使用 RxJava 在主线程房间执行删除

Question

我正在使用 Room 来存储有关购物车详细信息的信息。

我想detele主线程中的记录。我收到错误

无法访问主线程上的数据库，因为它可能会长时间锁定

我检查了以下链接，但请帮帮我

executing delete with room (rxjava)

How to insert data and get id as out parameter in android room and rxjava 2?

DaoAccess.java

    @Dao
    public interface DaoAccess {

        @Insert
        void insertMultipleRecord(DBProducts... universities);

        @Insert
        void insertMultipleListRecord(List<DBProducts> universities);

        @Insert
        void insertOnlySingleRecord(DBProducts university);


        @Query("SELECT * FROM DBProducts")
        LiveData<List<DBProducts>> fetchAllData();


        @Update
        void updateRecord(DBProducts university);

        @Delete
        void deleteRecord(DBProducts university);
    }

应用程序类

    public class PRApp extends Application {
        private static PRApp m_instance;
        DBHelper dbHelper;

        @Override
        public void onCreate() {
            super.onCreate();
            mInstance = this;
            prefs = new PRPrefs(this);
            m_instance = this;

            sDefSystemLanguage = Locale.getDefault().getLanguage();
            switch (sDefSystemLanguage) {
                case "en":
                    sDefSystemLanguageCode = "1";
                    break;
                case "ar":
                    sDefSystemLanguageCode = "2";
                    break;
                default:
                    sDefSystemLanguageCode = "3";
                    break;
            }
        }


        public DBHelper getRoomDB() {
            dbHelper = Room.databaseBuilder(getApplicationContext(),
                    DBHelper.class, "prasukh-db").build();
            return dbHelper;

        }



    }

我的异步任务正在运行

    new AsyncTask<Void, Void, Integer>() {
                    @Override
                    protected Integer doInBackground(Void... params) {
                        PRApp.getInstance().getRoomDB().daoAccess().deleteRecord(products.get(position));
                        return 0;
                    }

                    @Override
                    protected void onPostExecute(Integer agentsCount) {
                        Utilities.decrementBadegeCount();
                        productsArrayList.remove(position);
                        cardAdapter.notifyDataSetChanged();
                        notifyDataSetChanged();
                        hideProgressDialog();
                        setCartLayout();
                    }
                }.execute();

如何在 RxJava 中实现这一点。因为我的 DAO delete 返回 void？

Answer 1

使用fromCallable 运算符。

Observable.fromCallable(() -> {
    PRApp.getInstance().getRoomDB().daoAccess().deleteRecord(products.get(position));
    return true;
}).firstOrError()
     .subscribeOn(Schedulers.io())
     .observeOn(AndroidSchedulers.mainThread())
     .subscribe(new SingleObserver<List<String>>() {

          @Override
          public void onSubscribe(Disposable d) {

          }

          @Override
          public void onSuccess(List<String> strings) {

          }

          @Override
          public void onError(Throwable e) {

          }

      });
      // or only
      .subscribe()
      // But if an error occurred  in delete operation the app will crash

这会执行删除操作并产生一个Observable<Boolean>。

或者你可以允许使用主线程访问数据库

Room.databaseBuilder(getApplicationContext(),DBHelper.class, "prasukh-db")
        .allowMainThreadQueries()
        .build();

但由于性能原因，不鼓励这样做。