Android中的SQLite

示例代码：

        MessageDatabaseHelper databaseHelper = new MessageDatabaseHelper(this);        databaseHelper.getWritableDatabase();

public class MessageDatabaseHelper extends SQLiteOpenHelper {    private static final String DB_NAME = "message.db";    private static final int DB_VERSION = 1;    private static class MessageTable {        private static final String TABLE_NAME = "message";        private static final String COLUMN_NAME_ID = "_id";        private static final String COLUMN_NAME_FROM_NAME = "from_name";        private static final String COLUMN_NAME_TO_NAME = "to_name";        private static final String COLUMN_NAME_TIME = "time";        private static final String COLUMN_NAME_CONTENT = "content";        private static final String COLUMN_NAME_STATE = "state";    }    public MessageDatabaseHelper(Context context) {        //数据库文件名，数据库版本号        super(context, DB_NAME, null, DB_VERSION);    }    //创建数据库，调用建表语句    @Override    public void onCreate(SQLiteDatabase db) {        db.execSQL("CREATE TABLE " + MessageTable.TABLE_NAME + " ("                + MessageTable.COLUMN_NAME_ID + " INTEGER PRIMARY KEY,"                + MessageTable.COLUMN_NAME_FROM_NAME + " TEXT,"                + MessageTable.COLUMN_NAME_TO_NAME + " TEXT,"                + MessageTable.COLUMN_NAME_TIME + " INTEGER,"                + MessageTable.COLUMN_NAME_CONTENT + " TEXT,"                + MessageTable.COLUMN_NAME_STATE + " INTEGER"                + ");");    }    //升级数据库，第一个数据库版本不需要写升级语句    @Override    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {    }    //获取只读数据库    @Override    public SQLiteDatabase getReadableDatabase() {        return super.getReadableDatabase();    }    //获取读写数据库    @Override    public SQLiteDatabase getWritableDatabase() {        return super.getWritableDatabase();    }}

插入数据

    //增加数据    public void insertMessage(Message message) {        SQLiteDatabase database = getWritableDatabase();        ContentValues contentValues = new ContentValues();        contentValues.put(MessageTable.COLUMN_NAME_ID, message.getId());        contentValues.put(MessageTable.COLUMN_NAME_FROM_NAME, message.getFromName());        contentValues.put(MessageTable.COLUMN_NAME_TO_NAME, message.getToName());        contentValues.put(MessageTable.COLUMN_NAME_TIME, message.getTime());        contentValues.put(MessageTable.COLUMN_NAME_CONTENT, message.getContent());        contentValues.put(MessageTable.COLUMN_NAME_STATE, message.getState());        database.insertWithOnConflict(                MessageTable.TABLE_NAME,                null,                contentValues,                SQLiteDatabase.CONFLICT_REPLACE);    }

删除数据

    public void deleteMessage(long id) {        SQLiteDatabase database = getWritableDatabase();        database.delete(                MessageTable.TABLE_NAME,                MessageTable.COLUMN_NAME_ID + " = ?",                new String[] {String.valueOf(id)});    }

修改数据

    public void updateMessageState(long id, int state) {        SQLiteDatabase database = getWritableDatabase();        ContentValues contentValues = new ContentValues();        contentValues.put(MessageTable.COLUMN_NAME_STATE, state);        database.update(                MessageTable.TABLE_NAME,                contentValues,                MessageTable.COLUMN_NAME_ID + " = ?",                new String[] {String.valueOf(id)});    }

查询数据

    public List<Message> queryAllMessages() {        SQLiteDatabase database = getReadableDatabase();        List<Message> messageList = new ArrayList<>();        Cursor cursor = null;        try {            cursor = database.query(                    MessageTable.TABLE_NAME,                    projection,                    null,                    null,                    null,                    null,                    sortOrder);            if (cursor != null && cursor.moveToFirst()) {                do {                    long id = cursor.getLong(cursor.getColumnIndex(MessageTable.COLUMN_NAME_ID));                    String fromName = cursor.getString(cursor.getColumnIndex(MessageTable.COLUMN_NAME_FROM_NAME));                    String toName = cursor.getString(cursor.getColumnIndex(MessageTable.COLUMN_NAME_TO_NAME));                    long time = cursor.getLong(cursor.getColumnIndex(MessageTable.COLUMN_NAME_TIME));                    String content = cursor.getString(cursor.getColumnIndex(MessageTable.COLUMN_NAME_CONTENT));                    int state = cursor.getInt(cursor.getColumnIndex(MessageTable.COLUMN_NAME_STATE));                    Message message = new Message(id, fromName, toName, time, content, state);                    messageList.add(message);                } while (cursor.moveToNext());            }        } finally {            if (cursor != null && !cursor.isClosed()) {                cursor.close();            }        }        return messageList;    }

批量插入（事务插入）

    public void insertMessage(List<Message> messageList) {        SQLiteDatabase database = getWritableDatabase();        try {            database.beginTransaction();            for (Message message : messageList) {                ContentValues contentValues = new ContentValues();                contentValues.put(MessageTable.COLUMN_NAME_ID, message.getId());                contentValues.put(MessageTable.COLUMN_NAME_FROM_NAME, message.getFromName());                contentValues.put(MessageTable.COLUMN_NAME_TO_NAME, message.getToName());                contentValues.put(MessageTable.COLUMN_NAME_TIME, message.getTime());                contentValues.put(MessageTable.COLUMN_NAME_CONTENT, message.getContent());                contentValues.put(MessageTable.COLUMN_NAME_STATE, message.getState());                database.insertWithOnConflict(                        MessageTable.TABLE_NAME,                        null,                        contentValues,                        SQLiteDatabase.CONFLICT_REPLACE);            }            database.setTransactionSuccessful();        } finally {            database.endTransaction();        }    }

数据库升级

    @Override    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {        if (oldVersion == 1 && newVersion == 2) {            updateToVersion2(db);        }    }    private void updateToVersion2(SQLiteDatabase db) {        db.execSQL("ALTER TABLE " + MessageTable.TABLE_NAME + " ADD "                + MessageTable.COLUMN_NAME_TYPE + " INTEGER DEFAULT 1;");    }

数据库的并发访问
WAL Mode 通过同一个openHelper并发访问
Content Provider