Question

I have an app that runs 2 threads in loops. 1st one is updating a graph in 1s interval and the second one is updating another graph at 60s interval. The second task is taking a long time since it is quering some server in the internet 3 times that might not always be available and even if it is it will take up to 5-7s to execute.

What is happening is when I launch the second thread it will pause execution of the first one and that is not what I want, I wish both run concurrently. Here in the Youtube video you can see the results of the app running. http://youtu.be/l7K5zSWzlxI
“thread_updater1s” is running a green graph, large readout, and a timer in the corner so you clearly see it stalls for 11 seconds.

1)First of all why is that happening? how to fix it?

2)I’m aware that I might not launch the threads properly at all. I had hard time understanding how to make something to run in a interval loop in Java and my code worked fine for one graph/tread. Now when I have 2 loops in separate threads I don’t know why they are not executing concurrently.

Here is the code:

public class LoopExampleActivity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    this.requestWindowFeature(Window.FEATURE_NO_TITLE);
    setContentView(R.layout.main);
    thread_updater1s.start();
    thread_updater2.start();
}// end of onCreate

final Runnable r1s = new Runnable() {
    public void run() {
        do_1s_updates(); // those are very quick http calls to the local API server 
    }                    // to get data nessessary for some plot.
                        // They have 1s timeout as well but rarely timeout
};

final Runnable r2 = new Runnable() {
    public void run() {
        do_large_updates(); //This makes 7 long call over the Internet to the slow https
                            //server once every 60s. Has 10s timeout and sometimes takes as much as
                            //7s to execute
        }
};

Thread thread_updater1s = new Thread() {
    @Override
    public void run() {
        try {
            while (true) {
                handler.post(r1s);
                sleep(1000);
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
};

Thread thread_updater2 = new Thread() {
    @Override
    public void run() {
        try {
            while (true) {
                handler2.post(r2);
                sleep(60000);
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
};

}

PS. please be forgiving and informative I only code Java for 15 days so far with absolutely no prior experince or lesson.

Answer 1

You need to make the http requests in the threads (not the posted runnables). Then, when you have the data downloaded, you create a runnable with that data that will update the graph and post that runnable to be executed by the UI thread. Here is an example:

public class LoopExampleActivity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    this.requestWindowFeature(Window.FEATURE_NO_TITLE);
    setContentView(R.layout.main);
    thread_updater1s.start();
    thread_updater2.start();
}// end of onCreate

Thread thread_updater1s = new Thread() {
    @Override
    public void run() {
        try {
            while (true) {
                final Object data = getDataFromServer1();
                handler.post(new Runnable() {
                    @Override
                    public void run() {
                        updateGraph1(data);
                    }
                );
                sleep(1000);
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
};

Thread thread_updater2 = new Thread() {
    @Override
    public void run() {
        try {
            while (true) {
                final Object data = getDataFromServer2();
                handler.post(new Runnable() {
                    @Override
                    public void run() {
                        updateGraph2(data);
                    }
                );
                sleep(60000);
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
};

Obviously, change that final Object data by the appropriate class that represents your data downloaded.