如何从一个用户ID获取数据Firebase Android [英] How to retrieve data from one single userID Firebase Android
问题描述
我的数据看起来像;
UserTable
{
fmXWU324VHdDb8v6h7gvNjRojnu33:{
-KbJtw467nl6p253HZ537:{
Name:name1,
Email:something1@something.com,
userid:fmXWU324VHdDb8v6h7gvNjRojnu33
}
},
pJtC45fW0MMi352UiPWnWdIS7h88:{
-Kb012ls9iMnzEL723o9I:{
Name:name2,
Email:something2@something.com,
userid:pJtC45fW0MMi352UiPWnWdIS7h88
},
-Kb0aq0q25FJq38256SrC:{
Name:name3,
Email:something3@something.com,
userid:pJtC45fW0MMi352UiPWnWdIS7h88
},
-Kb0atopfK64F6jy124Qi1u:{
Name:name3,
Email:something1 @ something.com,
userid:p JtC45fW0MMi352UiPWnWdIS7h88
}
我想说并显示该用户的所有数据fmXWU324VHdDb8v6h7gvNjRojnu33
。我不知道我该怎么做。我试过了,这似乎是合乎逻辑的,但似乎并不奏效:
df.child(UserTable)。child (user.getUid()))。addChildEventListener(new ChildEventListener()
它给出这个错误: / p>
无法将java.lang.String类型的对象转换为com.android.example.UserTable
<
另外,我也试过: c $ c> df.child(UsersTable)。child(userid)。child(user.getUid())。ad dChildEventListener(new ChildEventListener()
我似乎可以弄清楚我做错了什么,因为我所尝试过的似乎合乎逻辑,应该可以工作,请有人帮我解决。 (b)
编辑:
pre $ public ArrayList< data> get(String userID){
df.child(UsersTable)。child(userID).ad dChildEventListener(new ChildEventListener(){
@Override
public void onChildAdded(Data快照dataSnapshot,String s){
fetch(dataSnapshot);
$ b @Override
public void onChildChanged(DataSnapshot dataSnapshot,String s){
fetch(dataSnapshot);
$ b $ @覆盖
public void onChildRemoved(DataSnapshot dataSnapshot){
}
@Override
public void onChildMoved(DataSnapshot dataSnapshot,String s){
}
@Override
public void onCancelled(DatabaseError databaseError){
}
});
返回数据;
更新 (DataSnapshot ds:dataSnapshot.getChildren())
($ b $)$ private $ fetchData(DataSnapshot dataSnapshot)
{
b Userdetail userdetail = ds.getValue(Userdetail.class);
userdetails.add(userdetail);
$ / code>
像这样初始化数据库
$ $ $ $ $ $ $ $ mDatabase = FirebaseDatabase.getInstance()。getReference()。child(your_node_name);
然后设置 ValueEventListener
到您的数据库参考。
在 onDataChange
方法中,您可以像这样检索数据
public void onDataChange(DataSnapshot dataSnapshot){
User user = dataSnapshot.getValue(User.class);
$ / code>
编辑:
<$ (DataSnapshot dataSnapshot){
用户用户= dataSnapshot.getValue(User.class){p $ p $ ValueEventListener postListener = new ValueEventListener(){
@Override
public void onDataChange );
}
@Override
public void onCancelled(DatabaseError databaseError){
};
mDatabase.addValueEventListener(postListener);
In my firebase database, I have list of users that have different information under them. I would like to retrieve information from a single userId, which I will define in the code and I want to only get information from that user.
My data looks like;
UserTable
{
"fmXWU324VHdDb8v6h7gvNjRojnu33" : {
"-KbJtw467nl6p253HZ537" : {
"Name" : "name1",
"Email" : "something1@something.com",
"userid" : "fmXWU324VHdDb8v6h7gvNjRojnu33"
}
},
"pJtC45fW0MMi352UiPWnWdIS7h88" : {
"-Kb012ls9iMnzEL723o9I" : {
"Name" : "name2",
"Email" : "something2@something.com",
"userid" : "pJtC45fW0MMi352UiPWnWdIS7h88"
},
"-Kb0aq0q25FJq38256SrC" : {
"Name" : "name3",
"Email" : "something3@something.com",
"userid" : "pJtC45fW0MMi352UiPWnWdIS7h88"
},
"-Kb0atopfK64F6jy124Qi1u" : {
"Name" : "name3",
"Email" : "something1@something.com",
"userid" : "pJtC45fW0MMi352UiPWnWdIS7h88"
}
}
and I want to, say for example read and display all data from this user "fmXWU324VHdDb8v6h7gvNjRojnu33"
. I am not sure how I can do that. I tried this, which seems logical but it doesn't seem to work:
df.child("UserTable").child(user.getUid())).addChildEventListener(new ChildEventListener()
it gives this error:
Can't convert object of type java.lang.String to type com.android.example.UserTable
In addition, I have tried:
df.child("UsersTable").child("userid").child(user.getUid()).addChildEventListener(new ChildEventListener()
I can seem to figure out what I am doing wrong, as what I have tried seems logical and should work. Please can someone help me out.
EDITED:
public ArrayList<data> get(String userID){
df.child("UsersTable").child(userID).addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
fetch(dataSnapshot);
}
@Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
fetch(dataSnapshot);
}
@Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
}
@Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
return data;
Update
private void fetchData(DataSnapshot dataSnapshot)
{
for (DataSnapshot ds : dataSnapshot.getChildren())
{
Userdetail userdetail =ds.getValue(Userdetail.class);
userdetails.add(userdetail );
}
}
First initialize your database like this
mDatabase= FirebaseDatabase.getInstance().getReference().child("your_node_name");
then try setting a ValueEventListener
to your Database reference.
Inside the onDataChange
method you can retrieve your data like this
public void onDataChange(DataSnapshot dataSnapshot) {
User user= dataSnapshot.getValue(User.class);
}
EDIT:
ValueEventListener postListener = new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
User user= dataSnapshot.getValue(User.class);
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
};
mDatabase.addValueEventListener(postListener);
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