParser jsonParser = new JSONParser();
JSONObject json = jsonParser.makeHttpRequest("https://url", "GET", parametters);

Solution

If you want to use an AsyncTask to do that, here's a good start:

public class JsonParser extends AsyncTask<Void, Void, JSONObject> {

    public interface ParserListener {
        void onSuccess(JSONObject result);
        void onFailure();
    }

    private ParserListener listener;    
    private HashMap<String, String> params;
    private String method;
    private String url;
    String charset = "UTF-8";
    HttpURLConnection conn;
    DataOutputStream wr;
    StringBuilder result;
    URL urlObj;
    JSONObject jObj = null;
    JSONArray jAry = null;
    StringBuilder sbParams;
    String paramsString;

    public JsonParser(String url, String method, HashMap<String, String> params) {
        this.url = url;
        this.method = method;
        this.params = params;
    }

    public void setListener(ParserListener listener) {
        this.listener = listener;
    }

    @Override
    protected JSONObject doInBackground(Void... voids) {
        sbParams = new StringBuilder();
        int i = 0;
        for (String key : params.keySet()) {
            try {
                if (i != 0) {
                    sbParams.append("&");
                }
                sbParams.append(key).append("=")
                        .append(URLEncoder.encode(params.get(key), charset));

            } catch (UnsupportedEncodingException e) {
                e.printStackTrace();
            }
            i++;
        }

        if (method.equals("POST")) {
            try {
                urlObj = new URL(url);
                conn = (HttpURLConnection) urlObj.openConnection();
                conn.setDoOutput(true);
                conn.setRequestMethod("POST");
                conn.setRequestProperty("Accept-Charset", charset);
                conn.setReadTimeout(10000);
                conn.setConnectTimeout(15000);
                conn.connect();
                paramsString = sbParams.toString();
                wr = new DataOutputStream(conn.getOutputStream());
                wr.writeBytes(paramsString);
                wr.flush();
                wr.close();

            } catch (IOException e) {
                e.printStackTrace();
            }
        } else if (method.equals("GET")) {
            if (sbParams.length() != 0) {
                url += "?" + sbParams.toString();
            }

            Log.d("URL",url);
            try {
                urlObj = new URL(url);
                conn = (HttpURLConnection) urlObj.openConnection();
                conn.setDoOutput(false);
                conn.setRequestMethod("GET");
                conn.setRequestProperty("Accept-Charset", charset);
                conn.setConnectTimeout(15000);
                conn.connect();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        try {
            InputStream in = new BufferedInputStream(conn.getInputStream());
            BufferedReader reader = new BufferedReader(new InputStreamReader(in));
            result = new StringBuilder();
            String line;
            while ((line = reader.readLine()) != null) {
                result.append(line);
            }

            Log.d("JSON Parser", "result: " + result.toString());

        } catch (IOException e) {
            e.printStackTrace();
        }

        conn.disconnect();

        try {
            jObj = new JSONObject(result.toString());
        } catch (JSONException e) {
            Log.e("JSON Parser", "Error parsing data " + e.toString());
        }

        return jObj;
    }

    @Override
    protected void onPostExecute(JSONObject jsonObject) {
        /* executed on main thread */
        if (listener != null) {
            if (jsonObject != null) {
                listener.onSuccess(jsonObject);
            } else {
                listener.onFailure();
            }
        }
    }
}

and to use it:

JsonParser parser = new JsonParser("https://url", "GET", parameters);
parser.setListener(new JsonParser.ParserListener() {
      @Override
       public void onSuccess(JSONObject result) {
            /* delivered result */
        }

        @Override
        public void onFailure() {
                /* delivered failure */
        }
        });
parser.execute();

Code can be improved and, as pointed out in the comments, there are better approaches to do that. AsyncTask still can be interesting during the learning phase.

Answered By - Lino