I'm making a blog posting app. I need to display the posts with the name of the author and the time.
I'm adding the post to database at posts/uid/key This key is added by Firebase on pushing the values. I cannot set this key to a fixed value as each post has different name, time, and body.
Now while retrieving the data, I want to know how to get the data at posts/uid/key/
I'm using this loop to traverse all the children of posts/ But I cannot go further into the nesting as I don't know what the keys are
for (DataSnapshot postSnapshot: dataSnapshot.getChildren()) {
String uid = (String) postSnapshot.child("uid").getValue();
String body = (String) postSnapshot.child("body").getValue();
}
}
I'm attaching the above listener to this reference
mPostReference = FirebaseDatabase.getInstance().getReference().child("posts");
How do I get the children of the keys without getting what the keys are?
private DatabaseReference mPostReference;
mPostReference = FirebaseDatabase.getInstance().getReference()
.child("posts");
ValueEventListener postListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
// Get Post object and use the values to update the UI
for (DataSnapshot postSnapshot: dataSnapshot.getChildren()) {
String uid = (String) postSnapshot.child("uid").getValue();
String body = (String) postSnapshot.child("body").getValue();
Toast.makeText(getActivity(), body,
Toast.LENGTH_SHORT).show();
}
}
Exported JSON
{
"posts" : {
"-KTGou5X14D8pq1sxyhR" : {
"body" : "first post",
"timestamp" : 1475620339666,
"uid" : "tmFt3NbcnLVlkrWQrIx1"
},
"-KTGp3mfM4krbGoTMZ8t" : {
"body" : "second post",
"likeCount" : 0,
"uid" : "tmFt3NbiwLVlkrWQrIx1"
}
}
}
Related
that's my database
{
"users" : {
"-MdgDcU3Zb-TiLlTwfwU" : {
"email" : "t1#email.com",
"fname" : "test",
"lname" : "1",
"password" : "t1",
"phoneno" : "304*******"
},
"-MdgNDN23XCTyB4DsF4W" : {
"email" : "t2#email.com",
"fname" : "test",
"lname" : "2",
"password" : "t2",
"phoneno" : "333*******"
}
}
}
that's the login activity's code
DatabaseReference reference= FirebaseDatabase.getInstance().getReference("users");
Query checkUser = reference.orderByChild("phoneno").equalTo(userphoneno);
checkUser.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot snapshot) {
if(snapshot.exists()){
//editTextphoneno.setError(null);
//editTextphoneno.setErrorEnabled(false);
String passwordFromDB =snapshot.child(userphoneno).child("password").getValue(String.class);
if(passwordFromDB.equals(userpassword)){
//editTextphoneno.setError(null);
//editTextphoneno.setErrorEnabled(false);
Intent i = new Intent(Login_page.this, Bottomnav.class);
startActivity(i);
finish();
}else{
editTextpassword.setError("Invalid Password");
editTextpassword.requestFocus();
}
}else{
editTextphoneno.setError("Invalid Phone Number");
editTextphoneno.requestFocus();
}
}
I want the user to login through his phone number and password but every time, after entering phone no and password I click on login, the app crashes. What I have understood is that may be the user's phone number and password is not being retrieved successfully.
When you are using the following query:
DatabaseReference reference= FirebaseDatabase.getInstance().getReference("users");
Query checkUser = reference.orderByChild("phoneno").equalTo(userphoneno);
It means that you are searching the "users" node, for all users who have the "phoneno" equal to "userphoneno". This also means that such a query may potentially return multiple results. Even if the query returns a single result, you'll need to loop through the DataSnapshot object using getChildren() method, as in the following lines of code:
checkUser.get().addOnCompleteListener(new OnCompleteListener<DataSnapshot>() {
#Override
public void onComplete(#NonNull Task<DataSnapshot> task) {
if (task.isSuccessful()) {
for (DataSnapshot ds : task.getResult().getChildren()) {
String passwordFromDB = ds.child("password").getValue(String.class);
Log.d("TAG", passwordFromDB);
//Add your logic
}
} else {
Log.d("TAG", task.getException().getMessage()); //Don't ignore potential errors!
