手把手使用Android自带SQLite数据库（1）—

SQLite是一个软件库，实现了自给自足的、无服务器的、零配置的、事务性的 SQL 数据库引擎。详细介绍参见https://www.runoob.com/sqlite/sqlite-intro.html

本系列的文章介绍如何在Android app开发中使用其自带的数据库SQLite，包括定义并建立数据库，在本项目中对数据进行增删改操作。

本文前提：

a、了解SQL数据库基础知识。

b、新建Android app项目TimeTable，开发环境：Android studio。

一、新建文件

在代码目录下新建一个文件夹data，用于存放数据库操作相关的代码。data目录中新建三个文件：

TimeTablecontract.java —— 用于定义数据库和表。

TimeTableDbHelper.java—— 继承 SQLiteOpenHelper，用于创建和升级数据库和表。

TimeTableProvider.java—— 继承 ContentProvider，用于提供对数据库和表的Uri形式的访问方式。

二、上述三个新增文件的内容及介绍：

1、TimeTablecontract.java ：

public class TimeTableContract {// The "Content authority" is a name for the entire content provider, similar to the// relationship between a domain name and its website.  A convenient string to use for the// content authority is the package name for the app, which is guaranteed to be unique on the// device.public static final String CONTENT_AUTHORITY = "com.xuzhi.jinshu.timetable";// Use CONTENT_AUTHORITY to create the base of all URI's which apps will use to contact// the content provider.public static final Uri BASE_CONTENT_URI = Uri.parse("content://" + CONTENT_AUTHORITY);public static final String PATH_COURSE_INFO = CourseInfo.TABLE_NAME;public static final String PATH_EXECUTING_SCHEDULE = ExecutingSchedule.TABLE_NAME;

    public static final class CourseInfo implements BaseColumns {static final public Uri CONTENT_URI =BASE_CONTENT_URI.buildUpon().appendPath(PATH_COURSE_INFO).build();public static final String CONTENT_TYPE =ContentResolver.CURSOR_DIR_BASE_TYPE + "/" + CONTENT_AUTHORITY + "/" + PATH_COURSE_INFO;public static final String CONTENT_ITEM_TYPE =ContentResolver.CURSOR_ITEM_BASE_TYPE + "/" + CONTENT_AUTHORITY + "/" + PATH_COURSE_INFO;public static final String TABLE_NAME = "CourseInfo";public static final String COLUMN_COURSE_NAME = "courseName";public static final String COLUMN_TEACHER_NAME = "teacherName";public static final String COLUMN_STUDENT_NAME = "studentName";public static final String COLUMN_NUMBER_OF_CLASSES = "numberOfClasses";public static final String COLUMN_START_DATE = "startDate";public static final String COLUMN_COURSE_SCHEDULE = "courseSchedule";public static final String COLUMN_PRICE = "price";public static final String COLUMN_NOTE = "note";public static final String COLUMN_IS_TODAY_START = "isTodayStart";public static Uri buildCourseInfoUri(long id) {return ContentUris.withAppendedId(CONTENT_URI, id);}public static Uri buildCourseInfoUriById(int id) {Log.e("BY ID","ID  = " + id);return CONTENT_URI.buildUpon().appendPath(_ID).appendPath(Integer.toString(id)).build();}public static String getTheSecondPara(Uri uri) {return uri.getPathSegments().get(2);}}

