Question

我有OrderCart，我想从中获取所有商品价格的总和，以便向用户显示总价

这是我的Order类，它具有字符串价格属性

public class Order {
private String mID;
private String mName;
private String mPrice;
public Order(){

}


public Order(String id, String name, String price)
{
    mID = id;
    mName = name;
    mPrice = price;
}



public String getmID() {
    return mID;
}

public String getmName() {
    return mName;
}

public String getmPrice() {
    return mPrice;
}

这是一个用于检索数据的firebase采用者的类。采用者显示OrderCart父级下的所有子项，总和应显示在采用者下方，但是它给出了错误

public class PlaceOrder extends AppCompatActivity {

private RecyclerView mOrderList;
private DatabaseReference mDatabase;
private int total_amount=0;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_open_orders);

    mOrderList = (RecyclerView) findViewById(R.id.order_layout);
    mOrderList.setHasFixedSize(true);
    mOrderList.setLayoutManager(new LinearLayoutManager(this));
    mDatabase = FirebaseDatabase.getInstance().getReference().child("OrderCart");
    FirebaseRecyclerAdapter<Order, OrderViewHolder> FBRA = new FirebaseRecyclerAdapter<Order, OrderViewHolder>(
            Order.class,
            R.layout.single_order,
            OrderViewHolder.class,
            mDatabase


    ) {
        @Override
        protected void populateViewHolder(OrderViewHolder viewHolder, Order model, int position) {

            viewHolder.setmID(model.getmID());
            viewHolder.setmName(model.getmName());
            viewHolder.setmPrice(model.getmPrice());


        }
    };

    mOrderList.setAdapter(FBRA);

    mDatabase.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {

            for (DataSnapshot snapScore : dataSnapshot.child("OrderCart").getChildren()) {
                total_amount += Integer.parseInt(String.valueOf(snapScore.child("mPrice").getValue()));
            }
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });


    TextView item_price = (TextView) findViewById(R.id.price);
    item_price.setText(total_amount);

}

现在，当我尝试显示总金额时，应用会崩溃，以便如何正确检索数据？

Answer 1

尝试这种方式，使用迭代器读取数据。

在onDataChange内部，

Iterator<DataSnapshot> dataSnapshotsorder =  dataSnapshot.child("OrderCart").getChildren().iterator();
  while (dataSnapshotsorder .hasNext()) {
            DataSnapshot dataSnapshotChild = dataSnapshotsChat.next();
            total_amount += Integer.parseInt(String.valueOf(dataSnapshotChild .child("mPrice").getValue()));                  
 }

获取Firebase的所有子条目的总和

1 个答案: