package com.wasu.cs.widget.wheelview;

import java.util.LinkedList;
import java.util.List;

import android.database.DataSetObserver;
import android.view.View;
import android.view.ViewGroup;

/**
 * Abstract Wheel adapter.
 */
public abstract class AbstractWheelAdapter implements WheelViewAdapter {
    // Observers
    private List<DataSetObserver> mDatasetObservers;

    @Override
    public View getEmptyItem(View convertView, ViewGroup parent) {
        return null;
    }

    @Override
    public void registerDataSetObserver(DataSetObserver observer) {
        if (mDatasetObservers == null) {
            mDatasetObservers = new LinkedList<DataSetObserver>();
        }
        mDatasetObservers.add(observer);
    }

    @Override
    public void unregisterDataSetObserver(DataSetObserver observer) {
        if (mDatasetObservers != null) {
            mDatasetObservers.remove(observer);
        }
    }
    
    /**
     * Notifies observers about data changing
     */
    protected void notifyDataChangedEvent() {
        if (mDatasetObservers != null) {
            for (DataSetObserver observer : mDatasetObservers) {
                observer.onChanged();
            }
        }
    }
    
    /**
     * Notifies observers about invalidating data
     */
    protected void notifyDataInvalidatedEvent() {
        if (mDatasetObservers != null) {
            for (DataSetObserver observer : mDatasetObservers) {
                observer.onInvalidated();
            }
        }
    }
}