Develop Reference

Retrieve specific data

private TextView welcomeText;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_profile);
database = FirebaseDatabase.getInstance();
databaseReference = database.getReference("Users").child("name");
welcomeText = (TextView) findViewById(R.id.welcomeText);
getData();
}
private void getData() {
databaseReference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot snapshot) {
String name = snapshot.getValue(String.class);
welcomeText.setText("Welcome" + " " + name);
}
#Override
public void onCancelled(#NonNull DatabaseError error) {
Toast.makeText(ProfileActivity.this, "Fail to get data.", Toast.LENGTH_SHORT).show();
}
});
}
https://i.stack.imgur.com/RZkvW.png
So basically, I want to set the "welcomeText" to Welcome "name" from the Firebase.
But the outcome always come out Null.

Compare two different child nodes from two different parent nodes

I am trying to compare two different child nodes from two different parent nodes. The JSON structure is the following: Attending Event > postId > userId and the second one is structured as follows: Following > firebaseUserId > userId. The goal here is to compare the userId's and if I am following that userId and also that person / userId IS attending the event, then I want to populate a list with those users.
I already wrote two methods, one to get the users that I am following getFollowing(); and another to get the users that are attending the event getAttendingEvent();. Is there a way to compare the lists / usersIds from the two methods I have already written, or do I have to write a new method entirely?
I´m really not sure how to go about this… Am I on the right track with the getFriendsAttendingEvent(); method I just wrote?
FollowersActivity
public class FollowersActivity extends AppCompatActivity {
String mId;
String mTitle;
String mPostId;
List<String> mIdList;
RecyclerView mRecyclerView;
UserAdapter mUserAdapter;
List<User> mUserList;
FirebaseUser mFirebaseUser;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_followers);
mFirebaseUser = FirebaseAuth.getInstance().getCurrentUser();
Intent intent = getIntent();
mId = intent.getStringExtra("id");
mTitle = intent.getStringExtra("title");
mPostId = intent.getStringExtra("postid");
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setTitle(mTitle);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
toolbar.setNavigationOnClickListener(v -> finish());
mRecyclerView = findViewById(R.id.recycler_view);
mRecyclerView.setHasFixedSize(true);
mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
mUserList = new ArrayList<>();
mUserAdapter = new UserAdapter(this, mUserList, false);
mRecyclerView.setAdapter(mUserAdapter);
mIdList = new ArrayList<>();
switch (mTitle) {
case "Likes":
getLikes();
break;
case "Following":
getFollowing();
break;
case "Followers":
getFollowers();
break;
case "Attending Event":
getAttendingEvent();
case "Friends Attending":
// Create this method
}
}
private void getFriendsAttendingEvent(List<User> userList, List<User> userList1) {
DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Attending Events").child(mPostId);
reference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
User user = snapshot.getValue(User.class);
userList.add(user);
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
DatabaseReference reference1 = FirebaseDatabase.getInstance().getReference("Following").child(mFirebaseUser.getUid());
reference1.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
User user1 = snapshot.getValue(User.class);
userList1.add(user1);
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
// Compare the two lists user's somehow..
if (userList.equals(userList1)) {
showUsers();
}
}
private void getLikes() {
DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Likes").child(mPostId);
reference.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
mIdList.clear();
for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
mIdList.add(snapshot.getKey());
}
showUsers();
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
private void getAttendingEvent() {
DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Attending Event").child(mPostId);
reference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
mIdList.clear();
for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
mIdList.add(snapshot.getKey());
}
showUsers();
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
private void getFollowing() {
DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Following").child(mFirebaseUser.getUid());
reference.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
mIdList.clear();
for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
mIdList.add(snapshot.getKey());
}
showUsers();
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
private void getFollowers() {
DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Followers").child(mId);
reference.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
mIdList.clear();
for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
mIdList.add(snapshot.getKey());
}
showUsers();
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
private void showUsers() {
DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Users");
reference.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
mUserList.clear();
for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
User user = snapshot.getValue(User.class);
for (String id : mIdList) {
if (user != null)
if (user.getId().equals(id)) {
mUserList.add(user);
}
}
}
mUserAdapter.notifyDataSetChanged();
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
}

