手把手使用Android自帶SQLite數據庫（1）—— 建立核心文件

SQLite是一個軟件庫，實現了自給自足的、無服務器的、零配置的、事務性的 SQL 數據庫引擎。詳細介紹參見https://www.runoob.com/sqlite/sqlite-intro.html

本系列的文章介紹如何在Android app開發中使用其自帶的數據庫SQLite，包括定義並建立數據庫，在本項目中對數據進行增刪改操作。

本文前提：

a、瞭解SQL數據庫基礎知識。

b、新建Android app項目TimeTable，開發環境：Android studio。

一、新建文件

在代碼目錄下新建一個文件夾data，用於存放數據庫操作相關的代碼。data目錄中新建三個文件：

TimeTablecontract.java —— 用於定義數據庫和表。

TimeTableDbHelper.java—— 繼承 SQLiteOpenHelper，用於創建和升級數據庫和表。

TimeTableProvider.java—— 繼承 ContentProvider，用於提供對數據庫和表的Uri形式的訪問方式。

二、上述三個新增文件的內容及介紹：

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:minute
    public static final String COLUMN_END_TIME = "end_time";//format hour:minute
    public 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
    /*調課時保存調課前的數據*/
    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:minute
    public static final String COLUMN_END_TIME_BEFORE_CHANGE = "end_time_before_change";//format hour:minute

    public 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);
    }

}

}

各屬性定義說明見下表：

屬性	說明
CONTENT_AUTHORITY	本數據庫的唯一訪問標識
BASE_CONTENT_URI	數據庫的Uri訪問地址
PATH_COURSE_INFO	數據庫中表的相對訪問路徑
CourseInfo	數據庫中表的定義
CourseInfo.CONTENT_URI	表的Uri訪問地址
CourseInfo.TABLE_NAME	表名稱
CourseInfo.COLUMN_xxx	表中各列名稱定義

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;

    /**
     * 單例模式
     * @param context 傳入上下文
     * @return 返回TimeTableDbHelper 對象
     */
    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);
    }

    @Override
    public 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);

    }

    @Override
    public 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提供的一個類，用於SQLite數據庫的創建和版本管理。TimeTableDbHelper 作爲SQLiteOpenHelper 的繼承類，需要關注以下幾項。

內容	說明
`getInstance()`	創建或獲取TimeTableDbHelper類。
`onCreate()`	當數據庫被創建時調用，在這裏實現表的創建和初始化。
`onUpgrade()`	當數據庫升級時調用，在這裏實現表的新增、刪除等操作。
`DATABASE_VERSION`	數據庫版本，當數據庫需要升級時，需要更新此版本號。
`DATABASE_NAME`	數據庫名稱。

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;
    }
    @Override
    public boolean onCreate() {
        mOpenHelper = new TimeTableDbHelper(getContext());
        return true;
    }
    @Override
    public 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***********************************/

    @Override
    public 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;
    }

    @Override
    public 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);
                else
                    throw 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);
               else
                   throw 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;
    }

    @Override
    public 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 deleted
        if ( 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 rows
        if (rowsDeleted != 0) {
            getContext().getContentResolver().notifyChange(uri, null);
        }
        return rowsDeleted;
    }



    @Override
    public 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;
    }

    @Override
    public 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的四大組件之一，它的作用是爲不同的模塊或應用之間數據共享提供統一的接口。ContentProvider通過Uri來標識被訪問的數據，通過ContentResolver的增、刪、改、查方法實現對共享數據的操作。

TimeTableProvider作爲ContentProvider的繼承類，它將TimeTable數據庫封裝起來，提供Uri形式的數據增、刪、改操作。本文的數據庫訪問僅限於本應用內。

TimeTableProvider需瞭解的內容如下：

內容	說明
`UriMatcher`	將外部應用和模塊訪問數據時所使用的Uri映射到ContentProvider內部。
`SQLiteQueryBuilder`	幫助實現SQLite數據庫查詢操作的類
`getType()`	獲取數據庫查詢結果的類型。類型有兩種：0或多個結果、1個結果。
insert(),delete(),update(),query()	數據庫操作：增刪改查
bulkinsert()	數據庫操作：批量插入
shutdown()	關閉數據庫

三、配置ContentProvider

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

<application
    android: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">
    <provider
        android:name=".data.TimeTableProvider"
        android:authorities="com.aaa.bbb.timetable" />
    <activity></activity></application>

————————————————————————

Android SQLite數據庫操作的核心文件到此就創建完畢了。

下一篇文我們將介紹在App使用這些文件中的方法來操作數據庫。

手把手使用Android自帶SQLite數據庫（1）—— 建立核心文件

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