我需要在随机键中找到现有的子项，并且我使用 OrderByChild() 和 EqualTo() 来过滤查询，但它的行为非常奇怪，有时它显示子项仅存在一个子项，有时它不起作用。
我需要检查“February_2019”的子项（date_expense）是否存在？我试过这个
主要活动
databaseReference = firebaseDatabase.getReference("Expenses_Details");
expensesaddref = databaseReference.child(username).child("Expense_Month").child(monthyr);
int currentInt=Integer.parseInt(currentdate);
numberToWord((currentInt % 100));
Log.d("date_string",String.valueOf(dateString));
final String date_expense=expensesname +"" + dateString;
final ExpenseClass expenses=new ExpenseClass(expensesname,currentdate,date_expense,totalcost);
expensesaddref.orderByChild("date_expense").equalTo(date_expense).addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
Toast.makeText(getContext(), "Expense Already exists!!", Toast.LENGTH_SHORT).show();
}
else {
String key = expensesaddref.push().getKey();
expensesaddref.child(key).setValue(expenses);
showListAdd(expensesname);
Log.d("Adding", "Data Adding");
}
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
}}
Note
如果子项已存在于数据库中，那么它应该显示 toast，但即使子项已经是数据库，费用也会再次添加
在节目中，
monthYr是 2019 年 2 月
Currentdate是当前日期
dateString是单词中的日期（即一、十一、二十）
This is the Firebase structure what Iam getting .date_expense is adding even though child is exist already
我发现下面的代码可以根据我的需要工作
ValueEventListener valueEventListener=new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
boolean isTitleAlreadyUsed = false;
for (DataSnapshot ds: dataSnapshot.getChildren()) {
if (ds.hasChild("date_expense") && (expDate.equals(ds.child("date_expense").getValue()))) {
isTitleAlreadyUsed = true;
}
}
if(isTitleAlreadyUsed){
Toast.makeText(getContext(),"Exist",Toast.LENGTH_SHORT).show();
}else
{
String key=expensesaddref.push().getKey();
expensesaddref.child(key).setValue(expenseClass);
showListAdd(lower_exp);
Toast.makeText(getContext(),"Added",Toast.LENGTH_SHORT).show();
}
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
};
expensesaddref.addListenerForSingleValueEvent(valueEventListener);