SQLite返回空值

Question

我正在订购应用程序
我正在使用Android studio和firebase数据库，我也在使用sqlite（因为我只是按照youtube上的教程）每当我向我的购物车添加订单时它返回空值

这是我的数据库类

public class Database extends SQLiteAssetHelper{
private static final String DB_NAME="Jerson.db";
private static final int DB_VER=1;

public Database(Context context)
{
    super(context, DB_NAME,null,DB_VER);
}

public List<Order> getCarts()
{
    SQLiteDatabase db = getReadableDatabase();
    SQLiteQueryBuilder qb = new SQLiteQueryBuilder();

    String[] sqlSelect={"MenuId","Name","Quantity","Price"};
    String sqlTable="OrderDetails";

    qb.setTables(sqlTable);
    Cursor c = qb.query(db,sqlSelect,null,null,null,null,null);

    final List<Order> result = new ArrayList<>();
    if (c.moveToFirst())
    {
        do {
            result.add(new Order(c.getString(c.getColumnIndex("MenuId")),
                    c.getString(c.getColumnIndex("Name")),
                    c.getInt(c.getColumnIndex("Quantity")),
                    c.getInt(c.getColumnIndex("Price"))
            ));
        }while (c.moveToNext());
    }
    return  result;
}
public void addToCart(Order order)
{
    SQLiteDatabase db = getReadableDatabase();
    String query = String.format("INSERT INTO OrderDetails(MenuId,Name,Quantity,Price)VALUES('%s','%s','%s','%s')",
            order.getMenuId(),
            order.getName(),
            order.getQuantity(),
            order.getPrice());
    db.execSQL(query);
}
public void cleanCart()
{
    SQLiteDatabase db = getReadableDatabase();
    String query = String.format("DELETE FROM OrderDetails");
    db.execSQL(query);
}

以下是我在CARTclass中调用它的方式

public class Cart extends AppCompatActivity {

List<Order> cart = new ArrayList<>();
CartAdapter adapter;
RecyclerView recyclerView;
RecyclerView.LayoutManager layoutManager;

FirebaseDatabase database;
DatabaseReference requests;
TextView txtTotalPrice;
Button btnPlace;
TextView txtEmail;
private DatabaseReference userData;
private FirebaseUser currentUser;
private FirebaseAuth mAuth;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_cart);


    database = FirebaseDatabase.getInstance();
    DatabaseReference myRef =database.getReference("Food");


    requests = database.getReference("Orders");

    recyclerView = (RecyclerView) findViewById(R.id.listCart);
    recyclerView.setHasFixedSize(true);
    layoutManager = new LinearLayoutManager(this);
    recyclerView.setLayoutManager(layoutManager);

    txtTotalPrice = (TextView) findViewById(R.id.total);
    btnPlace = (Button) findViewById(R.id.btnPlaceOrder);
    txtEmail = (TextView) findViewById(R.id.txtEmail);

    btnPlace.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v)
        {
            showAlertDialog();
        }
    });

    mAuth = FirebaseAuth.getInstance();
    currentUser = mAuth.getCurrentUser();
    userData = FirebaseDatabase.getInstance().getReference().child("users").child(currentUser.getUid());

    loadListFood();
}

private void showAlertDialog() {
    AlertDialog.Builder alertDialog = new AlertDialog.Builder(Cart.this);
    alertDialog.setTitle("Any Request?");

    final EditText editText = new EditText(Cart.this);
    LinearLayout.LayoutParams lp = new LinearLayout.LayoutParams(
            LinearLayout.LayoutParams.MATCH_PARENT,
            LinearLayout.LayoutParams.MATCH_PARENT
    );
    editText.setLayoutParams(lp);
    alertDialog.setView(editText);

    alertDialog.setPositiveButton("Done", new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int which) {
            Orders request  = new Orders(
                    currentUser.getEmail(),
                    txtTotalPrice.getText().toString(),
                    editText.getText().toString(),
                    cart
            );

            requests.child(String.valueOf(System.currentTimeMillis())).setValue(request);

            new Database(getBaseContext()).cleanCart();
            Toast.makeText(Cart.this, "Thank you", Toast.LENGTH_LONG).show();
            finish();
        }

    });
    alertDialog.setNegativeButton("No", new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int which) {

        }
    });
    alertDialog.show();
}


private void loadListFood()
{
    cart = new Database(this).getCarts();
    adapter = new CartAdapter(cart,this);
    recyclerView.setAdapter(adapter);



    int total = 0;
    for(Order order : cart)
    {
        total = (order.getQuantity()) * (order.getPrice());
    }
    txtTotalPrice.setText(String.valueOf(total));
}}

这是订单类

public class Order{
private String MenuId;
private String Name;
private Integer Quantity;
private Integer Price;


public Order(String menuId, String name, Integer quantity, Integer price)
{
    MenuId = menuId;
    Name = name;
    Quantity=quantity;
    Price = price;
}

public Order()
{}

public Order(String foodId, String name, String number, Integer price) {
}

public String getMenuId() {
    return MenuId;
}

public void setMenuId(String menuId) {
    MenuId = menuId;
}

public String getName() {
    return Name;
}

public void setName(String name) { Name= name;
}

public Integer getQuantity() {
    return Quantity;
}

public void setQuantity(Integer quantity) {
    Quantity = quantity;
}

public Integer getPrice() {
    return Price;
}

public void setPrice(Integer price) {
    Price = price;
}

这是我的适配器和一个类中的viewholder

class CartViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener{
public TextView txt_cart_name,txt_price;
public ImageView img_cart_count;

private ItemClickListener itemClickListener;

public void setTxt_cart_name(TextView txt_cart_name)
{
    this.txt_cart_name = txt_cart_name;
}

public CartViewHolder(View itemView)
{
    super(itemView);
    txt_cart_name =(TextView)itemView.findViewById(R.id.cart_item_name);
    txt_price =(TextView)itemView.findViewById(R.id.cart_item_price);
    img_cart_count =(ImageView) itemView.findViewById(R.id.cart_item_count);
}

@Override
public void onClick(View v)
{

}}public class CartAdapter extends RecyclerView.Adapter<CartViewHolder>{
private List<Order> listData = new ArrayList<>();
private Context context;


public CartAdapter(List<Order> listData, Context context)
{
    this.listData = listData;
    this.context = context;
}


@Override
public CartViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    LayoutInflater inflater = LayoutInflater.from(context);
    View itemView = inflater.inflate(R.layout.cartlayout,parent,false);
    return new CartViewHolder(itemView);
}

@Override
public void onBindViewHolder(CartViewHolder holder, int position) {
    TextDrawable drawable = TextDrawable.builder()
            .buildRound(""+listData.get(position).getQuantity(), Color.RED);
    holder.img_cart_count.setImageDrawable(drawable);


    int price=(listData.get(position).getPrice())*(listData.get(position).getQuantity());
    holder.txt_price.setText(String.valueOf(price));
    holder.txt_cart_name.setText(listData.get(position).getName());

}
public int getItemCount() {
    return listData.size();
}}

这是我的火炬数据库中的示例

enter image description here 它显示在您可以订购的购物车中，它将转到firebase数据库，但值为null

请帮助谢谢！