Asynchronous Pubnub calls block android ui thread

Question

I am trying to get the server time from pubnub with the time method

mPubnub.time(callback);

I suppose it is an asynchronous call then I have a waiting loop just after so I can wait for the result

time = -1;
mPubnub.time(callback);
while(time == -1);

In the call back I have

Callback callback = new Callback() {
    public void successCallback(String channel, Object response) {
        try {
            JSONArray jsonArray = new JSONArray(response.toString());
            time = jsonArray.getLong(0) / 10000;
            return;
        } catch (JSONException e) {
            e.printStackTrace();
        }
        time = 0;
    }

    public void errorCallback(String channel, PubnubError error) {
        Log.wtf("error/" + channel, error.toString());
        time = 0;
    }
};

All these calls are from doInBackground of an AsyncTask . Why is it blocking my ui thread. Also calls to publish are also blocking my UI thread and I only call them from an AsyncTask

Many people say the while loop blocks the UI thread but I don't understand why that loop in an AsyncTask would block the UI thread. It wasn't in the onPostExecute or onProgressExecute . It was in doInBackground and it shouldn't block the UI.

On the other hand removing the loop still blocks the UI thread

mPubnub.time(callback);
mPubnub.publish(channel, message, true, callback);

these simple calls block the UI thread and the application stops responding.

Answer 1

This is blocking your UI thread:

while(time == -1);

Instead of doing that, you should handle the success/failure via the callback. If the pubnub API takes a callback like this, it would appear as though it is already handling doing it on a background thread. Just take the appropriate action inside the callback handlers.

Answer 2

while(time == -1);

This line blocks your UI Thread, because of this pointer will never updated by other thread, it's not a volatile variable. You can use Debug Bottle to detect UI Block codes in your project.