A first look into Android Thread

I have started looking into Android. Late to join the show? well, may be, but surely its pretty exciting.

I have tried to build a utility class that can do Network I/O. And grasping things was little hard at first. Network I/O or other heavy-duty stuff in Android should be done on other worker thread. Because doing it in main thread (or the UI thread) can ( and will ) make your application unresponsive and may be killed as the system is persuaded to think that it has hung. For every Android developer, this is a must-read.

So you have to do the long running operations in separate thread. And to interact between threads you have to resort to Handler. A Handler is used to send message or runnable to a particular thread. The thing to remember is that a Handler is associated with the MessageQueue of the single thread which has created it. After creating a Handler, it can be used to post message or runnable to that particular thread.

Here is an example

---

public class MyActivity extends Activity {  

   void startHeavyDutyStuff() {

      // Here is the heavy-duty thread
      Thread t = new Thread() {

          public void run() {
              while (true) {

                  mResults = doSomethingExpensive();

                  //Send update to the main thread
                  messageHandler.sendMessage(Message.obtain(messageHandler, mResults)); 
              }

          }
      };
      t.start();
  }

  // Instantiating the Handler associated with the main thread.
  private Handler messageHandler = new Handler() {

      @Override
      public void handleMessage(Message msg) {  
          switch(msg.what) {
              //handle update
              //.....
          }
      }

  };
}

---

So what is done here? Very simple. A Handler has been created which is bound to the message queue of the main thread. And by using the handler, from the heavy-duty, worker thread we send message to the main thread to be processed.

Feeling like drinking from hose-pipe? Dont worry, I'll post more realistic example soon.