首次加载后，SQLite数据库为空

Question

当我创建我的数据库并在其中插入一些项目之后我尝试读取它是空的，但这只是在我的应用程序的第一次启动时，无论如何都要刷新数据库或在插入新数据后重新加载它项目。我想从我的第一次开始，而不是从第二次开始读取它。

这是我的代码：

public class DBHelper extends SQLiteOpenHelper {

    protected SQLiteDatabase database;

    public DBHelper(Context context) {
        super(context, DBConstants.DB_NAME, null, DBConstants.DB_VERSION);
        open();
    }

    public void insertMuseum(Museum museum) {
        ContentValues cv = new ContentValues();
        cv.put(DBConstants.KEY_ID, museum.getId());
        cv.put(DBConstants.KEY_URL, museum.getImageURL());
        cv.put(DBConstants.KEY_DESCRIPTION, museum.getDescription());
        cv.put(DBConstants.KEY_LOCATION, museum.getLocation());
        cv.put(DBConstants.KEY_NAME, museum.getName());
        cv.put(DBConstants.KEY_MAP_STATUS, museum.getMapStatus());
        cv.put(DBConstants.KEY_MAP_SIZE, museum.getMapSizeKB());

        database.insert(DBConstants.DB_TABLE_MUSEUMS, null, cv);
    }

    public void insertRoom(Room room) {
        ContentValues cv = new ContentValues();
        cv.put(DBConstants.KEY_ID, room.getId());
        for (Door door : room.getDoors()) {
            cv.put(DBConstants.KEY_DOORS, door.getConnectedTo());
        }
        cv.put(DBConstants.KEY_MAP_ID, room.getMapId());
        for (QR qr : room.getQrs()) {
            cv.put(DBConstants.KEY_QRS, qr.getId());
        }
        for (MapPoint point : room.getShape()) {
            cv.put(DBConstants.KEY_SHAPE, point.getX());
        }
        database.insert(DBConstants.DB_TABLE_ROOMS, null, cv);
    }

    public void insertMap(MuseumMap map) {
        ContentValues cv = new ContentValues();
        cv.put(DBConstants.KEY_ID, map.getId());
        for (Room room : map.getRooms()) {
            cv.put(DBConstants.KEY_ROOM_ID, room.getId());
        }
        cv.put(DBConstants.KEY_MUSEUM_ID, map.getMuseumId());
        cv.put(DBConstants.KEY_ENTRANCE_ROOM_ID, map.getEntranceRoomId());
        database.insert(DBConstants.DB_TABLE_MAPS, null, cv);
    }

    public void insertDoor(Door door) {
        ContentValues cv = new ContentValues();
        cv.put(DBConstants.KEY_CONNECTED_TO, door.getConnectedTo());
        cv.put(DBConstants.KEY_X, door.getX());
        cv.put(DBConstants.KEY_Y, door.getY());
        cv.put(DBConstants.KEY_MAP_ID, door.getMapId());
        cv.put(DBConstants.KEY_ROOM_ID, door.getRoomId());
        cv.put(DBConstants.KEY_ID, door.getId());
        database.insert(DBConstants.DB_TABLE_DOORS, null, cv);
    }

    public void insertShape(MapPoint point) {
        ContentValues cv = new ContentValues();
        cv.put(DBConstants.KEY_X, point.getX());
        cv.put(DBConstants.KEY_Y, point.getY());
        cv.put(DBConstants.KEY_MAP_ID, point.getMapId());
        cv.put(DBConstants.KEY_ID, point.getId());
        cv.put(DBConstants.KEY_ROOM_ID, point.getRoomId());
        database.insert(DBConstants.DB_TABLE_SHAPE, null, cv);
    }

    public void insertQr(QR qr) {
        ContentValues cv = new ContentValues();
        cv.put(DBConstants.KEY_ID, qr.getId());
        cv.put(DBConstants.KEY_INFO, qr.getInfo());
        cv.put(DBConstants.KEY_X, qr.getX());
        cv.put(DBConstants.KEY_Y, qr.getY());
        cv.put(DBConstants.KEY_MAP_ID, qr.getMapId());
        cv.put(DBConstants.KEY_ROOM_ID, qr.getRoomId());
        database.insert(DBConstants.DB_TABLE_QRS, null, cv);
    }

    private void open() {
        database = this.getWritableDatabase();
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(createMuseumTable());
        db.execSQL(createMapTable());
        db.execSQL(createRoomsTable());
        db.execSQL(createQrsTable());
        db.execSQL(createDoorsTable());
        db.execSQL(createShapeTable());
    }

