這個(gè)類(lèi)只是提供了兩個(gè)字段，一個(gè)是"_id"一個(gè)是"_count"，便于調(diào)用數(shù)據(jù)庫(kù)時(shí)導(dǎo)致拼寫(xiě)錯(cuò)誤，你也可以擴(kuò)展它，或者自定義這么個(gè)，然后直接調(diào)用它的常量名，防止寫(xiě)sql語(yǔ)句時(shí)把列名拼錯(cuò)

/** 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"; }

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