I'm building an app that is basically a table for soccer that updates every time I change it in my DB.
I'm using Firebase in this way:
I'm trying to use an addValueEventListener, but I don't know which one of the values is the one that changes (dif,score,points...) therefore I don't which field in my table I should update.
public class table extends AppCompatActivity {
Button insert;
TextView name, games, win, lost, tie, score, dif, points;
Team A;
DatabaseReference mRootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference FootballRef = mRootRef.child("Football");
DatabaseReference HouseARef = FootballRef.child("HouseA");
protected void onStart() {
super.onStart();
ValueEventListener postListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
// Get Post object and use the values to update the UI
String key = dataSnapshot.getKey() ;
Toast.makeText(table.this,key, Toast.LENGTH_SHORT).show();
// ...
}
#Override
public void onCancelled(DatabaseError databaseError) {
// Getting Post failed, log a message
// ...
}
};
HouseARef.addValueEventListener(postListener);
}
}
See here, when let's say I'm updating the name of housaA, I want to get back the key that got updated (in my case, name), but when I'm using
dataSnapshot.getKey() the Toast I'm getting back is HouseA and not name.
You won't be able to do this using a valuelistener.
Instead put a childeventlistener on the houseA.
Now inside onChildChanged, you should get the child node under houseA which has changed as a datasnapshot and from this snapshot, you can get the key which has changed
Related
so basically my problem is kind of weird. It updates the values however, I need to close the app again in order for me to update the fields again.
Here is my update code.
saveEditProfile_studentbtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
FirebaseAuth firebaseAuth = FirebaseAuth.getInstance();
String studentUser = firebaseAuth.getCurrentUser().getUid();
final DatabaseReference databaseReference = FirebaseDatabase.getInstance().getReference("Users").child(studentUser);
Toast.makeText(StudentProfileEditAct.this, studentUser, Toast.LENGTH_SHORT).show();
databaseReference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot snapshot) {
String replaceName = studentChangeFullName.getText().toString().trim();
String replacePhoneNumber = studentChangePhoneNum.getText().toString().trim();
Map<String, Object> updates = new HashMap<>();
updates.put("fullName", replaceName);
updates.put("phoneNumber", replacePhoneNumber);
databaseReference.updateChildren(updates);
Toast.makeText(StudentProfileEditAct.this, "Changes has been made", Toast.LENGTH_SHORT).show();
}
#Override
public void onCancelled(#NonNull DatabaseError error) {
}
});
}
});
and here's my realtime database. I just want to change the name and the phone number.
But for some strange reason, it logout the current user and relog it back and when i'll try to update the values, the values from the realtime (fullname,phonenumber) the data goes back from the old value and new value and it's highlighted as yellow.
The images below when I tried to update the second time around without closing the app first.
If you want to update a value in the database based on its current value, you should use a transaction to prevent conflicting writes.
But in your code, I see no reason to first read the user node before updating it. You can use this much simpler code, which may solve your problem:
public void onClick(View v) {
FirebaseAuth firebaseAuth = FirebaseAuth.getInstance();
String studentUser = firebaseAuth.getCurrentUser().getUid();
final DatabaseReference databaseReference = FirebaseDatabase.getInstance().getReference("Users").child(studentUser);
String replaceName = studentChangeFullName.getText().toString().trim();
String replacePhoneNumber = studentChangePhoneNum.getText().toString().trim();
Map<String, Object> updates = new HashMap<>();
updates.put("fullName", replaceName);
updates.put("phoneNumber", replacePhoneNumber);
databaseReference.updateChildren(updates);
Toast.makeText(StudentProfileEditAct.this, "Changes has been made", Toast.LENGTH_SHORT).show();
}
One quick fix is to use the .setValue property in the Database Reference.
You may use a model class if you intended to change different fields at once.