    private String createDoorsTable() {
        return "CREATE TABLE IF NOT EXISTS " + DBConstants.DB_TABLE_DOORS + " (_id INTEGER PRIMARY KEY AUTOINCREMENT, "
                + DBConstants.KEY_CONNECTED_TO + " TEXT, "
                + DBConstants.KEY_MAP_ID + " TEXT, "
                + DBConstants.KEY_ID + " TEXT, "
                + DBConstants.KEY_ROOM_ID + " TEXT, "
                + DBConstants.KEY_X + " REAL, "
                + DBConstants.KEY_Y + " REAL);";
    }

    private String createShapeTable() {
        return "CREATE TABLE IF NOT EXISTS " + DBConstants.DB_TABLE_SHAPE + " (_id INTEGER PRIMARY KEY AUTOINCREMENT, "
                + DBConstants.KEY_X + " REAL, "
                + DBConstants.KEY_ROOM_ID + " TEXT, "
                + DBConstants.KEY_MAP_ID + " TEXT, "
                + DBConstants.KEY_ID + " TEXT, "
                + DBConstants.KEY_Y + " REAL);";
    }

    private String createRoomsTable() {
        return "CREATE TABLE IF NOT EXISTS " + DBConstants.DB_TABLE_ROOMS + " (_id INTEGER PRIMARY KEY AUTOINCREMENT, "
                + DBConstants.KEY_DOORS + " TEXT, "
                + DBConstants.KEY_ID + " TEXT, "
                + DBConstants.KEY_SHAPE + " REAL, "
                + DBConstants.KEY_MAP_ID + " TEXT, "
                + DBConstants.KEY_QRS + " TEXT);";
    }

    private String createMapTable() {
        return "CREATE TABLE IF NOT EXISTS " + DBConstants.DB_TABLE_MAPS + " (_id INTEGER PRIMARY KEY AUTOINCREMENT, "
                + DBConstants.KEY_ROOM_ID + " TEXT, "
                + DBConstants.KEY_ID + " TEXT, "
                + DBConstants.KEY_MUSEUM_ID + " INT, "
                + DBConstants.KEY_ENTRANCE_ROOM_ID + " TEXT);";
    }

    private String createMuseumTable() {
        return "CREATE TABLE IF NOT EXISTS " + DBConstants.DB_TABLE_MUSEUMS + " (_id INTEGER PRIMARY KEY AUTOINCREMENT, "
                + DBConstants.KEY_ID + " INT, "
                + DBConstants.KEY_DESCRIPTION + " TEXT, "
                + DBConstants.KEY_LOCATION + " TEXT, "
                + DBConstants.KEY_NAME + " TEXT, "
                + DBConstants.KEY_URL + " TEXT, "
                + DBConstants.KEY_MAP_STATUS + " INT, "
                + DBConstants.KEY_MAP_SIZE + " INT);";
    }

    private String createQrsTable() {
        return "CREATE TABLE IF NOT EXISTS " + DBConstants.DB_TABLE_QRS + " (_id INTEGER PRIMARY KEY AUTOINCREMENT, "
                + DBConstants.KEY_INFO + " TEXT, "
                + DBConstants.KEY_ID + " TEXT, "
                + DBConstants.KEY_X + " REAL, "
                + DBConstants.KEY_MAP_ID + " TEXT, "
                + DBConstants.KEY_ROOM_ID + " TEXT, "
                + DBConstants.KEY_Y + " REAL);";
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

        db.execSQL("DROP TABLE IF EXISTS " + DBConstants.DB_TABLE_MUSEUMS);
        db.execSQL("DROP TABLE IF EXISTS " + DBConstants.DB_TABLE_MAPS);
        db.execSQL("DROP TABLE IF EXISTS " + DBConstants.DB_TABLE_ROOMS);
        db.execSQL("DROP TABLE IF EXISTS " + DBConstants.DB_TABLE_QRS);
        db.execSQL("DROP TABLE IF EXISTS " + DBConstants.DB_TABLE_DOORS);
        db.execSQL("DROP TABLE IF EXISTS " + DBConstants.DB_TABLE_SHAPE);
        onCreate(db);
    }

    public void museumStatusUpdate(int museumId, int mapStatus) {
        ContentValues values = new ContentValues();
        values.put(DBConstants.KEY_MAP_STATUS, mapStatus);
        database.update(DBConstants.DB_TABLE_MUSEUMS, values, DBConstants.KEY_ID + "=" + museumId, null);
    }

    public boolean isEmpty(String tableName) {
        String count = "SELECT count(*) FROM " + tableName;
        Cursor mCursor = database.rawQuery(count, null);
        mCursor.moveToFirst();
        int iCount = mCursor.getInt(0);
        mCursor.close();
        return iCount <= 0;
    }

    public void close() {
        database.close();
    }

    public Cursor getShapeValues() {
        return this.database.query(DBConstants.DB_TABLE_SHAPE, new String[]{
                        DBConstants.KEY_X, DBConstants.KEY_Y, DBConstants.KEY_ROOM_ID, DBConstants.KEY_MAP_ID, DBConstants.KEY_ID},
                null, null, null, null, null);
    }