public static final class ExecutingSchedule implements BaseColumns {private final String LOG_TAG = this.getClass().getSimpleName();static final public Uri CONTENT_URI =BASE_CONTENT_URI.buildUpon().appendPath(PATH_EXECUTING_SCHEDULE).build();public static final String CONTENT_TYPE =ContentResolver.CURSOR_DIR_BASE_TYPE + "/" + CONTENT_AUTHORITY + "/" + PATH_EXECUTING_SCHEDULE;public static final String CONTENT_ITEM_TYPE =ContentResolver.CURSOR_ITEM_BASE_TYPE + "/" + CONTENT_AUTHORITY + "/" + PATH_EXECUTING_SCHEDULE;public static final String TABLE_NAME = "ExecutingSchedule";public static final String COLUMN_COURSE_ID = "courseId";/*COLUMN_ID in courseInfo: ExtendKey*/public static final String COLUMN_SEQUENCE_ID = "sequenceId";public static final String COLUMN_DATE = "date";public static final String COLUMN_WEEKDAY = "weekday";public static final String COLUMN_START_TIME = "start_time";//format hour:minutepublic static final String COLUMN_END_TIME = "end_time";//format hour:minutepublic static final String COLUMN_LEARN_STATUS = "learn_status";//"unLearned" or "unLearned"or "cancel" or "suspend"public static final String COLUMN_LEAVE_STATUS = "leave_status";//"unLearned" or "unLearned"or "cancel" or "suspend"public static final String COLUMN_CHANGE_STATUS = "change_status";//"unLearned" or "unLearned"or "cancel" or "suspend"public static final String COLUMN_NOTE = "note";//leave_by_student  leave_by_teacher change_by_legal_holiday/*调课时保存调课前的数据*/public static final String COLUMN_DATE_BEFORE_CHANGE = "date_before_change";public static final String COLUMN_WEEKDAY_BEFORE_CHANGE = "weekday_before_change";public static final String COLUMN_START_TIME_BEFORE_CHANGE = "start_time_before_change";//format hour:minutepublic static final String COLUMN_END_TIME_BEFORE_CHANGE = "end_time_before_change";//format hour:minutepublic static final String PATH_COURSE_ID = COLUMN_COURSE_ID;public static final String PATH_ID = _ID;public static final String PATH_SEQUENCE_ID = COLUMN_SEQUENCE_ID;public static Uri buildExecutingScheduleUri(long id) {return ContentUris.withAppendedId(CONTENT_URI, id);}public static Uri buildExecutingScheduleUriWithCourseId(long courseId) {return CONTENT_URI.buildUpon().appendPath(PATH_COURSE_ID).appendPath(String.valueOf(courseId)).build();}public static Uri buildExecutingScheduleUriWithId(long id) {return CONTENT_URI.buildUpon().appendPath(PATH_ID).appendPath(String.valueOf(id)).build();}public static String getTheSecondPara(Uri uri) {return uri.getPathSegments().get(2);}public static String getTheThirdPara(Uri uri) {return uri.getPathSegments().get(3);}}

}

各属性定义说明见下表：

属性	说明
CONTENT_AUTHORITY	本数据库的唯一访问标识
BASE_CONTENT_URI	数据库的Uri访问地址
PATH_COURSE_INFO	数据库中表的相对访问路径
CourseInfo	数据库中表的定义
CourseInfo.CONTENT_URI	表的Uri访问地址
CourseInfo.TABLE_NAME	表名称
CourseInfo.COLUMN_xxx	表中各列名称定义

2、TimeTableDbHelper.java

public class TimeTableDbHelper extends SQLiteOpenHelper {private static final int DATABASE_VERSION = 1;static final public String DATABASE_NAME = "TimeTable.db";private static TimeTableDbHelper instance;/*** 单例模式* @param context 传入上下文* @return 返回TimeTableDbHelper 对象*/public static TimeTableDbHelper getInstance(Context context) {if (null == instance) {synchronized (TimeTableDbHelper.class) {if (null == instance) {instance = new TimeTableDbHelper(context);}}}return instance;}public TimeTableDbHelper(Context context) {super(context, DATABASE_NAME, null, DATABASE_VERSION);}@Overridepublic void onCreate(SQLiteDatabase sqLiteDatabase) {// Create a table to hold CourseTable's info.Log.v(LOG_TAG, "TimeTableDbHelper onCreate");final String SQL_CREATE_COURSE_INFO_TABLE = "CREATE TABLE " + CourseInfo.TABLE_NAME + " (" +CourseInfo._ID + " INTEGER PRIMARY KEY NOT NULL, " +CourseInfo.COLUMN_COURSE_NAME + " TEXT    NOT NULL, " +CourseInfo.COLUMN_TEACHER_NAME + " TEXT    NOT NULL, " +CourseInfo.COLUMN_STUDENT_NAME + " TEXT    NOT NULL, " +CourseInfo.COLUMN_START_DATE + " TEXT    NOT NULL, " +CourseInfo.COLUMN_PRICE + " INTEGER    NOT NULL, " +CourseInfo.COLUMN_COURSE_SCHEDULE + " TEXT    NOT NULL, " +CourseInfo.COLUMN_NOTE + " TEXT    NOT NULL, " +CourseInfo.COLUMN_IS_TODAY_START + " TEXT    NOT NULL, " +CourseInfo.COLUMN_NUMBER_OF_CLASSES + " INTEGER    NOT NULL);";

