我正在嘗試從 firebase 數(shù)據(jù)庫中獲取特定值。請先查看代碼。這是數(shù)據(jù)庫參考DatabaseReference databasedeposit= FirebaseDatabase.getInstance().getReference("Deposit");totalb.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { databasedeposit.addListenerForSingleValueEvent (new ValueEventListener() { @Override public void onDataChange(DataSnapshot dataSnapshot) { abc.clear(); Integer total = 0; for (DataSnapshot ds : dataSnapshot.getChildren()) { ADeposit bazar = ds.getValue(ADeposit.class); Integer cost = Integer.valueOf(bazar.getAmount()); total = total + cost; abc.add(bazar); } Query queryn=databasedeposit.orderByChild("name").equalTo("Rabbani"); queryn.addListenerForSingleValueEvent(new ValueEventListener() { @Override public void onDataChange(DataSnapshot dataSnapshot) { Integer n_total=0; for (DataSnapshot ds : dataSnapshot.getChildren()) { ADeposit bazar = ds.getValue(ADeposit.class); Integer c = Integer.valueOf(bazar.getAmount()); n_total = n_total + c; } } @Override public void onCancelled(DatabaseError databaseError) { } }); DepositList adapter = new DepositList(admininterface.this,abc); deposit.setAdapter(adapter); } });}現(xiàn)在總成本很容易計算出來。但是來自用戶的特定數(shù)據(jù)，例如此處的“Rabbani”，用于檢索他的總金額我創(chuàng)建了一個查詢，但我無法從對話框之類的部分訪問 n_total 值。看一下數(shù)據(jù)庫結(jié)構(gòu)：
1 回答
蠱毒傳說
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您不需要嵌套的偵聽器來獲取Rabbani支出。由于此數(shù)據(jù)已存在于 中databasedeposit，因此您可以if在現(xiàn)有循環(huán)中使用 來跟蹤該數(shù)據(jù)：
databasedeposit.addListenerForSingleValueEvent (new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
abc.clear();
Integer total = 0;
Integer n_total=0;
for (DataSnapshot ds : dataSnapshot.getChildren()) {
ADeposit bazar = ds.getValue(ADeposit.class);
Integer cost = Integer.valueOf(bazar.getAmount());
total = total + cost;
abc.add(bazar);
if ("Rabbani".equals(ds.child("name").getValue(String.class)) {
n_total = n_total + cost;
}
}
System.out.println("total: "+total+", n_total: "+n_total);
...
}
@Override
public void onCancelled(DatabaseError databaseError) {
throw databaseError.toException(); // don't ignore errors
}
}); ;
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