英文:
How to read data from the Firebase realtime database
问题
我想从 Firebase 实时数据库中的特定节点读取数据。
这是我的 JSON 树：
{
"user": "1",
"user_details": {
"emails": ["valker@gmail.com"],
"usernames": ["valk stone"]
}
}
我如何从 user 节点读取数据？
英文:
I want to read data from a particular node from the firebase realtime database.
This is my JSON tree:
{
"user" : "1",
"user_details" : {
"emails" : [ "valker@gmail.com" ],
"usernames" : [ "valk stone" ]
}
}
How do I read data from the user node?
答案1
得分: 1
你可以通过监听器来读取数据。如果你阅读文档，你会了解到 SingleValueEvent 用于一次性读取数据：
ValueEventListener userListener = new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
Log.d(dataSnapshot);
}
@Override
public void onCancelled(DatabaseError databaseError) {
// 获取数据失败，记录信息
Log.w(TAG, "loadPost:onCancelled", databaseError.toException());
// ...
}
};
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference usersRef = rootRef.child("user_details");
usersRef.addListenerForSingleValueEvent(userListener);
英文:
You can read data with the help of listener. If you read docs you come to know that SingleValueEventis used for read data once :
ValueEventListener userListener = new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
Log.d(dataSnapshot);
}
@Override
public void onCancelled(DatabaseError databaseError) {
// Getting Post failed, log a message
Log.w(TAG, "loadPost:onCancelled", databaseError.toException());
// ...
}
};
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference usersRef = rootRef.child("user_details");
usersRef.addListenerForSingleValueEvent(userListener);
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