Question

i hope you can help me with my problem. I have to instantiate an http connection and do a get call to the server.
After this call i have to check periodically if the server sent me some data (the connection must not be closed after the first data received). If it does, then i have to parse this data and pass it to an activity and wait again.

My problem is to understand if i’m doing correctly this thing. Here my code

try {
        URL url = getUrl();
        URLConnection urlConn = url.openConnection();
        HttpURLConnection httpConnection = (HttpURLConnection) urlConn;
        httpConnection.setRequestMethod("GET");
        httpConnection.connect();

        while(true) {
            sleep(5000);
            int responseCode = httpConnection.getResponseCode();

            if(responseCode == HttpURLConnection.HTTP_OK) {
                InputStream inputStream = httpConnection.getInputStream();
                String response = null;

                if(inputStream.available() > 0) {
                    long length = inputStream.available();
                    byte[] bytes = new byte[(int) length];
                    inputStream.read(bytes);
                    response = new String(bytes, "UTF-8");
                }
            }
        }                   
    } catch(Exception e) {
        e.printStackTrace();
    }

getUrl() function gives me the complete url that i have to call.
Then i connect through httpConnection.connect();.

while i’m iterating is the connection already opend and capable of receiving incoming data?

I apologize for my english. Thanks a lot

Francesco

Answer 1

From the official android documentation

Uses of this class follow a pattern:

1. Obtain a new HttpURLConnection by calling URL.openConnection() and
   casting the result to HttpURLConnection.

2. Prepare the request. The
   primary property of a request is its URI. Request headers may also
   include metadata such as credentials, preferred content types, and
   session cookies.

3. Optionally upload a request body. Instances must be
   configured with setDoOutput(true) if they include a request body.
   Transmit data by writing to the stream returned by getOutputStream().

4. Read the response. Response headers typically include metadata such as
   the response body’s content type and length, modified dates and
   session cookies. The response body may be read from the stream
   returned by getInputStream(). If the response has no body, that method
   returns an empty stream.

5. Disconnect. Once the response body has been
   read, the HttpURLConnection should be closed by calling disconnect().
   Disconnecting releases the resources held by a connection so they may
   be closed or reused.

As you see from this quote, if you need to send some data to a host you just need to call setDoOutput(true) and use OutputStream of your connection to send data to the host. In this case you use "POST" request method after you called setDoOutput(true). If you don’t need to send data, but just to connect to the host and retrieve data, you also don’t need to call setRequestMethod("GET"), because it’s default request method.

When you connect to the host, just use InputStream to get data from it.