Chiao Cheng | edf7ab9 | 2012-09-14 12:00:21 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2012 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 com.android.contacts.common.database; |
| 18 | |
| 19 | import android.content.AsyncQueryHandler; |
| 20 | import android.content.ContentResolver; |
| 21 | import android.database.Cursor; |
| 22 | import android.net.Uri; |
| 23 | |
| 24 | /** |
| 25 | * An {@AsyncQueryHandler} that will never return a null cursor. |
| 26 | * <p> |
| 27 | * Instead, will return a {@link Cursor} with 0 records. |
| 28 | */ |
| 29 | public abstract class NoNullCursorAsyncQueryHandler extends AsyncQueryHandler { |
| 30 | |
| 31 | public NoNullCursorAsyncQueryHandler(ContentResolver cr) { |
| 32 | super(cr); |
| 33 | } |
| 34 | |
| 35 | @Override |
| 36 | public void startQuery(int token, Object cookie, Uri uri, String[] projection, String selection, |
| 37 | String[] selectionArgs, String orderBy) { |
| 38 | final CookieWithProjection projectionCookie = new CookieWithProjection(cookie, projection); |
| 39 | super.startQuery(token, projectionCookie, uri, projection, selection, selectionArgs, |
| 40 | orderBy); |
| 41 | } |
| 42 | |
| 43 | @Override |
| 44 | protected final void onQueryComplete(int token, Object cookie, Cursor cursor) { |
| 45 | CookieWithProjection projectionCookie = (CookieWithProjection) cookie; |
| 46 | |
| 47 | super.onQueryComplete(token, projectionCookie.originalCookie, cursor); |
| 48 | |
| 49 | if (cursor == null) { |
| 50 | cursor = new EmptyCursor(projectionCookie.projection); |
| 51 | } |
| 52 | onNotNullableQueryComplete(token, projectionCookie.originalCookie, cursor); |
| 53 | } |
| 54 | |
| 55 | protected abstract void onNotNullableQueryComplete(int token, Object cookie, Cursor cursor); |
| 56 | |
| 57 | /** |
| 58 | * Class to add projection to an existing cookie. |
| 59 | */ |
| 60 | private static class CookieWithProjection { |
| 61 | public final Object originalCookie; |
| 62 | public final String[] projection; |
| 63 | |
| 64 | public CookieWithProjection(Object cookie, String[] projection) { |
| 65 | this.originalCookie = cookie; |
| 66 | this.projection = projection; |
| 67 | } |
| 68 | } |
| 69 | } |