Add extra data to recyclerView

I've just recently started to learn some coding, a little python and java.
I'm trying to make a whatsapp clone as a test, and I've hit a wall.
Basically I have a UID showing as the name of a group chat, and I want to swap it for a groupId I have saved in firebase at the same level as the Uid.
FirebaseDatabase.getInstance().getReference().child("chat").child(chatId).child("info").child("groupId)
I've been following simcoder youtube video and there's a lot of checks and balances happening between user and chat UIDs and I'm getting lost in the middle of all that.
I've tried adding groupId to the adapter and the chatObject, and I can see the data in debug, but I just can't get it to populate the recycler view. I've had a search of the forums here, but can't quite get it to work.
I'm hoping someone can help me out, many thanks
private RecyclerView mChatList;
private RecyclerView.Adapter mChatListAdapter;
private RecyclerView.LayoutManager mChatListLayoutManager;
ArrayList<ChatObject> chatList;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_group_chat);
OneSignal.startInit(this).init();
OneSignal.setSubscription(true);
OneSignal.idsAvailable(new OneSignal.IdsAvailableHandler() {
#Override
public void idsAvailable(String userId, String registrationId) {
FirebaseDatabase.getInstance().getReference().child("user").child(FirebaseAuth.getInstance().getUid()).child("notificationKey").setValue(userId);
}
});
OneSignal.setInFocusDisplaying(OneSignal.OSInFocusDisplayOption.Notification);
Button mLogout = findViewById(R.id.logout);
Button mFindUser = findViewById(R.id.finduser);
mFindUser.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
startActivity(new Intent(getApplicationContext(), FindUserActivity.class));
}
});
mLogout.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
OneSignal.setSubscription(false);
FirebaseAuth.getInstance().signOut();
Intent intent = new Intent(getApplicationContext(), LoginActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(intent);
finish();
return;
}
});
getPermissions();
initializeRecyclerView();
getUserChatList();
}
private void getUserChatList(){
DatabaseReference mUserChatDB = FirebaseDatabase.getInstance().getReference().child("user").child(FirebaseAuth.getInstance().getUid()).child("chat");
mUserChatDB.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()){
for (DataSnapshot childSnapshot : dataSnapshot.getChildren()){
ChatObject mChat = new ChatObject(childSnapshot.getKey());
boolean exists = false;
for (ChatObject mChatIterator : chatList){
if(mChatIterator.getChatId().equals(mChat.getChatId()))
exists = true;
}
if (exists)
continue;
chatList.add(mChat);
getChatData(mChat.getChatId());
}
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
private void getChatData(String chatId) {
DatabaseReference mChatDB = FirebaseDatabase.getInstance().getReference().child("chat").child(chatId).child("info");
mChatDB.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
if(dataSnapshot.exists()){
String chatId = "";
if(dataSnapshot.child("id").getValue() != null)
chatId = dataSnapshot.child("id").getValue().toString();
for(DataSnapshot userSnapshot : dataSnapshot.child("users").getChildren()){
for(ChatObject mChat : chatList)
if(mChat.getChatId().equals(chatId)){
UserObject mUser = new UserObject(userSnapshot.getKey());
mChat.addUserToArrayList(mUser);
getUserData(mUser);
}
}
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
private void getUserData(UserObject mUser) {
DatabaseReference mUserDb = FirebaseDatabase.getInstance().getReference().child("user").child(mUser.getUid());
mUserDb.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
UserObject mUser = new UserObject(dataSnapshot.getKey());
if(dataSnapshot.child("notificationKey").getValue() != null)
mUser.setNotificationKey(dataSnapshot.child("notificationKey").getValue().toString());
for(ChatObject mChat : chatList)
for(UserObject mUserIt : mChat.getUserObjectArrayList()){
if(mUserIt.getUid().equals(mUser.getUid())){
mUserIt.setNotificationKey(mUser.getNotificationKey());
}
}
mChatListAdapter.notifyDataSetChanged();
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
private void initializeRecyclerView() {
chatList = new ArrayList<>();
mChatList = findViewById(R.id.chatList);
mChatList.setNestedScrollingEnabled(false);
mChatList.setHasFixedSize(false);
mChatListLayoutManager = new LinearLayoutManager(getApplicationContext(), RecyclerView.VERTICAL,false);
mChatList.setLayoutManager(mChatListLayoutManager);
mChatListAdapter = new ChatListAdapter(chatList);
mChatList.setAdapter(mChatListAdapter);
}

From what I see you are passing to the adapter an empty list so that's why there's not data to be displayed.
And also, where you are using mChatListAdapter.notifyDataSetChanged();, you don't set before a populated list to the adapter.
I'm not sure which is the data you want to display but you have to collect in a list from the firebase all the information you want to display, for example, if UserObject is what you want, you have to make an ArrayList<UserObject>, to add there all the objects, pass it to the adapter and then call adapter.notifyDataSetChanged() .
You can make function in the adapter, like :
public void setData(ArrayList<YourObject> list){
yourAdapterList = list
this.notifyDataSetChanged()
}
And then call it from your activity/fragment like adapter.setData( /* your populated list */)

How to retrieve data from firebase , without changes in the data?

