这个类只是提供了两个字段,一个是"_id"一个是"_count",便于调用数据库时导致拼写错误,你也可以扩展它,或者自定义这么个,然后直接调用它的常量名,防止写sql语句时把列名拼错
/** Copyright (C) 2006 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 android.provider;public interface BaseColumns
{/*** The unique ID for a row.* <P>Type: INTEGER (long)</P>*/public static final String _ID = "_id";/*** The count of rows in a directory.* <P>Type: INTEGER</P>*/public static final String _COUNT = "_count";
}