    public Cursor getDoorValues() {
        return this.database.query(DBConstants.DB_TABLE_DOORS, new String[]{DBConstants.KEY_CONNECTED_TO,
                        DBConstants.KEY_MAP_ID, DBConstants.KEY_ROOM_ID, DBConstants.KEY_ID, DBConstants.KEY_X, DBConstants.KEY_Y},
                null, null, null, null, null);
    }

    public Cursor getQrValues() {
        return this.database.query(DBConstants.DB_TABLE_QRS, new String[]{DBConstants.KEY_ID,
                DBConstants.KEY_INFO, DBConstants.KEY_X, DBConstants.KEY_Y, DBConstants.KEY_MAP_ID,
                DBConstants.KEY_ROOM_ID}, null, null, null, null, null);
    }

    public Cursor getMuseumValues() {
        return this.database.query(DBConstants.DB_TABLE_MUSEUMS, new String[]{DBConstants.KEY_ID,
                DBConstants.KEY_DESCRIPTION, DBConstants.KEY_LOCATION, DBConstants.KEY_MAP_STATUS,
                DBConstants.KEY_NAME, DBConstants.KEY_MAP_SIZE, DBConstants.KEY_URL}
                , null, null, null, null, null);
    }

    public Cursor getRoomValues() {
        return this.database.query(DBConstants.DB_TABLE_ROOMS, new String[]{DBConstants.KEY_ID,
                DBConstants.KEY_DOORS, DBConstants.KEY_MAP_ID, DBConstants.KEY_SHAPE,
                DBConstants.KEY_QRS}, null, null, null, null, null);
    }

    public Cursor getMapValues() {
        return this.database.query(DBConstants.DB_TABLE_MAPS, new String[]{DBConstants.KEY_ID,
                DBConstants.KEY_ROOM_ID, DBConstants.KEY_MUSEUM_ID, DBConstants.KEY_ENTRANCE_ROOM_ID}
                , null, null, null, null, null);
    }
}

问题在于我尝试调用cursor.moveToFirst（）：

public void loadMuseumsList(final DownloadListener listener) {
        Cursor cursor = dbUtils.readMuseumRecord();

        if (cursor.moveToFirst()) {
            do {
                Museum museum = new Museum();
                museum.setImageURL(cursor.getString(cursor.getColumnIndex(DBConstants.KEY_URL)));
                museum.setDescription(cursor.getString(cursor.getColumnIndex(DBConstants.KEY_DESCRIPTION)));
                museum.setLocation(cursor.getString(cursor.getColumnIndex(DBConstants.KEY_LOCATION)));
                museum.setMapSizeKB(cursor.getInt(cursor.getColumnIndex(DBConstants.KEY_MAP_SIZE)));
                museum.setId(cursor.getInt(cursor.getColumnIndex(DBConstants.KEY_ID)));
                museum.setName(cursor.getString(cursor.getColumnIndex(DBConstants.KEY_NAME)));
                museum.setMapStatus(cursor.getInt(cursor.getColumnIndex(DBConstants.KEY_MAP_STATUS)));

                if (!duplicateCheck(museums, museum)) {
                    museums.add(museum);
                }
            } while (cursor.moveToNext());
        }
        listener.onMuseumListDownloaded(museums);
    }

它只是返回false。

在此方法之前，我从这里加载数据库：

public void downloadMuseumsList(final DownloadListener listener) {
        final boolean isEmpty = dbUtils.isEmpty();
        fireBaseRef.child("museums").addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                List<Museum> museums = new ArrayList<>();

                for (DataSnapshot postMuseum : dataSnapshot.getChildren()) {

                    Museum museum = postMuseum.getValue(Museum.class);

                    if (!duplicateCheck(museums, museum)) {
                        museums.add(museum);
                        dbUtils.writeMuseumRecord(museum);
                    }
                }
                if (isEmpty){
                    listener.onMuseumListDownloaded(museums);
                }
            }

            @Override
            public void onCancelled(FirebaseError firebaseError) {
                Log.e(TAG, firebaseError.toString());
            }
        });
    }

这是我在下载后编写我的记录，但之后数据库是空的，在我重新启动应用程序之后数据库就可以了。

Answer 1

我找到了解决方案！问题是我在数据库中异步录制并且代码正在进行而且数据库真的是空的：）

我改变了这一切，现在一切都好了：

public void loadContent(final DownloadListener listener) {

        if (dbUtils.isEmpty()) {
            FireBaseLoader.getInstance(context).downloadMuseumsList(new DownloadListener() {
                @Override
                public void onMuseumListDownloaded(List<Museum> museums) {
                    loadMuseumsList(listener);
                }
            });
        } else {
            FireBaseLoader.getInstance(context).downloadMuseumsList(listener);
            loadMuseumsList(listener);
        }
    }