java.lang.RuntimeException:无法复制数据库文件。试图预先填充房间数据库时发生的情况

Question

我正试图用一个数据库2.db文件预填充我的Android房间，通过让这个应用程序以务实的方式生成数据库值，我从我的设备复制了这个文件。但是，在卸载和重新安装以强制构建房间数据库时，当我最初安装该应用程序时，得到了以下错误

E/AndroidRuntime: FATAL EXCEPTION: arch_disk_io_0
Process: com.Adictya.timely, PID: 16244
java.lang.RuntimeException: Exception while computing database live data.
    at androidx.room.RoomTrackingLiveData$1.run(RoomTrackingLiveData.java:92)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
    at java.lang.Thread.run(Thread.java:919)
 Caused by: java.lang.RuntimeException: Unable to copy database file.
    at androidx.room.SQLiteCopyOpenHelper.verifyDatabaseFile(SQLiteCopyOpenHelper.java:131)
    .
    .
    .
    .
 Caused by: java.io.FileNotFoundException: database/database2.db
    at com.Adictya.timely.data.TimeSlotsDAO_Impl$7.call(TimeSlotsDAO_Impl.java:313) 
    .
    .
    .

一旦我删除了.createFromAsset("database/database2.db)，应用程序就可以正常工作了，并且我已经确保了文件在资产/数据库包中。

这是我的RoomDatabase课

@Database(entities = {Classes.class, TimeSlots.class}, version = 1, exportSchema = false)
public abstract class TimeSlotsRoomDatabase extends RoomDatabase {

    public static volatile TimeSlotsRoomDatabase INSTANCE;
    public abstract ClassesDAO classesDAO();
    public abstract TimeSlotsDAO timeSlotsDAO();

    public static TimeSlotsRoomDatabase getDatabase(final Context context){
        if (INSTANCE == null){
            synchronized (TimeSlotsRoomDatabase.class){
                if (INSTANCE == null){
                    //create our db
                    INSTANCE = Room.databaseBuilder(context.getApplicationContext(),TimeSlotsRoomDatabase.class,"timeslots_db")
                            .addCallback(roomDatabaseCallback).createFromAsset("database/database2.db").fallbackToDestructiveMigration().build();
//                    INSTANCE = Room.databaseBuilder(context.getApplicationContext(),TimeSlotsRoomDatabase.class,"timeslots_db")
//                            .addCallback(roomDatabaseCallback).build();
                }
            }
        }
        return INSTANCE;
    }
    public static RoomDatabase.Callback roomDatabaseCallback = new RoomDatabase.Callback() {
        @Override
        public void onOpen(@NonNull SupportSQLiteDatabase db){
            super.onOpen(db);
            new PopulateDbAsync(INSTANCE).execute();
        }
    };

    private static class PopulateDbAsync extends AsyncTask<Void, Void, Void>{
        private final TimeSlotsDAO timeSlotsDAO;
        private final ClassesDAO classesDAO;
        public PopulateDbAsync(TimeSlotsRoomDatabase db){
            timeSlotsDAO = db.timeSlotsDAO();
            classesDAO = db.classesDAO();
        }

        @Override
        protected Void doInBackground(Void... voids) {
            timeSlotsDAO.deleteAll();
            classesDAO.deleteAll();
            //for testing
            Classes classes = new Classes("CSE1002","Microprocessor and Interfacing","Micro");
            classes = new Classes("CSE1003","Internet of Things","IOT");

            TimeSlots timeSlots = new TimeSlots("A1",0,0,"8:00 AM","Microprocessor and Interfacing","SJT-522");
            timeSlotsDAO.insert(timeSlots);

        }
    }
}

Answer 1

我犯了一个愚蠢的错误，把资产文件夹放在我的主/java目录中。就像CommonsWare指出的那样

作为src/的子目录，使其成为java/、res/等的对等目录。

再次感谢你的帮助。

Answer 2

您有一个小错误，请将.createFromAsset("database/database2.db)替换为.createFromAsset("databases/database2.db)。数据库包将是databases/，而不是enter code here

Answer 3

您应该将您的文件放在app/src/main/assets/databases/database2.db目录中，并将其地址设置为.createFromAsset("databases/database2.db")