为什么价值没有增加int Firebase数据库 [英] Why the value isn't increasing int Firebase database

问题描述

我对为什么它没有增加感到困惑.实际上，我正在制作一个投票面板，用户可以在其中进行投票，并且在投票时，它可以增加数据库.但这不会发生.

I am confused about why it is not increasing. Actually, I am making a voting panel, where user can vote and on voting, it increases database. But that doesn't happen.

int votes=0;

public void voteit(String party){
    final int[] v = {0};
    allpoliticalparty= FirebaseDatabase.getInstance().getReference().child("votes");
    allpoliticalparty.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            String value = dataSnapshot.getValue(String.class);
            v[0] =Integer.parseInt(value)+1;
        }
        @Override
        public void onCancelled(DatabaseError error) {
        }
    });
        votes=v[0]++;
    allpoliticalparty.setValue("" + votes);
}

我也尝试过静态int选票= 0；然后它仅增加一次，而没有增加.

I have also tried static int votes=0; Then it increments only once then it didn't increases.

推荐答案

这不是增加值的正确方法.因为我们正在开发可在多用户环境中使用的应用程序，所以您应该考虑使用事务.请查看以下方法，它将帮助您增加/减少 votes 属性的值:

That's not a proper way in which you should incremenet a value. Because we are developing applications that can be used in a multiuser environment, you should consider using a transaction. Please see the following method, it will help you increase/decrease the value of your votes property:

public static void setVotes(String operation) {
    DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
    DatabaseReference votesRef = rootRef.child("votes");
    votesRef.runTransaction(new Transaction.Handler() {
        @Override
        public Transaction.Result doTransaction(MutableData mutableData) {
            Integer votes = mutableData.getValue(Integer.class);
            if (votes == null) {
                return Transaction.success(mutableData);
            }

            if (operation.equals("increaseScore")) {
                mutableData.setValue(votes + 1);
            } else if (operation.equals("decreaseScore")){
                mutableData.setValue(votes - 1);
            }

            return Transaction.success(mutableData);
        }

        @Override
        public void onComplete(DatabaseError databaseError, boolean b, DataSnapshot dataSnapshot) {}
    });
}

然后用:

setScore("increaseScore");

有关更多信息，请查看有关保存数据的官方文档作为交易.

For more informations please check the official documentation regarding saving data as transactions.

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