Android中广播接收器的奇怪问题

我只有这段代码,非常简单。我有一个列表,在onCreate方法中,我向这个列表添加了一些对象,以便在屏幕上显示它们。我有一个广播接收器,当没有互联网连接时,必须启用/禁用列表中的某些元素。

如果应用程序已在此活动的屏幕中丢失连接,则广播接收器工作正常。问题是在进入此活动之前没有连接。在这种情况下,在onresume()中调用oncreate()方法后,接收器被注册,但当我在接收器中调用getlistview()时,它没有任何子级(尽管我已经在oncreate方法中添加到适配器中,但我还没有加载,然后使用任何线程)。

有人能告诉我为什么会这样吗?

public class MyActivity extends ListActivity {
    private List<MyClass> myObjects;

    private final BroadcastReceiver receiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {

            //check if internet connection is available
            boolean networkAvailable = ... ;
            if (!networkAvailable) {
                //No Internet connection: disabled non-cached objects
                List<MyClass> cachedObjects = getCachedObjects();
                for(int i = 0; i<myObjects.size(); i++){
                    MyClass myObject = myObjects.get(i);
                    if (!cachedSurveys.contains(myObject)) {
                        ListView listView = getListView();
                        //The problem is here: listView is empty when there was no connection
                        //before creating the activity so the broadcast receiver was called in a sticky way                     
                        View child = listView.getChildAt(i);
                        child.setEnabled(false);

                    }
                }
            } else {
                // Internet connection: enable all myObjects
                 int size = getListView().getChildCount();
                 for (int i = 0; i < size; i++) {
                    View child = getListView().getChildAt(i);
                    child.setEnabled(true);
                }
            }
        }
     }; 

     @Override
     public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        myObjects = getMyObjects();

        setListAdapter(new ArrayAdapter<MyClass>(this, android.R.layout.simple_list_item_1, myObjects));
        getListView().setTextFilterEnabled(true);   
}

    @Override
    protected void onResume() {
        super.onResume();
        IntentFilter intentFilter = new IntentFilter("android.net.conn.CONNECTIVITY_CHANGE");
        registerReceiver(receiver, intentFilter);
    }

    @Override
    protected void onPause() {
        super.onPause();
        unregisterReceiver(receiver);
    }
}

谢谢