Android: downloading text data from network url

reference: http://developer.android.com/training/basics/network-ops/connecting.html

1) create method to download string from url

String downloadURL(String strurl) throws IOException{

InputStream is = null;

   // Only display the first 500 characters of the retrieved

   // web page content.

   int len = 500;

   

   try{

    URL url = new URL(strurl);

    HttpURLConnection conn = (HttpURLConnection)url.openConnection();

    conn.setReadTimeout(10000); // 10 sec

    conn.setConnectTimeout(15000); // 15 sec

    conn.setRequestMethod("GET");

    conn.setDoInput(true); // allows receiving data.

    // starts query

    conn.connect();

    int response = conn.getResponseCode();

    Log.d("connection", "response is " + response);

    is = conn.getInputStream();

   

    InputStreamReader reader = new InputStreamReader(is);

   

    char[] buff = new char[len];

    reader.read(buff);

   

    String result =  new String(buff);

    Log.d("connection", "message is " + result);

    return result;

   }

   finally{

    if(is!=null){

    is.close();

    }

   }

}

2) create class to handle download in background process

// class to handle download
// http://developer.android.com/reference/android/os/AsyncTask.html
// < Params, Progress, Result>
// Params - the type of the parameters sent to the task upon execution.
// Progress - the type of the progress units published during the background computation.
// Result - the type of the result of the background computation.
// so in this case, String is the data type of parameter sent to task, void for type of progress units, string for data type of result

class MyTask extends AsyncTask<String, Void, String>{

@Override
  // "String..." = optional parameter. can be nullable 

protected String doInBackground(String... params) {

// TODO Auto-generated method stub

try{

return downloadURL(params[0]);

}

catch (Exception ex){

Log.d("download", "Error is " + ex.getMessage());

}

return null;

}

@Override

protected void onPostExecute(String result) {

// TODO Auto-generated method stub

super.onPostExecute(result);

Log.d("post-execute", result);

et2.setText(result); // display in EditText

}

}

3) Get connection state and execute the background process

// need to have android.permission.ACCESS_NETWORK_STATE

ConnectivityManager mgr = (ConnectivityManager) this.getSystemService(Context.CONNECTIVITY_SERVICE);

NetworkInfo netInfo = mgr.getActiveNetworkInfo();

if(netInfo != null && netInfo.isConnected()){

new MyTask().execute(url);

}