Question

I’m trying to create an Android app in Java (using Ubuntu 11.10 with the latest Eclipse, ADT and latest Android SDK).

I have the below thread inside a function of its parent class:

new Thread(new Runnable(){
            public void run(){
                    try{
                        list_items = rtm_instance.update_notes_list(list_items);
                        list_items.add("test");

                    } catch (Exception e) {
                        e.printStackTrace();
                    }
        }
}).start();

list_items and rtm_instance are member variables of the class inside which the thread is written. It seems that list_items inside the thread is a snapshot of list_items in the parent class at the point of start()ing the thread.

Though rtm_instance.update_notes_list returns an updated notes list as expected, the changes made to list_items don’t seem to modify the same variable in the parent class. Modifying list_items does nothing more than modify the said variable’s copy inside the thread.

I want the modification to take place in the parent (UI) thread as well, so that an Android ListAdapter detects those and modifies the corresponding ListView. How do I modify the parent thread variable list_items from the child thread posted above?

Thanks!

Answer 1

You probably want the update to happen on the UI thread. You should post a runnable to the Handler from the UIThread. Alternatively you could call runOnUiThread. To have the list on the parent you could define a method on the parent called updateList(String val) and call this rather than changing the list directly.