}
}
});
Please see that inside onComplete, in order to get the password, there is no need for a .child(userphoneno) call, as the "password" is already a child of the DataSnapshot object.
More important, never store sensitive data as passwords in plain text. Malicious users might take advantage of that. Use Firebase Authentication for that and secure the database using Firestore Security Rules.
I want to retrieve only that post where postCategory matches the user interest.
How can I achieve this type of query. Any Help??
Below is my json file of database..
"Posts" : {
"-MAKobGjdhMfJFwZ1kol" : {
"postCategory" : "Animals",
"postDesc" : "still",
"postImage" : "Image Link",
"postPersonName" : "Name",
"postPersonUid" : "CLQA22uZpLS1ErIrnoBTrC3xqBw2",
"postTitle" : "ek"
},
"Users" : {
"CLQA22uZpLS1ErIrnoBTrC3xqBw2" : {
"email" : "email",
"interest" : {
"-MA14zFcNfs1JAjux129" : {
"name" : "Developer"
},
"-MA14zFgzhL-MOBB7D6h" : {
"name" : "Shopping"
}
},
"name" : "Name",
"uid" : "CLQA22uZpLS1ErIrnoBTrC3xqBw2"
}
In firebase database you cannot have such queries.
You should use Firestore (https://firebase.google.com/docs/firestore) for such advanced queries.
firestore/query-data
firestore
To get all posts with postCategory equal to Animals, you'd do:
DatabaseReference ref = FirebaseDatabase.getInstance().getReference("Posts");
Query query = ref.orderBy("postCategory").equalTo("Animals");
query.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot postSnapshot: dataSnapshot.getChildren()) {
Log.i(TAG, postSnapshot.getKey()+": "+postSnapshot.child("postTitle").getValue(String.class));
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
throw databaseError.toException();
}
}
If you want to retrieve posts for multiple categories, you'll have to perform a separate query for each of those and merge the results on your client.
I'd also recommend changing how you store the categories for a user. The idiomatic way is:
"Users" : {
"CLQA22uZpLS1ErIrnoBTrC3xqBw2" : {
"email" : "email",
"interest" : {
"Developer": true,
"Shopping": true
}
},
The reasons this is more common is that it automatically ensures that each value can occur only once in the interest object, since property names are by definition unique.
I have converted to Firebase for my Android development as I want to utilise the many features of Firebase (Notifications, Messaging, Storage etc), however, I am having difficulty receiving data from Firebase and cannot find detailed information online. Yes, I have tried the documentation but it does not explain the events I am experiencing.
I want to retrieve all the data that I have an insert it into an arraylist of objects. Here is a static example:
users[i] = new User("James" + (i*2.5), "Hmack00" + (i*2), "https://firebasPic_2019.03.03.05.26.35.jpg.jpg?alt=media&token=cf", "United Kingdom");
Database:
{
"Users" : {
"4PdlTlv3qjZ3BmDvrJyUut9Fnq43" : {
"Country" : "xx",
"Fullname" : "hh",
"ProfilePicture" : "htm/o/Images%2FSearchAdapter%2F4PdlTlv3qjZ3BmDvrJyUut9Fnq43%2FProfilePicture%2FProfilePic_2019.03.06.10.47.54.jpg.jpg?alt=media&token=b647708e-c6d5-4b45-bef0-3dc40301b73a",
"Username" : "hmack001"
},
"COg4r4io9hezhFpmK3adPucUXA93" : {
"Country" : "spain",
"Fullname" : "nat",
"ProfilePicture" : "hcom/o/Images%2FSearchAdapter%2FCOg4r4io9hezhFpmK3adPucUXA93%2FProfilePicture%2FProfilePic_2019.03.06.19.14.17.jpg.jpg?alt=media&token=8620b321-5cef-42f0-a828-dbb7c37c8e7d",
"Username" : "nat"
},
"Tw1xRxViygNsLqrQiaaMAvAduIu1" : {
"Country" : "uk",
