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      1 /*
      2  * Copyright (C) 2007 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package android.widget;
     18 
     19 import android.database.DataSetObservable;
     20 import android.database.DataSetObserver;
     21 import android.view.View;
     22 import android.view.ViewGroup;
     23 
     24 /**
     25  * Common base class of common implementation for an {@link Adapter} that can be
     26  * used in both {@link ListView} (by implementing the specialized
     27  * {@link ListAdapter} interface) and {@link Spinner} (by implementing the
     28  * specialized {@link SpinnerAdapter} interface).
     29  */
     30 public abstract class BaseAdapter implements ListAdapter, SpinnerAdapter {
     31     private final DataSetObservable mDataSetObservable = new DataSetObservable();
     32 
     33     public boolean hasStableIds() {
     34         return false;
     35     }
     36 
     37     public void registerDataSetObserver(DataSetObserver observer) {
     38         mDataSetObservable.registerObserver(observer);
     39     }
     40 
     41     public void unregisterDataSetObserver(DataSetObserver observer) {
     42         mDataSetObservable.unregisterObserver(observer);
     43     }
     44 
     45     /**
     46      * Notifies the attached observers that the underlying data has been changed
     47      * and any View reflecting the data set should refresh itself.
     48      */
     49     public void notifyDataSetChanged() {
     50         mDataSetObservable.notifyChanged();
     51     }
     52 
     53     /**
     54      * Notifies the attached observers that the underlying data is no longer valid
     55      * or available. Once invoked this adapter is no longer valid and should
     56      * not report further data set changes.
     57      */
     58     public void notifyDataSetInvalidated() {
     59         mDataSetObservable.notifyInvalidated();
     60     }
     61 
     62     public boolean areAllItemsEnabled() {
     63         return true;
     64     }
     65 
     66     public boolean isEnabled(int position) {
     67         return true;
     68     }
     69 
     70     public View getDropDownView(int position, View convertView, ViewGroup parent) {
     71         return getView(position, convertView, parent);
     72     }
     73 
     74     public int getItemViewType(int position) {
     75         return 0;
     76     }
     77 
     78     public int getViewTypeCount() {
     79         return 1;
     80     }
     81 
     82     public boolean isEmpty() {
     83         return getCount() == 0;
     84     }
     85 }
     86