Based on firebase documentation, valueeventlisteners are generally made for reading and listening to data changes and not writing which might be the problem of your code
String userID = user.getUid();
mFirebaseDatabase = FirebaseDatabase.getInstance();
I have userId of the user so when I'm opening my app for the 2nd time(after signing in) I should not show the select user type layout. So I ve to check whether the use is Customer or Staff internally. So the problem is I ve to check the User Id is there . I couldn't find any method to get whether user Id is there or not! There is method called addListenerForSingleValueEvent but that won't help me in my scenario. Pic of the database is given here
I don't know how to continue after this
mFirebaseDatabase.getReference().child("Users").child("Customers")
To check if an user exists in a particular section of your Firebase database, first you need to add a listener and then use exists() method directly on the dataSnapshot object. So, asumming that Users node is a direct child of the Firebase-database root, please use the following code:
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference customersRef = rootRef.child("Users").child("Customers").child(userID);
ValueEventListener eventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if(dataSnapshot.exists()) {
//do somethig
} else {
//do something else
}
}
#Override
public void onCancelled(DatabaseError databaseError) {}
};
customersRef.addListenerForSingleValueEvent(eventListener);
I am storing user details 'firstname' and 'lastname' in UserNode. But when i want to retrieve that details then no data is being retrieved. I tried almost all solutions on the internet but nothing solved my problem. Here is my code for retrieving data of the current user:
FirebaseUser userr = FirebaseAuth.getInstance().getCurrentUser();
if (userr != null) {
String name = userr.getDisplayName();
Log.e("value", name);
}
but it says "println needs a message"
I also tried with this but nothing happened:
DatabaseReference DataRef;
DataRef = FirebaseDatabase.getInstance().getReference().child("UserNode");
DataRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
String acctname = (String)dataSnapshot.child("firstname").getValue();
Log.e("name", acctname);
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
]1
Please help me I am stuck with it
You're reading a collection of user with a ValueEventListener. As the [Firebase documentation for reading lists with a value event](Listen for value events) explains:
While using a ChildEventListener is the recommended way to read lists of data, there are situations where attaching a ValueEventListener to a list reference is useful.
Attaching a ValueEventListener to a list of data will return the entire list of data as a single DataSnapshot, which you can then loop over to access individual children.
Even when there is only a single [child node], the snapshot is still a list; it just contains a single item. To access the item, you need to loop over the result.
So in your code:
DatabaseReference DataRef;
DataRef = FirebaseDatabase.getInstance().getReference().child("UserNode");
DataRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot childSnapshot: dataSnapshot.getChildren()) {
String acctname = (String)childSnapshot.child("firstname").getValue();
Log.i("name", acctname);
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
throw databaseError.toException(); // don't ignore errors
}
});
Using FirebaseUser:
FirebaseUser implements UserInfo and in UserInfo's getDisplayName() documentation says
Returns the user's display name, if available.
So, it is possible that FirebaseUser.getDisplayName() return null when display name is not set. In that case Log.e() receives null as message and therefore prints println needs a message
Using your own structure:
Instead of using type conversion use getValue(Class<T>) like so:
String acctname = dataSnapshot.child("firstname").getValue(String.class);
Please, read how to retrieve data from firebase. I think you have a problem because you don't have Class Model.
Your steps:
Create model UserModel with firstname and lastname field
Use listener (example from docs):
// Attach a listener to read the data at our posts reference
ref.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
Post post = dataSnapshot.getValue(Post.class);
System.out.println(post);
}
#Override
public void onCancelled(DatabaseError databaseError) {
System.out.println("The read failed: " + databaseError.getCode());
}
});
See other answers: How to retrieve data from one single userID Firebase Android and retrieving data from firebase android
I'm trying to display the "loc" of a part if its part number I given.
Here is what the data structure looks like:
{
"parts":{
"14521845": { "name":"TOOL EC160B/EC180B/EC210B/EC240", "loc":"EXC1", "sloc":"B3EGU01C03"},
"12829050": { "name":"SWITCH; IGNITION SWITCH", "loc":"PS01", "sloc":"85-06-013"},
"12829050": { "name":"SWITCH; IGNITION SWITCH", "loc":"COM1", "sloc":"B3RGK03D06"},
"20044893": { "name":"PARTS CATALOG_ENG_SPA_FRE_GER_KOR_EC210D", "loc":"EXC1", "sloc":"B3EGT01B02"}
}
}
Activity Code:
FirebaseDatabase firebaseDatabase=FirebaseDatabase.getInstance();
DatabaseReference databaseReference =firebaseDatabase.getReference("parts/"+curP);
databaseReference.addChildEventListener(new ChildEventListener() {
#Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
Products data=dataSnapshot.getValue(Products.class);
Log.i("",String.valueOf(data.getLoc()));
}
getLoc is the getter function for the Product class, and it returns the corresponding "loc" for the given curP. curP denoted the child values in parts.
