returns List<Object> 冻结应用程序的房间查询

Question

我尝试使用下面的代码从我的数据库中加载一些数据并将它们显示在 activity:

PhoneNumberViewModel phoneNumberViewModel =
        new ViewModelProvider(WorksideContactCard.this).get(PhoneNumberViewModel.class);

phoneNumberViewModel
    .getPhoneNumbersById(contactID)
    .observe(this,
             numbers -> {
                 phoneNumberList = numbers;
             });

准确的说，我不需要观察数据变化，因为activity恢复后数据会刷新。但是上面的代码冻结了我的应用程序，尽管我在我的另一个 class.

中使用 AsyncTask 访问数据库

为什么会这样？

编辑：

PhoneNumberViewModel.class:

public class PhoneNumberViewModel extends AndroidViewModel {
    private PhoneNumberRepository phoneNumberRepository;
    private LiveData<List<PhoneNumber>> allPhoneNumbers;

    public PhoneNumberViewModel(@NonNull Application application) {
        super(application);
        phoneNumberRepository = new PhoneNumberRepository(application);
        allPhoneNumbers = phoneNumberRepository.getAllPhoneNumbersLive();
    }

    public void insert(PhoneNumber phoneNumber) {
        System.out.println("[PhoneNumberRepository] Adding new phoneNumber");
        phoneNumberRepository.insert(phoneNumber);
    }

    public void update(PhoneNumber phoneNumber) {
        phoneNumberRepository.update(phoneNumber);
    }

    public void delete(PhoneNumber phoneNumber) {
        phoneNumberRepository.delete(phoneNumber);
    }

    public LiveData<List<PhoneNumber>> getAllPhoneNumbers() {
        return allPhoneNumbers;
    }

    public LiveData<List<PhoneNumber>> getPhoneNumbersById(long contactId)
            throws ExecutionException, InterruptedException {
        return phoneNumberRepository.getPhoneNumbersByContactId(contactId);
    }

PhoneNumberRepository.class

public class PhoneNumberRepository {
    private PhoneNumberDao phoneNumberDao;
    private LiveData<List<PhoneNumber>> allPhoneNumbers;
    private LiveData<List<PhoneNumber>> phoneNumbersByIdList;

    public PhoneNumberRepository(Application application) {

        WorksideDatabase database = WorksideDatabase.getInstance(application);
        phoneNumberDao = database.phoneNumberDao();
        allPhoneNumbers = phoneNumberDao.getAllPhoneNumbers();
    }

    ...

    public LiveData<List<PhoneNumber>> getAllPhoneNumbersLive() {
        return allPhoneNumbers;
    }

    public void deleteAllPhoneNumbers() {
        new DeleteAllPhoneNumbersAsyncTask(phoneNumberDao).execute();
    }

    public LiveData<List<PhoneNumber>> getPhoneNumbersByContactId(long id)
            throws ExecutionException, InterruptedException {
        return new SelectPhoneNumberByIdAsyncTask(phoneNumberDao, id).get();
    }

    private static class SelectPhoneNumberByIdAsyncTask
            extends AsyncTask<Long, Void, LiveData<List<PhoneNumber>>> {

        private PhoneNumberDao phoneNumberDao;
        private Long ID;

        private SelectPhoneNumberByIdAsyncTask(PhoneNumberDao phoneNumberDao, Long contactId) {
            this.phoneNumberDao = phoneNumberDao;
            ID = contactId;
        }

        @Override
        protected LiveData<List<PhoneNumber>> doInBackground(Long... contactId) {

            ID = contactId[0];

            return phoneNumberDao.getPhoneNumbersById(ID);
        }
    }

    ...
}

PhoneNumberDao.class:

@Dao
public interface PhoneNumberDao {

    @Insert
    void insert(PhoneNumber phoneNumber);

    @Update
    void update(PhoneNumber phoneNumber);

    @Delete
    void delete(PhoneNumber phoneNumber);

    // Probably uneeded method
    @Query("DELETE FROM phone_numbers_table")
    void deleteAllPhoneNumbers();

    // Delete entry/entries by ID
    @Query("DELETE FROM phone_numbers_table WHERE id = :phoneNumberId")
    void deleteByPhoneNumberId(long phoneNumberId);

    // Retrieve entry/entries by contact ID
    //    @Query("SELECT * FROM phone_numbers_table WHERE contact_id = :contactId")
    //    List<PhoneNumber> getPhoneNumbersById(long contactId);

    // Retrieve all saved phone numbers in LiveData format
    @Query("SELECT * FROM phone_numbers_table")
    LiveData<List<PhoneNumber>> getAllPhoneNumbers();

    @Query("SELECT * FROM phone_numbers_table WHERE contact_id = :contactId")
    LiveData<List<PhoneNumber>> getPhoneNumbersById(long contactId);

    @Query("SELECT * FROM phone_numbers_table")
    List<PhoneNumber> getAll();
}

Answer 1

return new SelectPhoneNumberByIdAsyncTask(phoneNumberDao, id).get();

这就是你的问题，.get() 调用阻塞了主线程我建议切换到 Kotlin 并使用协程，或者在这里你可以使用回调来处理这个问题，而不是使用 AsyncTask.get() 来阻止主要的 thread.Also 顺便说一句，我最后听说异步任务将被弃用，所以继续记住这一点。这是问题的一种解决方案

public class Repository implements 
SelectPhoneNumberByIdAsyncTask.OnPhoneNumberFound {


@Override
public void onPhoneNumberFound(LiveData<List<Object>> list) {
   //you can get the data you want here
}



} 


 class SelectPhoneNumberByIdAsyncTask extends AsyncTask<Long, Void, 
  LiveData<List<PhoneNumber//Correct this>>> {

interface OnPhoneNumberFound{
    void onPhoneNumberFound(LiveData<List<PhoneNumberDao>> list);
}
OnPhoneNumberFound mListener;


private PhoneNumberDao phoneNumberDao;
private Long ID;

private SelectPhoneNumberByIdAsyncTask(Object phoneNumberDao, Long contactId) {
    this.phoneNumberDao = phoneNumberDao;
    ID = contactId;
}

@Override
protected LiveData<List<Object>> doInBackground(Long... contactId) {
    ID = contactId[0];
    mListener.onPhoneNumberFound(phoneNumberDao.getPhoneNumbersById(ID));
    return null;
}

}

现在使用 .execute() 调用而不是 .get()

returns List<Object> 冻结应用程序的房间查询

Room query that returns List<Object> freezes application

java

android

android-asynctask

android-room