为什么将孩子推送到特定父母后recyclerView没有更新？

Question

在将子添加到特定父级后，我尝试更新 recyclerView。 由于某种原因它没有更新，我无法弄清楚原因。 这是我的数据库架构

这里有两种方法“retrieveChildrenFromDB”用于检索特定父母的孩子

 public void retrieveChildrenFromDB() {
    accountRef.orderByChild("id").equalTo(parentId).addListenerForSingleValueEvent(new 
 ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            //loop through accounts to find the parent with that id
            for (DataSnapshot userSnapshot: dataSnapshot.getChildren()) {

                //loop through parent children to add them to adapter ArrayList
                for (DataSnapshot userchildren: 
                 userSnapshot.child("children").getChildren()) {
                    Child child = userchildren.getValue(Child.class);

                    children.add(child);
                    childsAdapter.notifyDataSetChanged();
                    childsAdapter.notifyItemRangeChanged(0, children.size());
                    recyclerView.invalidate();
                }
            }
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {
            throw databaseError.toException();
        }
    });

    recyclerView.setAdapter(childsAdapter);
    recyclerView.setLayoutManager(new LinearLayoutManager(this));
}

和“addChildToParent”将孩子添加到特定的父母

    private void addChildToParent() {
    id=new Date().getTime()+"";
    accountRef.orderByChild("id").equalTo(parentId).addListenerForSingleValueEvent(new 
       ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            for (DataSnapshot userSnapshot: dataSnapshot.getChildren()) {
                if(CheckForfileds()) {

                    userSnapshot.getRef().child("children").push()
                            .setValue(new Child(parentId,id,childAge, "0",childName,
                                  "0","0", "0"));

                   

                    childsAdapter.notifyItemRangeChanged(0, children.size());
                    recyclerView.invalidate();
                    childsAdapter.notifyDataSetChanged();
                }
            }
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {
            throw databaseError.toException();
        }
    });
}

Answer 1

我将此方法添加到我的适配器 class

   public void addItem(Child c){
    children.add(c);
    notifyDataSetChanged();
}

然后我像这样从 addChildToParent() 调用它

         childsAdapter.addItem(newChild);
         childsAdapter.notifyDataSetChanged();

它工作正常！

Answer 2

将addListenerForSingleValueEvent更改为addValueEventListener

addListenerForSingleValueEvent只会检查一次，但addValueEventListener会不断检查数据库中的任何数据变化