// This is the MainActivity, I have used firebase to store sample data, where I can update and retrieve.
But retrieval of data is possible only when there is a data change,but I want to see my data which is in firebase already
here is the data base structure]1
public class MainActivity extends
AppCompatActivity {
EditText name,weight;
Button uploadBtn;
TextView itemName,itemWeight;
DatabaseReference databaseReference=FirebaseDatabase.getInstance().getReference();
Map<String,String>values=new HashMap<>();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
name=findViewById(R.id.inputItemName);
weight=findViewById(R.id.inputItemWeight);
uploadBtn=findViewById(R.id.uploadButton);
itemName=findViewById(R.id.resultName);
itemWeight=findViewById(R.id.resultWeight);
// Here as you can see I have used an ValueEventListener to show the retrieve values from database before uploading the new Values But it is not working , unless the values of data are changed (that is it works only after uploading new values).
ValueEventListener valueEventListener=new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
String nameD=(String) dataSnapshot.child("Name").getValue();
String weightD = (String) dataSnapshot.child("Weight").getValue();
itemName.setText(nameD);
itemWeight.setText(weightD+" Kg");
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
};
databaseReference.addListenerForSingleValueEvent(valueEventListener);
uploadBtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
values.put("Name",name.getText().toString());
values.put("Weight",weight.getText().toString());
databaseReference.child("UToouch").setValue(values);
}
});
databaseReference.addChildEventListener(new ChildEventListener() {
#Override
public void onChildAdded(#NonNull DataSnapshot dataSnapshot, #Nullable String s) {
}
#Override
public void onChildChanged(#NonNull DataSnapshot dataSnapshot, #Nullable String s) {
String nameDb=(String) dataSnapshot.child("Name").getValue();
String weightDb = (String) dataSnapshot.child("Weight").getValue();
itemName.setText(nameDb);
itemWeight.setText(weightDb+" Kg");
}
#Override
public void onChildRemoved(#NonNull DataSnapshot dataSnapshot) {
}
#Override
public void onChildMoved(#NonNull DataSnapshot dataSnapshot, #Nullable String s) {
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
}

To be able to get values of your Name and Weight properties, please use the following code:
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference ref = rootRef.child("UToouch");
ValueEventListener valueEventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
String name = dataSnapshot.child("Name").getValue(String.class);
String weight = dataSnapshot.child("Weight").getValue(String.class);
Log.d(TAG, name + " / " + weight);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Log.d(TAG, databaseError.getMessage()); //Don't ignore errors!
}
};
ref.addListenerForSingleValueEvent(valueEventListener);
The output in your logcat will be:
rittesh / pv

How to exit from setValue Firebase Database?

I have a code for change messageText from database entry:
#Override
public boolean onContextItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.edit:
AdapterView.AdapterContextMenuInfo tm = (AdapterView.AdapterContextMenuInfo) item.getMenuInfo();
int position = tm.position;
final DatabaseReference ref = adapter.getRef(position);
ref.child("messageUserId").addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
if (FirebaseAuth.getInstance().getCurrentUser().getUid().equals(dataSnapshot.getValue().toString())) {
ref.child("messageText").addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
input.setText(dataSnapshot.getValue().toString());
sendMessage.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
ref.child("messageText").setValue(input.getText().toString());
input.getText().clear();
Toast.makeText(Chat.this, "Изменено", Toast.LENGTH_SHORT).show();
}
});
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
break;
}
return false;
}
Code ref.child("messageText").setValue(input.getText().toString()) works excellent, but after it code starts up again from
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
input.setText(dataSnapshot.getValue().toString());
And everything goes in a circle - the data from messageText is inserted into the EditText input and I can again change the text.
How to stop executing code after first changing messageText?

ValueEventListener's onDataChange() method:
This method will be called with a snapshot of the data at this location. It will also be called each time that data changes.
With other words, even if it is a write, an update or even a delete operation, this method is triggered. This is also happening in your case, you're using the same reference ref.child("messageText") to add data and also to listen for changes and that's why you have this behaviour. This is happening over and over again. To solve this, you need to change the logic of your code, by creating two different events. onClick to write the data to the database and attach the listener so it cannot be related to that event.

Right code:
#Override
public boolean onContextItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.edit:
AdapterView.AdapterContextMenuInfo tm = (AdapterView.AdapterContextMenuInfo) item.getMenuInfo();
int position = tm.position;
editText = adapter.getRef(position);
editText.child("messageUserId").addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
if (FirebaseAuth.getInstance().getCurrentUser().getUid().equals(dataSnapshot.getValue())) {
editText.child("messageText").addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
input.setText(dataSnapshot.getValue().toString());
editMessage();
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
} else {
Toast.makeText(Chat.this, "Запрещено", Toast.LENGTH_SHORT).show();
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
return true;
}
private void editMessage() {
sendMessage.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
editText.child("messageText").setValue(input.getText().toString());
Toast.makeText(Chat.this, "Изменено", Toast.LENGTH_SHORT).show();
input.getText().clear();
sendMessage();
}
});
}
private void sendMessage() {
sendMessage.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
if (input.getText().toString().trim().equals("")) {
Toast.makeText(Chat.this, getString(R.string.edittext_null), Toast.LENGTH_SHORT).show();
} else {
FirebaseDatabase.getInstance()
.getReference()
.push()
.setValue(new ChatMessage(input.getText().toString(),
Objects.requireNonNull(FirebaseAuth.getInstance().getCurrentUser()).getDisplayName(),
FirebaseAuth.getInstance().getCurrentUser().getUid(),
payload,
avatar,
uploadedAttach
));
input.setText("");
}
}
});
}
It was necessary to simply return to the button its original action and use addListenerForSingleValueEvent instead addValueEventListener.