reference.addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(@NonNull Datasnapshot datasnapshot) {

                   double total = 0;

                    for( Datasnapshot ds :datasnapshot.getchildren()) {
                        incomeinfo incomeinfo = ds.getvalue(incomeinfo.class);
                        double amount = Double.valueOf(incomeinfo.getamount());
                        total = total + amount;
                    }
                }

                @Override
                public void onCancelled(@NonNull DatabaseError databaseError) {

                }
            });

这是我添加总金额的参考代码

public class incomeinfo {

    public String payeename;
    public double amount;
    public String status;
    public String mod;
    public double total;

    public String getPayeename() {
        return payeename;
    }

    public void setPayeename(String payeename) {
        this.payeename = payeename;
    }

    public double getamount() {
        return amount;
    }

    public void setamount(double amount) {
        this.amount = amount;
    }

    public String getStatus() {
        return status;
    }

    public void setStatus(String status) {
        this.status = status;
    }

    public String getMod() {
        return mod;
    }

    public void setMod(String mod) {
        this.mod = mod;
    }

    public double getTotal() {
        return total;
    }

    public void setTotal(double total) {
        this.total = total;
    }

    public incomeinfo(String payeename,double amount,String status,String mod,double total) {
        this.payeename = payeename;
        this.amount = amount;
        this.status = status;
        this.mod = mod;
        this.total = total;
    }
}

我的incomeinfo类，用于将数据存储到Firebase

firebase overview need to add the amount sum in all the different groups click here to view the image

有人请帮我加上所有金额的总和。