在相同类的ondatachange中使用setvalue

Question

我想从Firebase读取数据以增加数据并写回Firebase。这是我的功能：

        StatData = FirebaseDatabase.getInstance().getReference("Statistic");

        Getstat = FirebaseDatabase.getInstance().getReference("Statistic");
        Getstat.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                Stat stat = dataSnapshot.getValue(Stat.class);
                int count = stat.getStatP();
                int statP = count + 1;
                Stat a = new Stat(statP);
                StatData.setValue(a);

            }

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

            }
        });

我正在使用同一类Stat来读写数据。可以使用吗？

Answer 1

基于该节点的当前值use a Firebase transaction将值写入该节点。您的示例如下所示：

postRef.runTransaction(new Transaction.Handler() {
    @Override
    public Transaction.Result doTransaction(MutableData mutableData) {
        Stat stat = mutableData.getValue(Stat.class);
        if (stat == null) {
            // Node doesn't exist or its value isn't known yet => return success
            return Transaction.success(mutableData);
        }
        int count = stat.getStatP();
        int statP = count + 1;
        stat = new Stat(statP);

        // Set value and report transaction success
        mutableData.setValue(p);
        return Transaction.success(mutableData);
    }

    @Override
    public void onComplete(DatabaseError databaseError, boolean b, DataSnapshot dataSnapshot) {
        // Transaction completed
        Log.d(TAG, "statTransaction:onComplete:" + databaseError);
    }
});