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How to sort data from Firebase realtime database?

I'm using GraphView library. My code below gets data from Firebase real-time database and updates the graph with values from database, but it isn't sorted. I need it to be sorted in ascending order in X axis. The data in X axis is Long type, then it's converted to date.
I've tried adding dp[index] to array list and using different sorting methods, but nothing seems to work.
#Override
public void onStart() {
reference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot snapshot) {
FirebaseAuth auth;
auth = FirebaseAuth.getInstance();
FirebaseUser user = auth.getCurrentUser();
String id = user.getUid();
DataPoint[] dp = new DataPoint[(int) snapshot.child(id).getChildrenCount()];
int index = 0;
for(DataSnapshot myDataSnapshot : snapshot.child(id).getChildren()){
PointValue pointValue = myDataSnapshot.getValue(PointValue.class);
dp[index] = new DataPoint(pointValue.getxValue(), pointValue.getyValue());
index ++;
}
lineGraphSeries.resetData(dp);
}
#Override
public void onCancelled(#NonNull DatabaseError error) {
}
});
super.onStart();
}
AlertDialog, where data is being written to the database:
builder.setPositiveButton("ADD",
new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialogInterface, int i) {
if(TextUtils.isEmpty(weightEditText.getText().toString()) || TextUtils
.isEmpty(dateEditText.getText().toString())) {
Toast.makeText(getActivity(),"Please provide weight and date",
Toast.LENGTH_SHORT).show();
} else{
linearLayout.addView(createNewTextView(weightEditText.getText().toString(),
dateEditText.getText().toString()));
String id = user.getUid();
String randomId = reference.push().getKey();
try {
Date date = sdf.parse(dateEditText.getText().toString());
long x = date.getTime();
int y = Integer.parseInt(weightEditText.getText().toString());
PointValue pointValue = new PointValue(x,y);
reference.child(id).child(randomId).setValue(pointValue);
} catch (ParseException e) {
e.printStackTrace();
}
}
}
});
builder.setView(view);
builder.show();
PointValue class:
public class PointValue {
long xValue;
int yValue;
public PointValue() {
}
public PointValue(long xValue, int yValue) {
this.xValue = xValue;
this.yValue = yValue;
}
public long getxValue() {
return xValue;
}
public int getyValue() {
return yValue;
}
}
#EDIT
Thanks to #Frank van Puffelen, I've managed to sort my data from Firebase Database using orderByChild()
https://firebase.google.com/docs/database/android/lists-of-data#sort_data
below working solution:
#Override
public void onStart() {
FirebaseAuth auth;
auth = FirebaseAuth.getInstance();
FirebaseUser user = auth.getCurrentUser();
String id = user.getUid();
Query dateAscendingOrder = database.getReference("users")
.child(id).orderByChild("xValue");
dateAscendingOrder.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot snapshot) {
DataPoint[] dp = new DataPoint[(int) snapshot.getChildrenCount()];
int index = 0;
for (DataSnapshot myDataSnapshot : snapshot.getChildren()){
PointValue pointValue = myDataSnapshot.getValue(PointValue.class);
dp[index] = new DataPoint(pointValue.getxValue(), pointValue.getyValue());
index++;
}
lineGraphSeries.resetData(dp);
}

retreiving sqlite and firebase data at the same time

Im retrieving a UID from sqlite and using that uid to fetch data from firebase but the problem is its only fetching the values of the first UID and not after that
Code
String userId = null;
Cursor csr = myDBHlpr.getAllQuestions4();
while (csr.moveToNext()) {
userId = csr.getString(csr.getColumnIndex(KEY_USER_ID));
}
final String uid = userId;
mUsersDatabase.child(userId).addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
mName = dataSnapshot.child("Name").getValue().toString();
String mStatus = dataSnapshot.child("Status").getValue().toString();
String mDisplayImage = dataSnapshot.child("Image").getValue().toString();
mUsers.add(new IdHelper(mName, mStatus, mDisplayImage));
mAdapter.notifyDataSetChanged();
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
The table has multiple rows with different UIDs and firebase too has multiple UID data... I have crosschecked multiple times. But still only the one item is fetched. Why is that? should i retrieve sqlite data is a string []?
Database ref is perfect and the problem according to me is that im fetching only one data as userid and im thinking it stops there so only one IDs data is getting fetched from firebase. Anyways can someone help me out please
Edit
public Cursor getAllQuestions4() {
return this.getWritableDatabase().query(TABLE_ID_DATA,null,null,null,null,null,null);
}

I guess your problem is the while loop. You are only using the last userId. So change your code as follows (please notice the change of the last bracket of your while loop):
String userId = null;
Cursor csr = myDBHlpr.getAllQuestions4();
while (csr.moveToNext())
{
userId = csr.getString(csr.getColumnIndex(KEY_USER_ID));
final String uid = userId;
mUsersDatabase.child(userId).addValueEventListener(new ValueEventListener()
{
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
mName = dataSnapshot.child("Name").getValue().toString();
String mStatus = dataSnapshot.child("Status").getValue().toString();
String mDisplayImage = dataSnapshot.child("Image").getValue().toString();
mUsers.add(new IdHelper(mName, mStatus, mDisplayImage));
mAdapter.notifyDataSetChanged();
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}

Problem with Firebase adding a fab button cant delete entry

Currently a have a floating action bottom in my detailView in this activity I bring the information of the Object with an intent. I want that when the user enters the detailView activity I have a filled heart if that Automoviles objectId already exist in the Favorites Node.if not add the information into the Database. If the favorite already exist and it has the filled heart if the user clicks again it will remove it from the database.
This is my favorites class:
public class Favorites {
private String id;
private String automovilesId;
private String userId;
private String fecha;
public Favorites() {
}
public Favorites(String automovilesId, String userId, String fecha) {
this.automovilesId = automovilesId;
this.userId = userId;
this.fecha = fecha;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getAutomovilesId() {
return automovilesId;
}
public void setAutomovilesId(String automovilesId) {
this.automovilesId = automovilesId;
}
public String getUserId() {
return userId;
}
public void setUserId(String userId) {
this.userId = userId;
}
public String getFecha() {
return fecha;
}
public void setFecha(String fecha) {
this.fecha = fecha;
}
}
At the moment i have this code:
databaseReference = FirebaseDatabase.getInstance().getReference(AppModel.Favorites);
favoritesButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
final DatabaseReference usersRef = rootRef.child("Favorites");
favorites = new Favorites(automoviles.getObjectId(), user.getUid(), AppModel.GetDate());
databaseReference.push().setValue(favorites);
}
});
Which Leads this entry in the database:
Firebase Data
This is all good but i need to verify also if favorites exist or not in the database or else everytime i run the android emulator it will create another favorites node.
Now i added more code . But when i run it and i add this AddFavorite method it will create infinite loops of Favorite Nodes in the database
databaseReference = FirebaseDatabase.getInstance().getReference(AppModel.Favorites);
favoritesButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
final DatabaseReference usersRef = rootRef.child("Favorites");
favorites = new Favorites(automoviles.getObjectId(), user.getUid(), AppModel.GetDate());
databaseReference.push().setValue(favorites);
usersRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for(DataSnapshot ds : dataSnapshot.getChildren()) {
String car = ds.child("automovilesId").getValue(String.class);
Favorites fav =ds.getValue(Favorites.class);
String carId =fav.getAutomovilesId();
Log.i("No","Este es el nombre------>:"+carId);
String id=ds.getKey();
AddFavoritesuser();
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
});
This is the AddFavorite method and the delete method:
private void AddFavoritesuser() {
favoritesButton.setImageResource(R.drawable.ic_favorite);
favorites = new Favorites(automoviles.getObjectId(), user.getUid(), AppModel.GetDate());
databaseReference.push().setValue(favorites);
}
And the delete:
private void deleteFavoritesUser(String key) {
favoritesButton.setImageResource(R.drawable.ic_favorite_border);
databaseReference.child(key).getRef().removeValue();
}
In short i want it to verify if that object of Automoviles object exist . If it exist the user enters and sees the filled heart, if he wants to delete this favorite then he clicks again and it will run the deleteFavoritesUser method. But my question is what if Favorites is still no created in the database how can i also validate this?.
I runned the app again and I have the same vale created again:
As you can see I have the same automovilesId entry

basically you need to make your favorite button as a toggle button
favoritesButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// in place of YES/NO you can take any values to present true/false state
boolean status = v.getTag() != null ? v.getTag().equals("YES") : false;
v.setTag(status ? "NO" : "YES");
if (status) {
// Do favorite me
//AddFavoritesuser();
} else {
// Do un favorite me
//deleteFavoritesUser(key);
}
}
}

everytime i run the android emulator it will create another favorites node.
This is happening because everytime you are trying to add a new object of Favorites class to the database, you are using the push() method, which generates a new random key everytime is called. This is what this method does. So in order to check a property from the database, you need to use in your reference the same key, not to generate another one. Please see in my answer from this post, where I have explained how you can achieve this.

