content: /*
   * android-spinnerwheel
   * https://github.com/ai212983/android-spinnerwheel
   *
   * based on
   *
   * Android Wheel Control.
   * https://code.google.com/p/android-wheel/
   *
   * Copyright 2011 Yuri Kanivets
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package antistatic.spinnerwheel.adapters;
  
  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> datasetObservers;
      
      @Override
      public View getEmptyItem(View convertView, ViewGroup parent) {
          return null;
      }
  
      @Override
      public void registerDataSetObserver(DataSetObserver observer) {
          if (datasetObservers == null) {
              datasetObservers = new LinkedList<DataSetObserver>();
          }
          datasetObservers.add(observer);
      }
  
      @Override
      public void unregisterDataSetObserver(DataSetObserver observer) {
          if (datasetObservers != null) {
              datasetObservers.remove(observer);
          }
      }
      
      /**
       * Notifies observers about data changing
       */
      protected void notifyDataChangedEvent() {
          if (datasetObservers != null) {
              for (DataSetObserver observer : datasetObservers) {
                  observer.onChanged();
              }
          }
      }
      
      /**
       * Notifies observers about invalidating data
       */
      protected void notifyDataInvalidatedEvent() {
          if (datasetObservers != null) {
              for (DataSetObserver observer : datasetObservers) {
                  observer.onInvalidated();
              }
          }
      }
  }
  