Threading in Android

Question

I am currently developing Android app, it needs download content from internet. I use thread to do that and then call runOnUiThread method to update GUI.

1. I placed a refresh menu on it, if user tried to refresh the content, the download thread will be created and started. The problem is that how can I control the thread order, I need to accept the latest request's response and abandon previous thread requests if there were some other requests still running because the request parameters may have been changed by user. Currently I was using a threadId to do this thing, when a thread finished, it will check its threadId, if it was the latest recored one, it then takes control and render the response. My question is that is there any other proper better solution for this?
2. Do I need to stop threads when user exit the app? I remember that some book said that do not try stop thread manually and wait itself finish is a good practice, is that true? Should I stop them by calling "stop" or "interrupt" method?
3. I read some documents around threading in Android and found the class HandlerThread, what is it? In what kind of situation I need to use it?

Answer 1

Rather than starting a new thread for every refresh action I would create a single thread for all the background download work that loops and downloads content as lined up in a queue. That ensures that you don't download content concurrently and also saves resources.

In the GUI you simply queue a refresh request whenever the user prompts you to and can abort a running download by calling HttpRequestBase.abort on the http method instance. The background thread should receive and catch a SocketException and move on to the next queued request.

To end the background thread you just have to end its loop. You can use the Looper and Handler classes to help you with all of the above, the HandlerThread class you mentioned is simply a handy class to create a thread that has a Looper.

The problem with interrupting a thread is that it won't break you out of a blocking I/O request and handling an InterruptException correctly can be complicated. So depending on the situation I would say yes, it is better practice to end the thread by returning from its run method.

Answer 2

i discover this week AsyncTask, and i replace Thread by AsyncTask in some place in my program,
You have doc & sample here, really easy to use :
http://developer.android.com/reference/android/os/AsyncTask.html
when i was using thread GUI was lock, and now it's not locked.
And it's possible to cancel a AsyncTask (but i never try)