Android, creating a simple thread that will updated my seconds counter

Create a Handler in your UI thread, then in the worker thread send a message to the handler (Handler.sendMessage(...)).

The message will be processed on your UI thread, so you can update the text widget correctly. Like this:

private Handler myUIHandler = new Handler(){    @Override    public void handleMessage(Message msg)    {        if (msg.what == some_id_you_created)        {            //Update UI here...        }    }};Then in your thread, to send a message to the handler you do this:Message theMessage = myHandler.obtainMessage(some_id_you_created);myUIHandler.sendMessage(theMessage);//Sends the message to the UI handler.

For this kind of thing, it is a waste to use another thread; it is just a waste and makes it so you have to dael with multithreading issues. Instead, just use Handler.sendDelayedMessage():

static final int MSG_DO_IT = 1;static final long TIME_BETWEEN_MESSAGES = 10 * 1000;  // 10 secondsHandler mHandler = new Handler() {    @Override    public void handleMessage(Message msg) {        switch (msg.what) {            case MSG_DO_IT: {                // Update your UI here...                Message newMsg = obtainMessage(MSG_DO_IT);                sendMessageDelayed(newMsg, TIME_BETWEEN_MESSAGES);            } break;        }    }}@Overridevoid onResume() {    super.onResume();    // Start the timer, executing first event immediately.    Message newMsg = mHandler.obtainMessage(MSG_DO_IT);    mHandler.sendMessage(newMsg);}@Overridevoid onPause() {    super.onPause();    // Stop the timer.    mHandler.removeMessages(MSG_DO_IT);}

Note that this implementation will have some drift -- the actual time between messages is TIME_BETWEEN_MESSAGES + (time to dispatch message). If you need something that won't drift, you can do the timing yourself by using Hander.sendMessageAtTime() and incrementing the new time with a constant value each time, starting with an initial time you get with SystemClock.uptimeMillis() in onResume().

There is a great example of a Timer built using AsyncTask and a Handler with the postDelayed method.

You are correct that updating the UI from a background is a no-no.