The logic seems right to me, but I am not getting an output. Where am I going wrong here?
try this
getReference("parts").child(curP).addChildEventListener(new ChildEventListener() {
#Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
Products data = dataSnapshot.getValue(Products.class);
Log.i("", String.valueOf(data.getLoc()));
}
});
The problem is that what you are getting in onChildAdded() is not a whole Product object as you expect it to be.
In your database reference you are targeting a specific Product ("parts/"+curP) but using a ChildEventListener. The children of a specific product node are name, loc and sloc, so the onChildAdded() will trigger several times, giving you each of these properties as a dataSnapshot separately.
The two patterns you might use to get whole Product objects are either:
add a ChildEventListener directly to the "parts" node and you will get each of the Products as a child of that node, or;
if you are adding a listener directly to the node of a particular product, use a ValueEventListener, to get the whole of that nodes entry as one dataSnapshot.
You can try to use ValueEventListener. If you want read data once so use the addListenerForSingleValueEvent method, something like this:
private void getFirebaseLocValue(int curP) {
FirebaseDatabase firebase = FirebaseDatabase.getInstance();
DatabaseReference mDatabase = firebase.getReference("parts");
mDatabase.child(Integer.toString(curP))
.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if(dataSnapshot.hasChildren()) {
Products data = dataSnapshot.getValue(Products.class);
Log.e("TAG", data.getLoc());
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
Or you can use addValueEventListener and will get data with any changes. I really don't think that ChildEventListener is a good idea to retrieve data from Firebase.
I just started using firebase and I'm amazed of how simple are complex things, and how complex simple things can be.
I need to check if a user exists in my Firebase database, and if exists, I need to get its key and value.
I have the key and I try to find it in the DB by going to my user subtree and loking for a child with the same key (ID)
DatabaseReference root_firebase = FirebaseDatabase.getInstance().getReference();
DatabaseReference users_firebase = root_firebase.child("Users");
DatabaseReference friend_found = users_firebase.child(key_searched_friend);
once I have it I try to call some method like
friend_found.getValue();
or
friend_found.child("user_name").getValue();
But it does not exist,
this seems weird since I can do both
friend_found.getKey();
friend_found.child("user_name").getKey();
I can't do this with the overriden method onDataChanged() since the data does not change when I query for this value.
This is my firebase database structure:
{
"RoomNames" : {
"Room-KM5cof0jcoMN8a4g6vC" : {
"room_name" : "TESTrOOM"
},
"Room-KM5dg_WPRdEOT4_oJ1r" : {
"room_name" : "testRoom2"
}
},
"Users" : {
"User-KM5ZaGq0xvjQis05CPF" : {
"user_name" : "Enrique"
}
}
}
You say: I can't do this with the overriden method onDataChanged() since the data does not change when I query for this value
The guide for how to Retrieve Data explains that:
Firebase data is retrieved by attaching an asynchronous listener to a
FirebaseDatabase reference. The listener is triggered once for the
initial state of the data and again anytime the data changes.
So when you attach a listener to a location, onDataChanged() fires and gives you the current value.
In the section titled Read Data Once, the guide states:
In some cases you may want a callback to be called once and then
immediately removed, such as when initializing a UI element that you
don't expect to change. You can use the
addListenerForSingleValueEvent() method to simplify this scenario: it
triggers once and then does not trigger again.
Use as below :
friend_found.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
String value = dataSnapshot.getValue(String.class);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Log.e(TAG,"Error while reading data");
}
});
For a database reference object, the same way one can add an event listener, it can also be removed, using removeEventListener.
Instead of creating an anonymous object like this
friend_found.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
String value = dataSnapshot.getValue(String.class);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Log.e(TAG,"Error while reading data");
}
});
you can create a named object of ValueEventListener and remove it from the database reference object using removeEventListener, at the end of the onDataChange method
ValueEventListener valueEventListener = new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
String value = dataSnapshot.getValue(String.class);
friend_found.removeEventListener(valueEventListener);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Log.e(TAG,"Error while reading data");
}
});
friend_found.addValueEventListener(valueEventListener);
The code inside onDataChange method gets executed only once as the ValueEventListener object is removed as soon as the last line of the method gets executed.