Android - Runtime error while trying HttpGet on a URL in Android

Question

I'm trying to collect some json data, put those in a string and show them in my app through a toast as for test. I'm pretty sure that the server allows me and responds to my request because previously testing the GET method on Fiddler with the same URL(URI).

Here's the activity/class code:

BufferedReader in = null;
    try {
        HttpClient client = new DefaultHttpClient();
        HttpGet request = new HttpGet();
        try {
            request.setURI(new URI("http://scards.cloudapp.net/api/AddressBooks/3"));
        } catch (URISyntaxException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        HttpResponse response = null;
        try {
            response = client.execute(request);
        } catch (ClientProtocolException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        try {
            in = new BufferedReader
            (new InputStreamReader(response.getEntity().getContent()));
        } catch (IllegalStateException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        StringBuffer sb = new StringBuffer("");
        String line = "";
        String NL = System.getProperty("line.separator");
        try {
            while ((line = in.readLine()) != null) {
                sb.append(line + NL);
            }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        try {
            in.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        String page = sb.toString();
        Toast.makeText(this, page, Toast.LENGTH_LONG).show();

        } finally {
        if (in != null) {
            try {
                in.close();
                } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

And in LogCat it shows me that I have android.os.NetworkOnMainThreadException. Open to suggestions and corrections.

Project properties : SDK: API16 - Android 4.1.2, minBuilSDK : API:7 Android 2.1(Eclair) - Eclipse SDK 4.2

Answer 1

Here is an example of AsyncTask below. Also here is a great tutorial

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

    private ProgressDialog progressDialog = new ProgressDialog(MainActivity.this);
    InputStream inputStream = null;
    String result = ""; 

    protected void onPreExecute() {
        progressDialog.setMessage("Your progress dialog message...");
        progressDialog.show();
        progressDialog.setOnCancelListener(new OnCancelListener() {
            public void onCancel(DialogInterface arg0) {
                MyAsyncTask.this.cancel(true);
            }
        });
    }

    @Override
    protected Void doInBackground(String... params) {

        String url_select = "http://yoururlhere.com";

                ArrayList<NameValuePair> param = new ArrayList<NameValuePair>();

        try {
            // Set up HTTP post
            // HttpClient is more then less deprecated. Need to change to URLConnection
            HttpClient httpClient = new DefaultHttpClient();

            HttpPost httpPost = new HttpPost(url_select);
            httpPost.setEntity(new UrlEncodedFormEntity(param));
            HttpResponse httpResponse = httpClient.execute(httpPost);
            HttpEntity httpEntity = httpResponse.getEntity();

            // Read content & Log
            inputStream = httpEntity.getContent();
        } catch (UnsupportedEncodingException e1) {
            Log.e("UnsupportedEncodingException", e1.toString());
            e1.printStackTrace();
        } catch (ClientProtocolException e2) {
            Log.e("ClientProtocolException", e2.toString());
            e2.printStackTrace();
        } catch (IllegalStateException e3) {
            Log.e("IllegalStateException", e3.toString());
            e3.printStackTrace();
        } catch (IOException e4) {
            Log.e("IOException", e4.toString());
            e4.printStackTrace();
        }
        // Convert response to string using String Builder
        try {
            BufferedReader bReader = new BufferedReader(new InputStreamReader(inputStream, "iso-8859-1"), 8);
            StringBuilder sBuilder = new StringBuilder();

            String line = null;
            while ((line = bReader.readLine()) != null) {
                sBuilder.append(line + "\n");
            }

            inputStream.close();
            result = sBuilder.toString();

        } catch (Exception e) {
            Log.e("StringBuilding & BufferedReader", "Error converting result " + e.toString());
        }
    } // protected Void doInBackground(String... params)


    protected void onPostExecute(Void v) {

        //parse JSON data
        try{
            JSONArray jArray = new JSONArray(result);

            for(int i=0; i < jArray.length(); i++) {

                JSONObject jObject = jArray.getJSONObject(i);

                String name = jObject.getString("name");
                String tab1_text = jObject.getString("tab1_text");
                int active = jObject.getInt("active");


            } // End for Loop

            this.progressDialog.dismiss();

        } catch (JSONException e) {

            Log.e("JSONException", "Error: " + e.toString());

        } // catch (JSONException e)


    } // protected void onPostExecute(Void v)

} //class MyAsyncTask extends AsyncTask<String, String, Void>

---

I call my AsyncTask with this line:

new MyAsyncTask().execute();

---

Here is a Youtube tutorial (from the New Boston) for AsyncTask that I found helpful.

Android Application Development Tutorial - 101 - Async Task class to load stuff
Android Application Development Tutorial - 102 - The 4 AsyncTask Methods
Android Application Development Tutorial - 103 - ProgressDialog and Correction

Answer 2

You should never access network from the main thread. Use AsyncTask class' doInBackground method to access the network.