Question

在firebase中，onDataChange（）函数被多次调用，经过一些搜索，我发现它将被称为监听器连接的次数。但是我已经多次附加了监听器，因为我需要不同的查询并获取不同类型的数据库。我怎样才能解决这个问题。我已经使用了addValueEventListener 9次来检索或排序存储在数据库中不同节点的不同数据。获取数据的适当方法是什么。任何帮助，将不胜感激。这是我使用过代码的一些地方。

    firebaseUrl.addValueEventListener(new ValueEventListener() {
        public void onDataChange(DataSnapshot dataSnapshot) {
            String temp, temp1;
            Log.e(TAG, "onDataChange: mytime " + dataSnapshot.getValue());
            long timeStampLong = (long) dataSnapshot.child("time").child("timestamp").getValue();
            SimpleDateFormat sfd = new SimpleDateFormat("HH:mm:ss");

            temp1 = sfd.format(new Date(timeStampLong));
            try {
                if (isTimeBetweenTwoTime("08:00:00", "20:00:00", temp1)) {
                    //do something


                }
            } catch (ParseException e) {
                e.printStackTrace();
            }


        }

        public void onCancelled(DatabaseError databaseError) {

        }
    });
    firebaseUrl.child("time").child("timestamp").setValue(ServerValue.TIMESTAMP);

       DatabaseReference databaseReference = FirebaseDatabase.getInstance().getReference();
        databaseReference.addValueEventListener(new ValueEventListener() {
            public void onDataChange(DataSnapshot dataSnapshot) {
                String temp1;
                long timeStampLong = (long) dataSnapshot.child("time").child("timestamp").getValue();
                SimpleDateFormat sfd1 = new SimpleDateFormat("HH:mm:ss");
                temp1 = sfd1.format(new Date(timeStampLong));


                onClickShowAnswerButton(temp1);

            }

            public void onCancelled(DatabaseError databaseError) {

            }
        });

public void onClickShowAnswerButton(String time) {

    try {
        if (isTimeBetweenTwoTime("08:00:00", "20:00:00", time)) {
            showDialogBox("Today's Answer", "The answer can be seen in between 8 PM to 8 AM only");
        } else {

            DatabaseReference databaseReference = FirebaseDatabase.getInstance().getReference();
            databaseReference.addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot dataSnapshot) {
                    String correctAnswerString, yourAnswerString;
                    String title;

                    correctAnswerString = dataSnapshot.child("questions").child(imagename).child("correctAnswer").getValue(String.class);
                    yourAnswerString = dataSnapshot.child("users").child(uid).child("questions").child(imagename).child("yourAnswer").getValue(String.class);
                    if (correctAnswerString.equals(yourAnswerString))
                        title = "CorrectAnswer: " + correctAnswerString + "\nCongratulations your answer answer is correct ";
                    else if (yourAnswerString == null)
                        title = "Answer: " + correctAnswerString + "\nYou haven't answered the question";
                    else
                        title = "Answer: " + correctAnswerString + "\nYour Answer: " + yourAnswerString + "\nSorry your answer is incorrect";

                    showDialogBox("Today's Answer", title);

                }

                @Override
                public void onCancelled(DatabaseError databaseError) {

                }
            });

        }
    } catch (ParseException e) {
        e.printStackTrace();
    }
}

Answer 1

IMO你应该做的是连接一次监听器，然后通过缓存或持久存储使这些数据可用于其他方法。您可以创建一个在更新firebase时更新的数据对象，并可能使用数据绑定之类的东西来更新UI。但是你需要附加一个监听器，尽管有多少其他地方需要数据。您可以随时获取数据。

Firebase中的onDataChange（）被多次触发

1 个答案: