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      1 /*
      2  * Copyright (C) 2013 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 package com.android.dreams.phototable;
     17 
     18 import android.content.Context;
     19 import android.content.SharedPreferences;
     20 import android.database.Cursor;
     21 
     22 /**
     23  * Common implementation for sources that load images from a cursor.
     24  */
     25 public abstract class CursorPhotoSource extends PhotoSource {
     26 
     27     // An invalid cursor position to represent the uninitialized state.
     28     protected static final int UNINITIALIZED = -1;
     29     // An invalid cursor position to represent the error state.
     30     protected static final int INVALID = -2;
     31 
     32     public CursorPhotoSource(Context context, SharedPreferences settings) {
     33         super(context, settings);
     34     }
     35 
     36     public CursorPhotoSource(Context context, SharedPreferences settings, PhotoSource fallback) {
     37       super(context, settings, fallback);
     38     }
     39 
     40     @Override
     41     protected ImageData naturalNext(ImageData current) {
     42         if (current.cursor == null || current.cursor.isClosed()) {
     43             openCursor(current);
     44         }
     45         findPosition(current);
     46         current.cursor.moveToPosition(current.position);
     47         current.cursor.moveToNext();
     48         ImageData data = null;
     49         if (!current.cursor.isAfterLast()) {
     50             data = unpackImageData(current.cursor, null);
     51             data.cursor = current.cursor;
     52             data.position = current.cursor.getPosition();
     53         }
     54         return data;
     55     }
     56 
     57     @Override
     58     protected ImageData naturalPrevious(ImageData current) {
     59         if (current.cursor == null || current.cursor.isClosed()) {
     60             openCursor(current);
     61         }
     62         findPosition(current);
     63         current.cursor.moveToPosition(current.position);
     64         current.cursor.moveToPrevious();
     65         ImageData data = null;
     66         if (!current.cursor.isBeforeFirst()) {
     67             data = unpackImageData(current.cursor, null);
     68             data.cursor = current.cursor;
     69             data.position = current.cursor.getPosition();
     70         }
     71         return data;
     72     }
     73 
     74     @Override
     75     protected void donePaging(ImageData current) {
     76         if (current.cursor != null && !current.cursor.isClosed()) {
     77             current.cursor.close();
     78         }
     79     }
     80 
     81     protected abstract void openCursor(ImageData data);
     82     protected abstract void findPosition(ImageData data);
     83     protected abstract ImageData unpackImageData(Cursor cursor, ImageData data);
     84 }
     85 
     86