"Fullname" : "harvey\n",
"ProfilePicture" : "t.com/o/Images%2FUsers%2FTw1xRxViygNsLqrQiaaMAvAduIu1%2FProfilePicture%2FProfilePic_2019.03.03.05.26.35.jpg.jpg?alt=media&token=c290e75a-5f92-4271-bcb5-c644fe1b14ef",
"Username" : "RGB"
},
"vOxr1RoDqgWogKK1lp9pfpTHc6w2" : {
"Country" : "scotland ",
"Fullname" : "greg greg",
"ProfilePicture" : "ot.com/o/Images%2FSearchAdapter%2FvOxr1RoDqgWogKK1lp9pfpTHc6w2%2FProfilePicture%2FProfilePic_2019.03.04.12.30.22.jpg.jpg?alt=media&token=27b024cf-0691-4121-8a27-26acf101ebc2",
"Username" : "greg"
},
"xecUOPeyMcQaQrgkU9ouDgK90Ai1" : {
"Country" : "ggh",
"Fullname" : "Da apply ",
"ProfilePicture" : "2FProfilePic_2019.03.03.04.58.50.jpg.jpg?alt=media&token=f35854c2-3ff9-4d18-9f7a-10c13f066c68",
"Username" : "gg"
}
}
}
Here is my code and I will explain my errors after (I have left in 'zombie' code, to show the attempts that I have made)
//Firebase Variables
private FirebaseDatabase mFirebaseDatabase;
private FirebaseAuth mAuth;
private FirebaseAuth.AuthStateListener mAuthListener;
private DatabaseReference myRef;
//Firebase Data
mAuth = FirebaseAuth.getInstance();
mFirebaseDatabase = FirebaseDatabase.getInstance();
userId = mAuth.getCurrentUser().getUid();
myRef = mFirebaseDatabase.getReference().child("Users").child(userId);
//Firebase Data
myRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) { //Function called every time a change is made to the database
showData(dataSnapshot);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) { //Function called when there is an error in the database/ with the call
Log.d("Print","Cancelled Firebase: " + databaseError.toString());
}
});
}
private void showData(DataSnapshot dataSnapshot) {
int userCount = 5;
int i = 0;
for (DataSnapshot ds : dataSnapshot.getChildren()) {
//User user = new User();
//User user = new User(); //Get Count of Firebase Users
//user = new User();
if (ds.child(userId).exists()) {
/*user.setFullname(ds.child(userId).getValue(User.class).getFullname()); //set the full name
user.setUsername(ds.child(userId).getValue(User.class).getUsername()); //set the username
user.setProfilePicture(ds.child(userId).getValue(User.class).getProfilePicture()); //set the profile picture
//Display Information
Log.d("DataSnapchat Test", "ShowData Name: " + user.getFullname());
Log.d("DataSnapchat Test", "ShowData Username: " + user.getUsername());
Log.d("DataSnapchat Test", "ShowData Picture: " + user.getProfilePicture());
ArrayList<String> userArrayList = new ArrayList<>();
userArrayList.add(user.getFullname());
userArrayList.add(user.getUsername());
userArrayList.add(user.getProfilePicture());
*/
String fullname = (String) ds.child(userId).child("Fullname").getValue();
Toast.makeText(this, "Fullname: " + fullname, Toast.LENGTH_SHORT).show();
//UserListAdapter adapter = new UserListAdapter(this, R.layout.find_profiles_search, userArrayList, mProfileSearch);
//mListView.setAdapter(adapter);
i++;
}
}
}
When I debug the code the showData function is never called and neither functions within the Value Event Listener are called, is this an Async Problem?
Currently I am trying to fetch data and insert it into a variable (Literally any data, once I have a working query I can convert it to fit by manipulating child fields etc).
Question: Does the addValueListener only work when data is changed in the database? If so then what is the alternative, if not then why are the functions not operating.
I do not recieve any errors and nothing is logged to the console.
