从 Room 数据库中获取对象，并检查前台服务的最大风速

Question

I am working in android studios, where I've loaded a room database with surfspots. I would like to build a notifikation service(foregroundservice) that checks which place there is most wind. When getting all the spots fro the DAO as a List, it says it can't run on the main thread. can someone help make a solution with LiveData?

DAO

@Dao
public interface SurfSpotDAO {

    @Query("SELECT * FROM surfSpot")
    LiveData<List<SurfSpot>> getAllSpots();

    // Get all spots from database
    @Query("SELECT * FROM surfSpot")
    LiveData<List<SurfSpot>> getAll();

    // Get specific spot from database
    @Query("SELECT * FROM surfSpot WHERE surfSpotID LIKE :spotID")
    LiveData<SurfSpot> getSpot(int spotID);

    // Add spot to database
    @Insert(onConflict = OnConflictStrategy.IGNORE)
    void addSpot(SurfSpot spot);

    // Update spot information in database
    @Update
    void updateSpot(SurfSpot spot);

    // Delete spot from database
    @Delete
    void delete(SurfSpot spot);
}

Repository

public List<SurfSpot> getAllSpots() {
         return db.surfSpotDAO().getAllSpots();
    }

The method in Foregroundservice

 Repository repository;                  // Handle API calls via repository
    public SurfSpot maxwindSpot = new SurfSpot();

    List<SurfSpot> spots;
@RequiresApi(api = Build.VERSION_CODES.N)
    private void getWind() {
        spots = repository.getAllSpots();
        maxwindSpot = Collections.max(spots, Comparator.comparingDouble(SurfSpot::getWindSpeed));
        getRecommendation(maxwindSpot);

Answer 1

Solution 1 (Not recommended):

Room.databaseBuilder(this, AppDatabase::class.java, "MyDatabase")
.allowMainThreadQueries() // this
.build()

Solution 2:
Use Kotlin Coroutines .

Solution 3 (Deprecated): Use AsyncTask in Java.

Solution 4: Use a separated Thread .

Solution 5: Use Executors .