用GregorianCalendar日期对象填充ArrayList

Question

I am trying to populate an ArrayList with a GregorianCalendar object so that i can further attach it to a listview adapter. The snapshot shown here is what i want to achieve.....i want the list of date object to be the group listview so that it can compared against events the fall under a particular day (ie events will be the child listview). So far i have written some code but it doesn't populate the arraylist with dates like in the snapshot , instead it adds only the current date (ie only one element). Thanks in advance.

Here is my code

public class EventFragment extends Fragment{

List<GregorianCalendar> dates = new ArrayList<GregorianCalendar>();
List<Events> events = new ArrayList<Events>();

SimpleDateFormat dateFormat;
GregorianCalendar calendar_date;

public EventFragment(){ }


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.fragment_events, container, false);
    return rootView;
}

@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
    listView = (ListView) getView().findViewById(R.id.list);

    dateFormat =  new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    calendar_date = new GregorianCalendar();
    dates.add(calendar_date);

    for(int i = 0; i < dates.size(); i++){
        Log.e("Date", ""+calendar_date.get(i));
    }       
}
}

Answer 1

This is actually more complicated than I think you realise. It's not difficult but will take more code.

I can give a simple example of generating a range of dates as follows. To keep things simple I'll just do one month - January 2015, for example...

Calendar startDate = new GregorianCalendar();

// Set the start date to 1st Jan 2015 and time to 00:00:00 using
// set(int year, int month, int day, int hourOfDay, int minute, int second)
// NOTE: the month field is in the range 0-11 with January being 0
startDate.set(2015, 0, 1, 0, 0, 0);

// Clone the start date and add one month to set the end date to
// 1st February 2015 00:00:00
Calendar endDate = startDate.clone();
endDate.add(Calendar.MONTH, 1); // This adds 1 month

// Step through each day from startDate to endDate (not including endDate itself)
while (startDate.before(endDate)) {

    // Do whatever you need to do here to get the date string from startDate
    // using SimpleDateFormat for example. For logging purposes you can
    // use the next line...
    Log.e("Date", startDate.toString());

    // Now increment the day as follows...
    startDate.add(Calendar.DAY_OF_MONTH, 1);
}

You'll need to do a lot more work when it comes to saving event data and I'd suggest using a SQLite DB. I'd then suggest you change your dates list to simply hold the formatted date strings instead of instances of GregorianCalendar.

List<String> dates = new ArrayList<String>();