Calling web API and Receive return value in Android

Question

I\'ve googled for that topics and don\'t get any useful information.

I want to use Web API in my android projects, but don\'t know how to call them from android or j

Answer 1

public class JsonWebServiceCall {
// HttpURLConnection method to get JSON data from Webservice
public static String GetJsonString(String mUpdateUrl) {

    String result=null;
    try {

        URL url = new URL(mUpdateUrl);

        HttpURLConnection con = (HttpURLConnection) url.openConnection();
        StringBuilder sb = new StringBuilder();

        con.setAllowUserInteraction(false);
        con.setInstanceFollowRedirects(true);
        // con.setRequestMethod("POST");
        con.connect();
         if (con.getResponseCode() == HttpURLConnection.HTTP_OK) {
        // BufferedReader bufferedReader = new BufferedReader(new
        // InputStreamReader(con.getInputStream()));
        try {
            InputStream in = new BufferedInputStream(con.getInputStream());

            BufferedReader bufferedReader = new BufferedReader(
                    new InputStreamReader(in));

            String json;

            while ((json = bufferedReader.readLine()) != null) {
                System.out.println(mUpdateUrl + "kkkkkkkkk------" + json);
                sb.append(json + "\n");
            }
        } catch (Exception e) {

            e.printStackTrace();

        }
        Log.i("json", "===" + sb.toString().trim());
        result=sb.toString().trim();}
         else{
             result=null;
         }
 return result;
    } catch (Exception e) {
        return null;
    }

}

// HttpURLConnection method to get JSON data from Webservice
public static String PostJsonString(String mUpdateUrl, String webserviceurl) {

    // BufferedReader bufferedReader = null;
    try {

        String urlParameters = mUpdateUrl;
        URL url = new URL(webserviceurl);
        URLConnection conn = url.openConnection();
        StringBuilder sb = new StringBuilder();
        conn.setDoOutput(true);

        OutputStreamWriter writer = new OutputStreamWriter(
                conn.getOutputStream());

        writer.write(urlParameters);
        writer.flush();

        String line;
        BufferedReader reader = new BufferedReader(new InputStreamReader(
                conn.getInputStream()));

        while ((line = reader.readLine()) != null) {
            System.out.println(line);
            sb.append(line + "\n");
        }
        writer.close();
        reader.close();
        return sb.toString().trim();
    } catch (Exception e) {
        return null;
    }

}

Asynchtask..........

public static class AsyncCriticalMessage extends AsyncTask<Void, Void, Void> {

    String result = null;
    CriticalMessageServiceSuccess criticalMessageServiceSuccess = null;

    public AsyncCriticalMessage(CriticalMessageServiceSuccess criticalMessageServiceSuccess) {
        this.criticalMessageServiceSuccess = criticalMessageServiceSuccess;
    }

    @Override
    protected Void doInBackground(Void... params) {
        result = JsonWebServiceCall.GetJsonString(Globals.FORCEUPDATE_MESSAGE_SERVICE_URL);
        return null;
    }

    @Override
    protected void onPostExecute(Void Result) {
        super.onPostExecute(Result);

        criticalMessageServiceSuccess.onSuccess(result);
    }
}
 AsyncCriticalMessage asyncCriticalMessage=new AsyncCriticalMessage(this);
    asyncCriticalMessage.execute();

Answer 2

A simple Async call would do the thing for you.:

MainActivity.java

new YourAsync(){

            protected void onPostExecute(Object[] result) {

                String response = result[1].toString();
                try{
                JSONObject jsonObject=(new JSONObject(jsonResult)).getJSONObject("data"); //Parsing json object named 'data'
                yourTextView.setText(jsonObject.getString("uname")); 
        }.execute(YourURL);

YourAsync.java

public class YourAsync extends AsyncTask<String, Integer, Object[]> {

    @Override
    protected Object[] doInBackground(String... params) {
        // TODO Auto-generated method stub

        HttpClient httpclient = new DefaultHttpClient();
        HttpPost httppost = new HttpPost(params[0].toString());
        Log.d("http client post set","");

        try{
            HttpResponse response = httpclient.execute(httppost);
            Log.d("YourAsync","Executed");
            return new Object[]{response, new BasicResponseHandler().handleResponse(response)};
        }catch(Exception e){
            Log.d("" + e, "");
        }
        return new Object[0];
    }

Answer 3

Since I just want to display the the User ID return from the API, below the solution is work for me.

public class MainActivity extends Activity {

    public static TextView txtUserid;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

                    Button btnUserid = (Button) findViewById(R.id.btnUserid);
        btnUserid.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                new UserNameToId().execute("https://uhunt.onlinejudge.org/api/uname2uid/almaruf");
            }
        });
    }

    protected class UserNameToId extends AsyncTask<String, Void, String> {
        @Override
        public String doInBackground(String... url) {

            try {
                URL Url = new URL(url[0]);
                URLConnection urlConnection = Url.openConnection();
                InputStream inputStream = urlConnection.getInputStream();
                BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
                String str = "";
                str = bufferedReader.readLine();
                return str;
            } catch (Exception e) {
                e.printStackTrace();
            }

            return null;
        }

        @Override
        protected void onPostExecute(String result) {
            super.onPostExecute(result);
            txtUserid = (TextView) findViewById(R.id.txtUserId);
            txtUserid.setText(result);
        }
    }
}

Answer 4

You need AsyncTask to do the networking transmission and receiving using appropriate Connection classes, and finally have it return the value to the main UI thread via onPostExecute(). I am really not sure what is the sticking point that prevents you proceeding normally.