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/*
* Copyright (C) 2012 The Android Open Source Project
*
* 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.android.contacts.common.database;
import android.content.AsyncQueryHandler;
import android.content.ContentResolver;
import android.database.Cursor;
import android.net.Uri;
import android.support.annotation.Nullable;
import android.support.annotation.VisibleForTesting;
import java.util.concurrent.atomic.AtomicInteger;
/**
* An {@AsyncQueryHandler} that will never return a null cursor.
*
* <p>Instead, will return a {@link Cursor} with 0 records.
*/
public abstract class NoNullCursorAsyncQueryHandler extends AsyncQueryHandler {
private static final AtomicInteger pendingQueryCount = new AtomicInteger();
@Nullable private static PendingQueryCountChangedListener pendingQueryCountChangedListener;
public NoNullCursorAsyncQueryHandler(ContentResolver cr) {
super(cr);
}
@Override
public void startQuery(
int token,
Object cookie,
Uri uri,
String[] projection,
String selection,
String[] selectionArgs,
String orderBy) {
pendingQueryCount.getAndIncrement();
if (pendingQueryCountChangedListener != null) {
pendingQueryCountChangedListener.onPendingQueryCountChanged();
}
final CookieWithProjection projectionCookie = new CookieWithProjection(cookie, projection);
super.startQuery(token, projectionCookie, uri, projection, selection, selectionArgs, orderBy);
}
@Override
protected final void onQueryComplete(int token, Object cookie, Cursor cursor) {
CookieWithProjection projectionCookie = (CookieWithProjection) cookie;
super.onQueryComplete(token, projectionCookie.originalCookie, cursor);
if (cursor == null) {
cursor = new EmptyCursor(projectionCookie.projection);
}
onNotNullableQueryComplete(token, projectionCookie.originalCookie, cursor);
pendingQueryCount.getAndDecrement();
if (pendingQueryCountChangedListener != null) {
pendingQueryCountChangedListener.onPendingQueryCountChanged();
}
}
protected abstract void onNotNullableQueryComplete(int token, Object cookie, Cursor cursor);
@VisibleForTesting(otherwise = VisibleForTesting.NONE)
public static void setPendingQueryCountChangedListener(
@Nullable PendingQueryCountChangedListener listener) {
pendingQueryCountChangedListener = listener;
}
@VisibleForTesting(otherwise = VisibleForTesting.NONE)
public static int getPendingQueryCount() {
return pendingQueryCount.get();
}
/** Callback to listen for changes in the number of queries that have not completed. */
public interface PendingQueryCountChangedListener {
void onPendingQueryCountChanged();
}
/** Class to add projection to an existing cookie. */
private static class CookieWithProjection {
public final Object originalCookie;
public final String[] projection;
public CookieWithProjection(Object cookie, String[] projection) {
this.originalCookie = cookie;
this.projection = projection;
}
}
}
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