CursorEntityIterator.java revision 15a4d2ffd04dc6c70f2cd17dae12ac6bc14c69ab 
1/*
2 * Copyright (C) 2009 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
17package android.content;
18
19import android.database.Cursor;
20import android.os.RemoteException;
21
22/**
23 * Abstract implementation of EntityIterator that makes it easy to wrap a cursor
24 * that can contain several consecutive rows for an entity.
25 * @hide
26 */
27public abstract class CursorEntityIterator implements EntityIterator {
28    private final Cursor mCursor;
29    private boolean mIsClosed;
30
31    /**
32     * Constructor that makes initializes the cursor such that the iterator points to the
33     * first Entity, if there are any.
34     * @param cursor the cursor that contains the rows that make up the entities
35     */
36    public CursorEntityIterator(Cursor cursor) {
37        mIsClosed = false;
38        mCursor = cursor;
39        mCursor.moveToFirst();
40    }
41
42    /**
43     * Returns the entity that the cursor is currently pointing to. This must take care to advance
44     * the cursor past this entity. This will never be called if the cursor is at the end.
45     * @param cursor the cursor that contains the entity rows
46     * @return the entity that the cursor is currently pointing to
47     * @throws RemoteException if a RemoteException is caught while attempting to build the Entity
48     */
49    public abstract Entity getEntityAndIncrementCursor(Cursor cursor) throws RemoteException;
50
51    /**
52     * Returns whether there are more elements to iterate, i.e. whether the
53     * iterator is positioned in front of an element.
54     *
55     * @return {@code true} if there are more elements, {@code false} otherwise.
56     * @see #next
57     */
58    public final boolean hasNext() throws RemoteException {
59        if (mIsClosed) {
60            throw new IllegalStateException("calling hasNext() when the iterator is closed");
61        }
62
63        return !mCursor.isAfterLast();
64    }
65
66    /**
67     * Returns the next object in the iteration, i.e. returns the element in
68     * front of the iterator and advances the iterator by one position.
69     *
70     * @return the next object.
71     * @throws java.util.NoSuchElementException
72     *             if there are no more elements.
73     * @see #hasNext
74     */
75    public Entity next() throws RemoteException {
76        if (mIsClosed) {
77            throw new IllegalStateException("calling next() when the iterator is closed");
78        }
79        if (!hasNext()) {
80            throw new IllegalStateException("you may only call next() if hasNext() is true");
81        }
82
83        return getEntityAndIncrementCursor(mCursor);
84    }
85
86    public final void reset() throws RemoteException {
87        if (mIsClosed) {
88            throw new IllegalStateException("calling reset() when the iterator is closed");
89        }
90        mCursor.moveToFirst();
91    }
92
93    /**
94     * Indicates that this iterator is no longer needed and that any associated resources
95     * may be released (such as a SQLite cursor).
96     */
97    public final void close() {
98        if (mIsClosed) {
99            throw new IllegalStateException("closing when already closed");
100        }
101        mIsClosed = true;
102        mCursor.close();
103    }
104}
105