java - 如何在 firebase 数据库中检索特定子项的数据 - android studio/java？

Question

我想检索特定孩子的数据，我该如何编写代码？我尝试了很多，但没有成功：“（[就像在我的数据库中一样，如何获取特定孩子（如 lubna）的任务并获取所有孩子？

标签： javaandroidfirebaseandroid-studiofirebase-realtime-database

Answer 1

初始化类变量：

private DatabaseReference mDatabase;
mDatabase = FirebaseDatabase.getInstance().getReference();
private DatabaseReference  lubnaRef = mDatabase.child("tasks/Lubna");

然后出于测试目的，我假设您在onCreate活动方法中调用它，假设您没有数据模型，您将添加以下内容：

lubnaRef.addListenerForSingleValueEvent(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        //These are all of your children.
        Map<String, Object> lubna = (Map<String, Object>) dataSnapshot.getValue();


        for (String childKey: lubna.keySet()) {
            //childKey is your "-LQka.. and so on"
            //Your current object holds all the variables in your picture.
            Map<String, Object> currentLubnaObject = (Map<String, Object>) lubna.get(childKey);

            //You can access each variable like so: String variableName = (String) currentLubnaObject.get("INSERT_VARIABLE_HERE"); //data, description, taskid, time, title
        }
   }

   @Override
   public void onCancelled(DatabaseError databaseError) {

   }
});