Firebase实时数据库跟踪更改 [英] Firebase realtime database tracking changes

问题描述

我正在尝试在活动的onStart方法中跟踪数据库中的所有更改，但以下代码仅在firebase树的第一个行更改时起作用：

I am trying to track all changes in the database in onStart method of an activity, but the following code works only when the first "row" of the firebase tree is changed:

mDatabase = FirebaseDatabase.getInstance().getReference();
mDatabase.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot snapshot) {
            for (DataSnapshot child : snapshot.getChildren()) {
                System.out.println(child.getKey() + " : " + child.getValue());
            }
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }

    });

我试图通过为每个孩子创建一个监听器来分别跟踪每个孩子，但它只适用于第一个孩子。如何跟踪所有这些更新？谢谢。

I tried to track each child separately by creating one listener for each child, but it worked only for the first child as well. How can I track updates for all of them? Thank you.

更新。树中有3个孩子：

Update. There are jsut 3 childs in the tree:

我需要能够看到何时更新它们。

I need to be able to see when any of them are updated.

推荐答案

尝试使用addChildEventListener：

Try using addChildEventListener:

getDatabase().getReference().addChildEventListener(new ChildEventListener() {
        @Override
        public void onChildAdded(DataSnapshot dataSnapshot, String s) {

        }

        @Override
        public void onChildChanged(DataSnapshot dataSnapshot, String s) {

        }

        @Override
        public void onChildRemoved(DataSnapshot dataSnapshot) {

        }

        @Override
        public void onChildMoved(DataSnapshot dataSnapshot, String s) {

        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    })

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