尝试预填充 ROOM 数据库时出现 java.lang.RuntimeException : Unable to copy database file.

Question

我正在尝试使用我从设备复制的 database2.db 文件预填充我的 Android ROOM，方法是让应用程序实用地生成数据库值。这在我最初安装应用程序时有效，但是在卸载和重新安装以强制构建 ROOM 数据库时，我收到以下错误

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)` 并且我确保该文件位于 assets/database 包中，应用程序就可以正常工作。

这是我的 RoomDatabase 类

@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，将 Assets 文件夹放在我的 main/java 目录中。它应该是 CommonsWare指出

as a sub-directory of src/, making it a peer of java/, res/, etc.

再次感谢您的帮助。