Android Network AsyncTask

Issue

I am trying to create a user and POST the user name and password to the server. The code below runs fine in plain java file, but crashed when run in Android due to

android.os.NetworkOnMainThreadException.

I did some search and was told to use AsyncTask but I don't know how to use AsyncTask, how to execute and passing in parameters. I need to pass in url and account Info both are String.

Below is my code that run in plain java file.

public String sendPost(String accountInfo, String input_url) throws Exception {

    // Establish Connection
    URL url = new URL(input_url);
    HttpURLConnection con = (HttpURLConnection) url.openConnection();
    con.setRequestMethod("POST");
    con.setDoOutput(true);

    // Post account info to server
    DataOutputStream wr = new DataOutputStream(con.getOutputStream());
    wr.writeBytes(accountInfo);
    wr.flush();
    wr.close();

    // Check response code and message
    int responseCode = con.getResponseCode();
    IntputStream is = con.getErrorStream();
    String contentAsString = CovertToString(is, 500);
    JSONObject jObject  = new JSONObject(contentAsString);
    jObject.put("response", responseCode);

    return jObject;
}

Below is my attempt to make it into AsyncTask.

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

    @Override
    protected Void doInBackground(String... params) {
        try {
            // Establish Connection
            URL url = new URL(input_url);
            HttpURLConnection con = (HttpURLConnection) url.openConnection();
            con.setRequestMethod("POST");
            con.setDoOutput(true);

            // Post account info to server
            DataOutputStream wr = new DataOutputStream(con.getOutputStream());
            wr.writeBytes(accountInfo);
            wr.flush();
            wr.close();

            // Check response code and message
            int responseCode = con.getResponseCode();
            IntputStream is = con.getErrorStream();
            String contentAsString = CovertToString(is, 500);
            JSONObject jObject  = new JSONObject(contentAsString);
            jObject.put("response", responseCode);

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

    return null;

    }
}

Don't know how to call the method and pass in parameter, and not sure if I implemented the method correctly.

Appreciate any help in advance, thanks!

Solution

You can do something like this.

class Test extends AsyncTask<String, Void, JSONObject>{

    @Override
    protected JSONObject doInBackground(String... params) {
      JSONObject jObject = null;
        try {
          String accountInfo = params[0];
          String input_url = params[1];
            // Establish Connection
            URL url = new URL(input_url);
            HttpURLConnection con = (HttpURLConnection) url.openConnection();
            con.setRequestMethod("POST");
            con.setDoOutput(true);

            // Post account info to server
            DataOutputStream wr = new DataOutputStream(con.getOutputStream());
            wr.writeBytes(accountInfo);
            wr.flush();
            wr.close();

            // Check response code and message
            int responseCode = con.getResponseCode();
            InputStream is = con.getErrorStream();
            String contentAsString = CovertToString(is, 500);
            jObject = new JSONObject(contentAsString);
            jObject.put("response", responseCode);

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

      return jObject;

    }

    protected void onPostExecute(JSONObject data) {
     // do some things with JSONObject as this runs on UI thread.

  }

}

To invoke the task, call

new Test().execute(accountInfo, input_url);

onPostExecute gets called on the UI thread so you can call your UI operations from there..

See here for more information on AsyncTask.

Answered By - Neo