Question

我正在尝试使用房间库的简单数据库示例。我有一个报警类

@Entity
public class Alarm{

    @PrimaryKey
    public int id;
    public long alarmtime;

    public Alarm(int id, long alarmtime){
        this.id = id;
        this. alarmtime = alarmtime;
    }

}

AlarmDAO界面，

@Dao
public interface AlarmDAO {

    @Insert(onConflict = OnConflictStrategy.REPLACE)
    void addAlarm(Alarm alarm);

    @Query("select * from Alarm")
    public List<Alarm> getAllAlarm();

    @Query("select * from Alarm where id = :id")
    public List<Alarm> getAlarm(long userId);

    @Update(onConflict = OnConflictStrategy.REPLACE)
    void updateAlarm(Alarm alarm);

    @Query("delete from Alarm")
    void removeAllAlarm();

    }

一个AlarmDatabase类，

@Database(entities = {Alarm.class}, version = 16, exportSchema = false)
    public abstract class AlarmDatabase extends RoomDatabase {

        private static AlarmDatabase INSTANCE;

        public abstract Alarm AlarmDAO();

        public static AlarmDatabase getDatabase(Context context) {
            if (INSTANCE == null) {
                INSTANCE =
                        Room.databaseBuilder(context, AlarmDatabase.class, "userdatabase")
                                .allowMainThreadQueries()//remove this line in production
                                .fallbackToDestructiveMigration()
                                .build();
            }
            return INSTANCE;
        }
}

在我尝试从AlarmDAO访问方法的MainActivity中，它说它无法解析方法，

database = AlarmDatabase.getDatabase(this);
database.AlarmDAO().removeAllAlarm();

Answer 1

AlarmDao中没有名为AlarmDatabase的字段。您有一个名为AlarmDAO()的方法。因此，请调用AlarmDAO()方法：

database.AlarmDAO().removeAllAlarm();

Answer 2

在分析了我的所有代码后，我意识到我曾使用AlarmDAO分配给Alarm（我不知道为什么可以接受，因为它们的类型不同）所以在AlarmDatabase.java使它开始工作。

@Database(entities = {Alarm.class}, version = 16, exportSchema = false)
    public abstract class AlarmDatabase extends RoomDatabase {

    private static AlarmDatabase INSTANCE;

    public abstract AlarmDAO AlarmDAO();// WAS originally Alarm AlarmDAO();

    public static AlarmDatabase getDatabase(Context context) {
...

无法从DAO解析方法

2 个答案: