Question

我想构建一个Deckbuilder，该Deckbuilder允许您将创建的套牌保存在设备本地。

Decklist存储在名为TransferDeck的Arraylist中。我想存储在房间数据库中。 我的问题是，我不知道该如何正确地填充数据库，以及数据是否来自Arraylist。

我习惯于使用Arraylist，在下面您会看到我尝试存储数据的信息：

这就是我尝试过的方法，但可惜的是不起作用：

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();
}

下面您可以找到我的其余代码，但是上面的代码应该足以弄清楚我想做什么...

我创建了SaveDeck类，该类应该能够保存具有给定Deckname的Deck ：：-

@实体公共类SaveDeck实现了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;

}

我创建了Dao类，如下所示：：-

@道公共接口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);

}

进一步创建了数据库类：

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

最后一个类是片段，我尝试在其中填充数据库，而在populateDB()类中是问题

公共类review_fragment扩展了片段{

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();
}

}

Answer 1

我想提到这应该是评论而不是答案。

首先，使用AysncTask或更强大的Executors.newSingleThreadExecutor()。如果您喜欢第二个，那么最好创建一个辅助类(example)。示例：

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

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

    });
}

（1）创建一个空白的构造函数。

（4）不应在此处初始化Room Database，最好是Singleton。因此您的数据库类（3）可能像这样：

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。

使用Arraylist填充会议室数据库

1 个答案: