android app shows blank screen (not updating ui) while in a loop

Question

In my application, a client is connected to server. It waits until the connection to the server occurs. During that time the application is not responding. How can i solve this problem. Tried code snippet shows below

public Connection(){
    client.SetParent(this);
    this.context = g.getContext();
    bConnected = false;

    mNetworkRunner = new Runnable() {
        public void run() {
            try {
                Log.e("", "mNetworkRunner...");

                if( SendKeepAlive()){
                    Main.conStatus(1);
                    Log.e("", "SendKeepAlive...");
                }
                else {
                    Main.conStatus(0);
                    Log.e("", "No connection...");

                    g.log("Connection to server is lost... Trying to Connect...");
                    while(true){
                        Log.e("", "In while loop...");

                        if(!Connect()){
                            g.log("Trying...");
                            Log.e("", "In Connect no connect...");
                            Thread.sleep(2000);
                        }
                        else {
                            g.log("Connected");
                            break;
                        }

                    }
                    Main.conStatus(1);
                }
                mNetworkHandler.postDelayed(this, 30000);
            }
            catch (Exception e) {
                e.printStackTrace();
            }
        }
    };      

}
// 
private void CheckNetworkConnection(){
    if( mNetworkHandler == null ){
        mNetworkHandler = new Handler();
        mNetworkHandler.post(mNetworkRunner);
        Log.e("", "CheckNetworkConnection...");
    }       
}

Answer 1

You are doing a lot of time consuming work in UI Thread, which create problem. In this situation you should use AsyncTask.

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.

 private class DownloadFilesTask extends AsyncTask<URL, Integer, Long> {
     protected Long doInBackground(URL... urls) {

    //do your time consuming task here
     }

     protected void onProgressUpdate(Integer... progress) {
         //setProgressPercent(progress[0]);
     }

     protected void onPostExecute(Long result) {
         //showDialog("Downloaded " + result + " bytes");
     }
 }

Once created, a task is executed very simply:

 new DownloadFilesTask().execute(url1, url2, url3);

Answer 2

mNetworkHandler = new Handler() will make Runnable execute on UI Thread, you need HandlerThread

private void CheckNetworkConnection(){
    if( mNetworkHandler == null ){
        HandlerThread handlerThread = new HandlerThread("thread");
        handlerThread.start();
        mNetworkHandler =  new Handler(handlerThread.getLooper());
        mNetworkHandler.post(mNetworkRunner);
        Log.e("", "CheckNetworkConnection...");
    }
}