final String SQL_CREATE_EXECUTING_SCHEDULE_TABLE = "CREATE TABLE " + ExecutingSchedule.TABLE_NAME + " (" +ExecutingSchedule._ID + " INTEGER PRIMARY KEY NOT NULL, " +ExecutingSchedule.COLUMN_COURSE_ID + " INTEGER    NOT NULL, " +ExecutingSchedule.COLUMN_SEQUENCE_ID + " INTEGER    NOT NULL, " +ExecutingSchedule.COLUMN_LEARN_STATUS + " TEXT    default('unLearned'), " +ExecutingSchedule.COLUMN_LEAVE_STATUS + " TEXT    default('no_leave'), " +ExecutingSchedule.COLUMN_CHANGE_STATUS + " TEXT    default('no_change'), " +ExecutingSchedule.COLUMN_NOTE + " TEXT    default(' '), " +ExecutingSchedule.COLUMN_DATE + " TEXT    NOT NULL, " +ExecutingSchedule.COLUMN_WEEKDAY + " TEXT    NOT NULL, " +ExecutingSchedule.COLUMN_START_TIME + " TEXT    NOT NULL, " +ExecutingSchedule.COLUMN_END_TIME + " TEXT    NOT NULL, " +ExecutingSchedule.COLUMN_DATE_BEFORE_CHANGE + " TEXT    default('null'), " +ExecutingSchedule.COLUMN_WEEKDAY_BEFORE_CHANGE + " TEXT    default('null'), " +ExecutingSchedule.COLUMN_START_TIME_BEFORE_CHANGE + " TEXT    default('null'), " +ExecutingSchedule.COLUMN_END_TIME_BEFORE_CHANGE + " TEXT    default('null'));";

      sqLiteDatabase.execSQL(SQL_CREATE_COURSE_INFO_TABLE);sqLiteDatabase.execSQL(SQL_CREATE_EXECUTING_SCHEDULE_TABLE);

    }@Overridepublic void onUpgrade(SQLiteDatabase sqLiteDatabase, int oldVersion, int newVersion) {// This database is only a cache for online data, so its upgrade policy is// to simply to discard the data and start over// Note that this only fires if you change the version number for your database.// It does NOT depend on the version number for your application.// If you want to update the schema without wiping data, commenting out the next 2 lines// should be your top priority before modifying this method.sqLiteDatabase.execSQL("DROP TABLE IF EXISTS " + CourseInfo.TABLE_NAME);sqLiteDatabase.execSQL("DROP TABLE IF EXISTS " + ExecutingSchedule.TABLE_NAME);

        Log.e(LOG_TAG,"onUpgrade");onCreate(sqLiteDatabase);}}

SQLiteOpenHelper 是Android提供的一个类，用于SQLite数据库的创建和版本管理。TimeTableDbHelper 作为SQLiteOpenHelper 的继承类，需要关注以下几项。

内容	说明
`getInstance()`	创建或获取TimeTableDbHelper类。
`onCreate()`	当数据库被创建时调用，在这里实现表的创建和初始化。
`onUpgrade()`	当数据库升级时调用，在这里实现表的新增、删除等操作。
`DATABASE_VERSION`	数据库版本，当数据库需要升级时，需要更新此版本号。
`DATABASE_NAME`	数据库名称。