Firebase won't trigger data change event

I am using Firebase with my Android application. I am trying to use Firebase as a NOSQL database and this is my data retrieval object.
public class FirebaseManager {
private static final String DB_REF = "mainframeradio";
private static final String STREAM_REF = "streams";
public static List<MediaStream> getMediaStreams(Context context) {
final List<MediaStream> mediaStreams = new ArrayList<>();
FirebaseDatabase db = FirebaseDatabase.getInstance();
DatabaseReference dbRef = db.getReference(STREAM_REF);
dbRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
Map<String, Object> streams = (Map<String, Object>) dataSnapshot.getValue();
if (!streams.isEmpty()) {
for (Object stream : streams.values()) {
String protocol = (String) ((Map) stream).get("protocol");
String host = (String) ((Map) stream).get("host");
int port = (int) ((Map) stream).get("port");
String media = (String) ((Map) stream).get("media");
String metadata = (String) ((Map) stream).get("metadata");
String streamName = (String) ((Map) stream).get("streamName");
MediaStream mediaStream = new MediaStream(protocol, host, port, media, metadata, streamName);
mediaStreams.add(mediaStream);
}
} else {
L.d("No media streams found on the server.");
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
L.w("Couldn't read the stream info from Firebase.");
}
});
return mediaStreams;
}
}
The thing is the event does not get triggered from the activity I am calling it from.
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_player);
// Set components.
this.playerView = findViewById(R.id.playerView);
this.songTitleTextView = findViewById(R.id.songTitleTextView);
this.albumArt = findViewById(R.id.albumArt);
// Hide both the navigation and status bar (immersive).
ViewManager.setFullscreenImmersive(getWindow());
List<MediaStream> mediaStreams = FirebaseManager.getMediaStreams(this);
System.out.print(mediaStreams);
}
All I want to do is retrieve the data from firebase. This is the database.
Any help would be appreciated.

Try this to retrieve the data:
DatabaseReference reference = FirebaseDatabase.getInstance().getReference("streams");
reference.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot datas: dataSnapshot.getChildren()){
String hosts=datas.child("host").getValue().toString();
String medias=datas.child("media").getValue().toString();
String metadata=datas.child("metadata").getValue().toString();
String ports=datas.child("port").getValue().toString();
String protocol=datas.child("protocol").getValue().toString();
String steamname=datas.child("streamName").getValue().toString();
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
the datasnapshot is streams,you then will be able to iterate inside the child 0 and get the data

How can I add more parameters in Android Firebase database post?

I am currently using the Firebase github example to create an app where users register and can post "status updates." I am able to do that correctly, but now I would like to add more parameters, like user location (latitude and longitude), but I am not sure where I would place this at. I am not sure at what point everything that is going to be added is added. Here is my current code:
NewPostActivity:
private DatabaseReference mDatabase;
private EditText mTextField;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_new_post);
mDatabase = FirebaseDatabase.getInstance().getReference();
mTextField = (EditText) findViewById(R.id.postText);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fabSubmitPost);
assert fab != null;
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
submitPost();
}
});
}
private void submitPost() {
final String text = mTextField.getText().toString();
if (TextUtils.isEmpty(text)) {
mTextField.setError("Required");
return;
}
final String userId = getUid();
mDatabase.child("users").child(userId).addListenerForSingleValueEvent new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
User user = dataSnapshot.getValue(User.class);
if (user == null) {
Toast.makeText(NewPostActivity.this, "Could not fetch user", Toast.LENGTH_SHORT).show();
} else {
writeNewPost(userId, user.username, text);
}
finish();
}
#Override
public void onCancelled(DatabaseError databaseError) {
Toast.makeText(NewPostActivity.this, databaseError.toString(), Toast.LENGTH_SHORT).show();
}
});
}
private void writeNewPost(String userId, String username, String text) {
String key = mDatabase.child("posts").push().getKey();
Post post = new Post(userId, username, text);
Map<String, Object> postValues = post.toMap();
Map<String, Object> childUpdates = new HashMap<>();
childUpdates.put("/posts/" + key, postValues);
childUpdates.put("/user-posts/" + userId + key, postValues);
mDatabase.updateChildren(childUpdates);
}
and this is the post file:
public class Post {
public String uid;
public String author;
public String text;
public int likeCount = 0;
public Map<String, Boolean> likes = new HashMap<>();
public Post() {
}
public Post(String uid, String author, String text) {
this.uid = uid;
this.author = author;
this.text = text;
}
#Exclude
public Map<String, Object> toMap() {
HashMap<String, Object> result = new HashMap<>();
result.put("uid", uid);
result.put("author", author);
result.put("text", text);
result.put("likeCount", likeCount);
result.put("likes", likes);
return result;
}
}

In order to add Latitude & Longitude when you save a Post you can add both the parameters to your existing class, you will need to modify Post class constructor to add 2 more arguments like :
public double lat,lng;
public Post(String uid, String author, String text,double lat,double lng) {
this.uid = uid;
this.author = author;
this.text = text;
this.lat = lat;
this.lng = lng;
}
then in your toMap function you can add the parameters to result like :
result.put("lat", lat);
result.put("lng", lng);
So when you call the constructor in your writeNewPost function you can change this line :
Post post = new Post(userId, username, text);
to
Post post = new Post(userId, username, text, lat, lng);
now your new post will be posted alongwith with latitude and longitude
i am assuming that you already have the latitude and longitude with you
Update
As you want to see the Posts that are posted within a Location you have posted them, you can do something like this,
In the Firebase query where you are querying the posts you can add orderByChild and equalTofilter to compare with current latitude & Longitude,
and if you want filter them based on some distance then you will have to query all the posts and then compare them locally