CursorHelper.java

/*
 * Copyright (C) 2016 Google Inc. All Rights Reserved.
 *
 * 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 com.google.android.apps.santatracker.data;

import android.database.Cursor;

/**
 * Encapsulates a cursor and provides some handy helper calls.
 */
public abstract class CursorHelper<T> {

    Cursor mCursor;

    CursorHelper(Cursor cursor) {
        mCursor = cursor;
        // reset position of cursor
        mCursor.moveToFirst();
    }

    public boolean isLast() {
        return mCursor.isLast();
    }

    public boolean hasNext() {
        return !mCursor.isAfterLast();
    }

    public boolean isFirst() {
        return mCursor.isFirst();
    }

    /**
     * Returns the current object of the encapsulated cursor.
     */
    public T getCurrent() {
        if (mCursor.isAfterLast()) {
            return null; // at end - no more objects
        } else {
            return getParsedObject();
        }
    }

    /**
     * Returns the next object of the encapsulated cursor without moving
     * it.
     */
    public T getPeekNext() {
        mCursor.moveToNext();
        T object;

        if (mCursor.isAfterLast()) {
            object = null; // at end - no more objects
        } else {
            object = getParsedObject();
        }

        mCursor.moveToPrevious();
        return object;
    }

    /**
     * Moves the cursor to the next position and returns its Object.
     */
    public T getNext() {
        if (mCursor.move(1)) {
            // moved cursor to next position, extract object
            return getParsedObject();
        } else {
            // could not move the cursor, return null as error
            return null;
        }
    }

    public T getPrevious() {
        // verify that there is a previous object
        if (!mCursor.moveToPrevious()) {
            return null;
        }

        T object = getParsedObject();
        mCursor.moveToNext();
        // return previous position
        return object;

    }

    public boolean moveToNext() {
        return mCursor.moveToNext();
    }

    protected abstract T getParsedObject();


}