3、TimeTableProvider.java

public class TimeTableProvider extends ContentProvider {private final String LOG_TAG = this.getClass().getSimpleName();// The URI Matcher used by this content provider.private static final UriMatcher sUriMatcher = buildUriMatcher();private com.xuzhi.jinshu.timetable.data.TimeTableDbHelper mOpenHelper;static final int TIME_TABLE_COURSE_INFO = 100;static final int TIME_TABLE_COURSE_INFO_WITH_ID = 101;static{sTimeTableQueryBuilder = new SQLiteQueryBuilder();}static UriMatcher buildUriMatcher() {// I know what you're thinking.  Why create a UriMatcher when you can use regular// expressions instead?  Because you're not crazy, that's why.// All paths added to the UriMatcher have a corresponding code to return when a match is// found.  The code passed into the constructor represents the code to return for the root// URI.  It's common to use NO_MATCH as the code for this case.final UriMatcher matcher = new UriMatcher(UriMatcher.NO_MATCH);final String authority = CONTENT_AUTHORITY;// For each type of URI you want to add, create a corresponding code.matcher.addURI(authority, PATH_COURSE_INFO, TIME_TABLE_COURSE_INFO);matcher.addURI(authority, PATH_COURSE_INFO + "/" + TimeTableContract.CourseInfo._ID +"/*", TIME_TABLE_COURSE_INFO_WITH_ID);        return matcher;}@Overridepublic boolean onCreate() {mOpenHelper = new TimeTableDbHelper(getContext());return true;}@Overridepublic String getType(Uri uri) {// Use the Uri Matcher to determine what kind of URI this is.final int match = sUriMatcher.match(uri);switch (match) {case TIME_TABLE_COURSE_INFO:return TimeTableContract.CourseInfo.CONTENT_TYPE;case TIME_TABLE_COURSE_INFO_WITH_ID:return TimeTableContract.CourseInfo.CONTENT_ITEM_TYPE;default:throw new UnsupportedOperationException("Unknown uri: " + uri);}}/***************************begin CourseInfo*******************************/private Cursor getAllCourseInfo(Uri uri, String[] projection, String sortOrder) {Log.e(LOG_TAG, TimeTableContract.CourseInfo.TABLE_NAME);sTimeTableQueryBuilder.setTables(TimeTableContract.CourseInfo.TABLE_NAME);return sTimeTableQueryBuilder.query(mOpenHelper.getReadableDatabase(),projection,null,null,null,null,sortOrder);}/*********************end CourseInfo***********************************//***************************begin ExecutingSchedule*******************************///ExecutingSchedule.courseId = ?private static final String sExecutingScheduleByCourseId =TimeTableContract.ExecutingSchedule.TABLE_NAME +"." +  TimeTableContract.ExecutingSchedule.COLUMN_COURSE_ID + " = ? ";private Cursor getExecutingScheduleWithCourseId(Uri uri, String[] projection, String sortOrder)
{String courseId = com.xuzhi.jinshu.timetable.data.TimeTableContract.ExecutingSchedule.getTheSecondPara(uri);Log.e(LOG_TAG, TimeTableContract.ExecutingSchedule.TABLE_NAME);sTimeTableQueryBuilder.setTables(TimeTableContract.ExecutingSchedule.TABLE_NAME);return sTimeTableQueryBuilder.query(mOpenHelper.getReadableDatabase(),projection,sExecutingScheduleByCourseId,new String[]{courseId},null,null,sortOrder);}//ExecutingSchedule._id = ? private static final String sExecutingScheduleByIdSelection = TimeTableContract.ExecutingSchedule.TABLE_NAME + "." + TimeTableContract.ExecutingSchedule._ID + " = ? ";
private int DeleteExecutingScheduleById(Uri uri)
{ String id = TimeTableContract.ExecutingSchedule.getTheSecondPara(uri); final SQLiteDatabase db = mOpenHelper.getWritableDatabase(); return db.delete( TimeTableContract.ExecutingSchedule.TABLE_NAME, sExecutingScheduleByIdSelection, new String[]{id});
}private int UpdateExecutingScheduleById(Uri uri, ContentValues values) {String id = TimeTableContract.ExecutingSchedule.getTheSecondPara(uri);final SQLiteDatabase db = mOpenHelper.getWritableDatabase();return db.update(TimeTableContract.ExecutingSchedule.TABLE_NAME, values, sExecutingScheduleByIdSelection,new String[]{id});}/*********************end ExecutingSchedule***********************************/@Overridepublic Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,String sortOrder) {// Here's the switch statement that, given a URI, will determine what kind of request it is,// and query the database accordingly.Cursor retCursor;Log.e(LOG_TAG, "query uri = " + uri.toString());switch (sUriMatcher.match(uri)) {case TIME_TABLE_COURSE_INFO: {retCursor = getAllCourseInfo(uri, projection, sortOrder);break;}case TIME_TABLE_EXECUTING_SCHEDULE_WITH_COURSE_ID: {retCursor = getExecutingScheduleWithCourseId(uri, projection, sortOrder);break;}default:throw new UnsupportedOperationException("Unknown uri: " + uri);}retCursor.setNotificationUri(getContext().getContentResolver(), uri);return retCursor;}@Overridepublic Uri insert(Uri uri, ContentValues values) {final SQLiteDatabase db = mOpenHelper.getWritableDatabase();final int match = sUriMatcher.match(uri);Uri returnUri;Log.e(LOG_TAG, "insert uri = " + uri.toString());switch (match) {case TIME_TABLE_COURSE_INFO: {long _id = db.insert(TimeTableContract.CourseInfo.TABLE_NAME, null, values);if ( _id > 0 )returnUri = TimeTableContract.CourseInfo.buildCourseInfoUri(_id);elsethrow new android.database.SQLException("Failed to insert row into " + uri);break;}case TIME_TABLE_EXECUTING_SCHEDULE: {long _id = db.insert(TimeTableContract.ExecutingSchedule.TABLE_NAME, null, values);if ( _id > 0 )returnUri = TimeTableContract.ExecutingSchedule.buildExecutingScheduleUri(_id);elsethrow new android.database.SQLException("Failed to insert row into " + uri);break;
}default:throw new UnsupportedOperationException("Unknown uri: " + uri);}getContext().getContentResolver().notifyChange(uri, null);return returnUri;}@Overridepublic int delete(Uri uri, String selection, String[] selectionArgs) {final SQLiteDatabase db = mOpenHelper.getWritableDatabase();final int match = sUriMatcher.match(uri);int rowsDeleted;// this makes delete all rows return the number of rows deletedif ( null == selection ) selection = "1";switch (match) {case TIME_TABLE_EXECUTING_SCHEDULE_WITH_ID:rowsDeleted = DeleteExecutingScheduleById(uri);break;default:throw new UnsupportedOperationException("Unknown uri: " + uri);}// Because a null deletes all rowsif (rowsDeleted != 0) {getContext().getContentResolver().notifyChange(uri, null);}return rowsDeleted;}@Overridepublic int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {final SQLiteDatabase db = mOpenHelper.getWritableDatabase();final int match = sUriMatcher.match(uri);int rowsUpdated;switch (match) {case TIME_TABLE_EXECUTING_SCHEDULE_WITH_ID:rowsUpdated = UpdateExecutingScheduleById(uri, values);break;default:throw new UnsupportedOperationException("Unknown uri: " + uri);}if (rowsUpdated != 0) {getContext().getContentResolver().notifyChange(uri, null);}return rowsUpdated;}@Overridepublic int bulkInsert(Uri uri, ContentValues[] values) {final SQLiteDatabase db = mOpenHelper.getWritableDatabase();final int match = sUriMatcher.match(uri);switch (match) {case TIME_TABLE_COURSE_INFO:{db.beginTransaction();int returnCount = 0;try {for (ContentValues value : values) {long _id = db.insert(TimeTableContract.CourseInfo.TABLE_NAME, null, value);if (_id != -1) {returnCount++;}}db.setTransactionSuccessful();} finally {db.endTransaction();}getContext().getContentResolver().notifyChange(uri, null);return returnCount;}case TIME_TABLE_EXECUTING_SCHEDULE:{db.beginTransaction();int returnCount = 0;try {for (ContentValues value : values) {long _id = db.insert(TimeTableContract.ExecutingSchedule.TABLE_NAME, null, value);if (_id != -1) {returnCount++;}}db.setTransactionSuccessful();} finally {db.endTransaction();}getContext().getContentResolver().notifyChange(uri, null);return returnCount;}default:return super.bulkInsert(uri, values);}}// You do not need to call this method. This is a method specifically to assist the testing// framework in running smoothly. You can read more at:// http://developer.android.com/reference/android/content/ContentProvider.html#shutdown()@Override@TargetApi(11)public void shutdown() {mOpenHelper.close();super.shutdown();}
}

