[android-developers] Re: Socket in AsyncTask - application crashesso the UI won't be blocked

It looks to me that you are trying to do stuff in the UI Thread while
in the doInBackground() function.

You are supposed to do UI related stuff in the onPostExecute(),
onPreExecute() and onProgressUpdate(), not in doInBackground.

This is what I'm talking about:

if (socket.isConnected()) {
OutputStreamOut = new
ObjectOutputStream(socket.getOutputStream());
InputStreamIn = new
ObjectInputStream(socket.getInputStream());
// everything worked fine until here

!!!! This is talking to the UI Thread -> not allowed!!!

statusTxt.setText("App is now
connected to:\n" + IP + " : "
+ Port); // CRASHING !!!!
connectBt.setText("Disconnect");
connected = true;
continueBt.setVisibility(0);
} else {
throw new UnknownHostException();
}

On Jul 19, 11:47 am, Francesco <francescoponti...@gmail.com> wrote:
> Hi, when trying to start a socket connection in an AsyncTask, my
> application crashes for no reason (debugger says
> "android.view.ViewRoot$CalledFromWrongThreadException: Only the
> original thread that created a view hierarchy can touch its views.").
>
> If I remove the Async and use the same code, my application works (of
> course, if I make the socket connect to a not valid IP or port, the
> application freezes for 5 seconds, because that's the socket's
> timeout).
> As I'd like to avoid that 5 seconds freeze with wrong configurations,
> I have to implement the AsyncTask.
>
> The application works just fine opening the socket and everything
> related, but as I try and make it change some TextViews, it gives this
> error. The AsyncTask doc says:
>
> "AsyncTask enables proper and easy use of the UI thread. This class
> allows to perform background operations and publish results on the UI
> thread without having to manipulate threads and/or handlers."
>
> So I'm doing something legit.
>
> This is the code, it's quite simple:
>
>         private class ConnectTask extends AsyncTask<Void, Void, Void> {
>             protected Void doInBackground(Void... params) {
>                 try {
>                         InetAddress inetAddr = InetAddress.getByName(IP);
>                         int PORT = Integer.parseInt(Port);
>
>                                 if (PORT < 0)
>                                         throw (new NumberFormatException());
>                                 if (IP.equals(""))
>                                         throw (new UnknownHostException());
>
>                         SocketAddress sockaddr = new InetSocketAddress(inetAddr,
> PORT);
>                         socket = new Socket();
>                         socket.connect(sockaddr, 5000);
>
>                         if (socket.isConnected()) {
>                                         OutputStreamOut = new
> ObjectOutputStream(socket.getOutputStream());
>                                         InputStreamIn = new ObjectInputStream(socket.getInputStream());
>                         // everything worked fine until here
>                                 statusTxt.setText("App is now connected to:\n" + IP + " : "
> + Port); // CRASHING !!!!
>                                 connectBt.setText("Disconnect");
>                                 connected = true;
>                                 continueBt.setVisibility(0);
>                         } else {
>                                 throw new UnknownHostException();
>                         }
>                 } catch (SocketTimeoutException sockExc) {
>                         statusTxt.setText("Connection timeout:\nplease, review your IP/
> Port settings.");
>                 } catch (NumberFormatException numExc) {
>                         statusTxt.setText("Number Format Error:\nplease, review your
> Port settings.");
>                         } catch (UnknownHostException e1) {
>                                 statusTxt.setText("Unknown Host Error:\nplease, review your IP/
> Port settings.");
>                         } catch (IOException e2) {
>                                 statusTxt.setText("Input/Output Error:\nplease, review your
> connection settings.");
>                         } finally {
>                                 //dialog.dismiss();
>                         }
>             return null;
>             }
>
>             protected void onProgressUpdate(Void... progress) {}
>
>             protected void onPostExecute(Void result) {}
>          }

--
You received this message because you are subscribed to the Google
Groups "Android Developers" group.
To post to this group, send email to android-developers@googlegroups.com
To unsubscribe from this group, send email to
android-developers+unsubscribe@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/android-developers?hl=en