Android Firebase中的方法和分类

Question

我是一名新的Android程序员。我试图找出两个firebase结果之间的差异：Expenditure和Sale。我在一个活动中的一个类中完成了两个查询。但是，我对我编写的代码没有任何好运。目前，两种方法都返回空值。

以下是代码：

package com.example.moses.farm;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.TextView;

import com.firebase.client.FirebaseError;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;

public class LukenyaSales extends AppCompatActivity {
    private TextView profit;
    private TextView Loss;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_lukenya_sales);
        profit = (TextView) findViewById(R.id.profit);
        Loss = (TextView) findViewById(R.id.Loss);


        class Profit {

            private int Expendituree;
            private int Salee;
            private FirebaseAuth firebaseAuth;

            public int getExpenditure() {

                firebaseAuth = FirebaseAuth.getInstance();
                DatabaseReference dref = FirebaseDatabase.getInstance().getReference();
                dref.addValueEventListener(new ValueEventListener() {

                    @Override
                    public void onDataChange(DataSnapshot snapshot) {
                        int totalAmount = 0;
                        FirebaseUser user = firebaseAuth.getCurrentUser();
                        DatabaseReference dref = FirebaseDatabase.getInstance().getReference();
                        if (user != null) {
                            final String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();
                            for (DataSnapshot postSnapshot : snapshot.getChildren()) {
                                dref = dref.child(uid + "Expenditure");
                                DogExpenditure dogExpenditure = postSnapshot.getValue(DogExpenditure.class);
                                totalAmount += dogExpenditure.getAmount();
                                Expendituree = totalAmount;
                            }
                        }
                    }

                    @Override
                    public void onCancelled(DatabaseError databaseError) {
                    }

                    public void onCancelled(FirebaseError firebaseError) {
                        System.out.println("The read failed: " + firebaseError.getMessage());
                    }
                });
                return Expendituree;
            }

            public int getSale() {
                final DatabaseReference dreff = FirebaseDatabase.getInstance().getReference();
                dreff.addValueEventListener(new ValueEventListener() {
                    @Override
                    public void onDataChange(DataSnapshot snapshot) {
                        int totalAmount = 0;
                        FirebaseUser user = firebaseAuth.getCurrentUser();
                        if (user != null) {
                            final String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();
                            DatabaseReference dreff = FirebaseDatabase.getInstance().getReference();
                            for (DataSnapshot postSnapshot : snapshot.getChildren()) {
                                dreff = dreff.child(uid + "Expenditure");
                                DogExpenditure dogExpenditure = postSnapshot.getValue(DogExpenditure.class);
                                totalAmount += dogExpenditure.getAmount();
                            }
                            Salee = totalAmount;
                        }
                    }

                    @Override
                    public void onCancelled(DatabaseError databaseError) {
                    }

                    public void onCancelled(FirebaseError firebaseError) {
                        System.out.println("The read failed: " + firebaseError.getMessage());
                    }
                });
                return Salee;
            }

            int pro;
            int loss;


            public int getLoss() {
                if (Expendituree > Salee) {
                    loss = Expendituree - Salee;
                    Loss.setText("Your total Loss for this Unit is:" + Integer.toString(loss));
                }
                return loss;
            }

            public int getPro() {
                if (Expendituree < Salee) {
                    pro = Salee - Expendituree;
                    profit.setText("Your total Profit for this Unit is:" + Integer.toString(pro));

                }
                return pro;
            }
        }
    }
}