ContentProvider是Android的四大组件之一，它的作用是为不同的模块或应用之间数据共享提供统一的接口。ContentProvider通过Uri来标识被访问的数据，通过ContentResolver的增、删、改、查方法实现对共享数据的操作。

TimeTableProvider作为ContentProvider的继承类，它将TimeTable数据库封装起来，提供Uri形式的数据增、删、改操作。本文的数据库访问仅限于本应用内。

TimeTableProvider需了解的内容如下：

内容	说明
`UriMatcher`	将外部应用和模块访问数据时所使用的Uri映射到ContentProvider内部。
`SQLiteQueryBuilder`	帮助实现SQLite数据库查询操作的类
`getType()`	获取数据库查询结果的类型。类型有两种：0或多个结果、1个结果。
insert(),delete(),update(),query()	数据库操作：增删改查
bulkinsert()	数据库操作：批量插入
shutdown()	关闭数据库

三、配置ContentProvider

为了使用ContentProvider，还需要在App的AndroidManifest.xml中配置它。如下：

<applicationandroid:allowBackup="true"android:icon="@mipmap/ic_launcher"android:label="@string/app_name"android:roundIcon="@mipmap/ic_launcher_round"android:supportsRtl="true"android:theme="@style/AppTheme">
    <providerandroid:name=".data.TimeTableProvider"android:authorities="com.aaa.bbb.timetable" /><activity></activity></application>

————————————————————————

Android SQLite数据库操作的核心文件到此就创建完毕了。

下一篇文我们将介绍在App使用这些文件中的方法来操作数据库。

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