使用Arraylist填充房间数据库-Java 学习之路

我想构建一个Deckbuilder，它允许您在设备上本地保存创建的套牌 .

Decklist存储在Arraylists中，名为 TransferDeck . 我想在房间数据库中存储 . My issue is, that I do not know how to populate my database correctly, with the data comming out of the Arraylist.

我习惯和Arraylist一起工作，下面你看看我存储数据的尝试：

So this is what I tried but what sadly does not work:

private void populateDB(final List<TransferDeck> mTransferDeck) {
            new Thread(new Runnable() {
                @Override
                public void run() {
                    List<SaveDeck> mSaveDeck = new ArrayList<>();
                    for(int i = 0; i<mTransferDeck.size(); i++){
                        mSaveDeck.add(new SaveDeck(i, "FirstSavedDeck", mTransferDeck.get(i).getCardImage() ,mTransferDeck.get(i).getTypeImage(), mTransferDeck.get(i).getCost(), mTransferDeck.get(i).getName(), mTransferDeck.get(i).getNumber()));
                    }
                    mSavedDecksDB.deckBuilderDao().insertCards(mSaveDeck);

                }
            }).start();
}

Below you can find the rest of my code, but the above one should be enough to make clear what I want to do...

我创建了SaveDeck类，它应该能够使用给定的Deckname保存甲板： -

@Entity公共类SaveDeck实现Serializable {@PrimaryKey（autoGenerate = true）private int _id;

public SaveDeck(int _id, String deckName, int cardImage, int typeImage, Integer cardCost, String cardName, Integer cardNumber) {
    this._id = _id;
    DeckName = deckName;
    CardImage = cardImage;
    TypeImage = typeImage;
    CardCost = cardCost;
    CardName = cardName;
    CardNumber = cardNumber;
}

@ColumnInfo(name = "DeckName")
private String DeckName;

@ColumnInfo(name = "CardImage")
private int CardImage;

@ColumnInfo(name = "TypeImage")
private int TypeImage;

@ColumnInfo(name = "CardCost")
private Integer CardCost;

@ColumnInfo(name = "CardName")
private String CardName;

@ColumnInfo(name = "CardNumber")
private Integer CardNumber;

}

我按如下方式创建了Dao类:: -

@Dao公共接口DeckBuilderDao {

@Insert(onConflict = OnConflictStrategy.IGNORE)
public long[] insertCards(SaveDeck... saveDecks);

@Insert(onConflict = OnConflictStrategy.IGNORE)
public long insertCard(SaveDeck saveDecks);

@Update
public int updateCardBaseEntries(SaveDeck... saveDecks);

@Update
public int updateCardBaseEntry(SaveDeck saveDecks);

@Delete
public int deleteCardBaseEntried(SaveDeck... saveDecks);

@Delete
public int deleteCardBaseEntry(SaveDeck saveDecks);

@Query("SELECT * FROM SaveDeck")
public SaveDeck[] getAllDecks();

//probably I do not need the getAllDecks Query. Right now I only need the following one:
@Query("SELECT * FROM SaveDeck WHERE DeckName = :NameOfDeck ORDER  BY DeckName, CardName")
public SaveDeck getOneDeck(String NameOfDeck);

}

此外创建了DataBase类：

@Database(entities = {SaveDeck.class}, version = 1)
public abstract class SaveDecksDataBase extends RoomDatabase {
    public abstract DeckBuilderDao deckBuilderDao();
}

最后一个类是一个片段，我尝试填充我的数据库，而 populateDB() 类是问题

public class review_fragment extends Fragment {

private List<TransferDeck> mTransferDeck = DataHolder.getInstance().savedDecklistTransfer;
SaveDecksDataBase mSavedDecksDB;
Cursor mCursor;

public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
//return super.onCreateView(inflater, container, savedInstanceState);
    View view = inflater.inflate(R.layout.review_fragment, container, false);

    /*Introduce Cards Recycler*/

    RecyclerView rvCards = view.findViewById(R.id.rv_review_cardlist);
    rvCards.setLayoutManager(new GridLayoutManager(getActivity(), 5));
    review_RViewAdapter_Cards adapterCards = new review_RViewAdapter_Cards(getContext(), mTransferDeck);
    rvCards.setAdapter(adapterCards);



    /*Init Room database*/
    mSavedDecksDB = Room.databaseBuilder(getActivity(),SaveDecksDataBase.class,"SavedDecksDB.db").build();
    populateDB(mTransferDeck);

    return view;
}

private void populateDB(final List<TransferDeck> mTransferDeck) {
    new Thread(new Runnable() {
        @Override
        public void run() {
            List<SaveDeck> mSaveDeck = new ArrayList<>();
            for(int i = 0; i<mTransferDeck.size(); i++){
                mSaveDeck.add(new SaveDeck(i, "FirstSavedDeck", mTransferDeck.get(i).getCardImage() ,mTransferDeck.get(i).getTypeImage(), mTransferDeck.get(i).getCost(), mTransferDeck.get(i).getName(), mTransferDeck.get(i).getNumber()));
            }
            mSavedDecksDB.deckBuilderDao().insertCards(mSaveDeck);

        }
    }).start();
}

}

1 回答

我想提一下，这应该是一个评论而不是一个答案 .

首先，使用AysncTask或使用更强大的 Executors.newSingleThreadExecutor() . 如果您更喜欢第二个，那么最好是创建一个帮助类(example) . 例：

private void populateDB(final List<TransferDeck> mTransferDeck) {
    AppExecutors.diskIO().execute(() -> {

        for(int i = 0; i<mTransferDeck.size(); i++){
            mSavedDecksDB.deckBuilderDao().insertCards(new SaveDeck(...);
        }

    });
}

（1）创建一个空白构造函数 .

（4）房间数据库不应该在那里初始化，如果它是单身的话最好 . 所以你的数据库类（3）可以是这样的：

public abstract class SaveDecksDataBase extends RoomDatabase {

   private static SaveDecksDataBase sINSTANCE;
   private static final Object LOCK = new Object();

   public static SaveDecksDataBase getDatabase(final Context context) {
        if (sINSTANCE == null) {
            synchronized (LOCK) {
                if (sINSTANCE == null) {
                    sINSTANCE = Room.databaseBuilder(context.getApplicationContext(),
                            SaveDecksDataBase.class, "SavedDecksDB.db")
                            .build();
                }
            }
        }
        return sINSTANCE;
    }

    public abstract DeckBuilderDao deckBuilderDao();
}

最后，要获取 SaveDeck 对象，您还必须使用 Executors 或 AsyncTask 在后台进行工作，然后填充 RecyclerView .

回复于 2024-04-29T15:43:31+08:00

使用Arraylist填充房间数据库

1 回答

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