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 * 27 * <p>Instead, will return a {@link Cursor} with 0 records. 28 */ 29 public abstract class NoNullCursorAsyncQueryHandler extends AsyncQueryHandler { 30 NoNullCursorAsyncQueryHandler(ContentResolver cr)31 public NoNullCursorAsyncQueryHandler(ContentResolver cr) { 32 super(cr); 33 } 34 35 @Override startQuery( int token, Object cookie, Uri uri, String[] projection, String selection, String[] selectionArgs, String orderBy)36 public void startQuery( 37 int token, 38 Object cookie, 39 Uri uri, 40 String[] projection, 41 String selection, 42 String[] selectionArgs, 43 String orderBy) { 44 final CookieWithProjection projectionCookie = new CookieWithProjection(cookie, projection); 45 super.startQuery(token, projectionCookie, uri, projection, selection, selectionArgs, orderBy); 46 } 47 48 @Override onQueryComplete(int token, Object cookie, Cursor cursor)49 protected final void onQueryComplete(int token, Object cookie, Cursor cursor) { 50 CookieWithProjection projectionCookie = (CookieWithProjection) cookie; 51 52 super.onQueryComplete(token, projectionCookie.originalCookie, cursor); 53 54 if (cursor == null) { 55 cursor = new EmptyCursor(projectionCookie.projection); 56 } 57 onNotNullableQueryComplete(token, projectionCookie.originalCookie, cursor); 58 } 59 onNotNullableQueryComplete(int token, Object cookie, Cursor cursor)60 protected abstract void onNotNullableQueryComplete(int token, Object cookie, Cursor cursor); 61 62 /** Class to add projection to an existing cookie. */ 63 private static class CookieWithProjection { 64 65 public final Object originalCookie; 66 public final String[] projection; 67 CookieWithProjection(Object cookie, String[] projection)68 public CookieWithProjection(Object cookie, String[] projection) { 69 this.originalCookie = cookie; 70 this.projection = projection; 71 } 72 } 73 } 74