I want to put my database into an array list, I know that I shouldnt use getChildren to do this, put I am trying to test if I can get any data before I try and get all the data.
You have some really weird loops in showData(). Since you're attaching a ValueEventListener to the node of the specific user, you can just look up the property values for that specific user:
myRef = mFirebaseDatabase.getReference().child("Users").child(userId);
myRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
Log.d("OnDataChange", dataSnapshot.getKey());
Log.d("OnDataChange", dataSnapshot.child("Fullname").getValue(String.class));
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Log.d("Print","Cancelled Firebase: " + databaseError.toString());
}
});
With the following code, I have the "history node".
History Node
{
"History" : {
"-LJANnl9ofbXlxLGxTGg" : {
"destination" : "3 Paradise Row",
"driver" : "ReGqRl2IIUhmLIqdBqBIELHBsgE3",
"location" : "1 Union St",
"payment response" : "approved",
"rating" : 0,
"ridePrice" : 5.25,
"rider" : "l3PPyBQux7YJhGGTdexxwDBteLM2",
"riderPaid" : "true",
"status" : "accepted",
"timestamp" : 1533494377
}
}
With the following code, I am trying to update "status" value to update from "accepted" to "arrived_loc". When I run the code, I have a yellow highlight in firebase but keeps the value of status "accepted".
update status to "arrived_loc"
driverId = FirebaseAuth.getInstance().getCurrentUser().getUid();
final DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
Query query = rootRefchild("History").orderByChild("driver").equalTo(driverId);
query.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
DataSnapshot nodeDS = dataSnapshot.getChildren().iterator().next();
String key = nodeDS.getKey();
Log.e(TAG, "key = " + key);
String path = "/" + dataSnapshot.getKey() + "/" + key;
Log.e(TAG, "path = " + path);
HashMap<String, Object> update = new HashMap<>();
update.put("status", "arrived_loc");
rootRef.child(path).updateChildren(update);
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
What am I doing wrong?
Edit #1
If I run this code:
DatabaseReference arrivedLoc = FirebaseDatabase.getInstance().getReference("History");
String historyId = arrivedLoc.push().getKey();
arrivedLoc.child(historyId).child("status").setValue("arrived at pickup");
I get an extra history node and no update:
"History" : {
"-LJAVN2iAWfRREdlBevb" : {
"destination" : "3 Union St",
"driver" : "ReGqRl2IIUhmLIqdBqBIELHBsgE3",
"location" : "123 Main Street",
"payment response" : "approved",
"rating" : 0,
"ridePrice" : 5.38,
"rider" : "l3PPyBQux7YJhGGTdexxwDBteLM2",
"riderPaid" : "true",
"status" : "accepted",
"timestamp" : 1533496391
},
"-LJAVaFd3Gzq3iIZGHeP" : {
"payment response" : "approved",
"riderPaid" : "true",
"status" : "accepted"
}
}
Edit #2 - image of database frozen
Edit #3
I can't seem to get it working for some reason so I renamed "status" to be "requestStatus" and created a new variable called rideStatus like:
status = "arrived at pickup";
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference().child("History");
rootRef.child(requestId).child("rideStatus").setValue(status);
This seems to work for now, but when I need to change the value of rideStatus, hopefully it will work.
Try with this code without push() function:
DatabaseReference arrivedLoc = FirebaseDatabase.getInstance().getReference("History");
String historyId = arrivedLoc.getKey();
arrivedLoc.child(historyId).child("status").setValue("arrived at pickup");
(depends on what you need to achieve on your app, might be a little different)
Update #2:
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference().child("History");
addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if(dataSnapshot.exists()){
for(DataSnapshot snapshot : dataSnapshot.getChildren()){
snapshot.getRef().child("status").setValue("arrived at pickup");
}
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
Try with updateChildren():
driverId = FirebaseAuth.getInstance().getCurrentUser().getUid();
HashMap<String, String> newData = new HashMap<>();
newData.put("status", "arrived_loc");
final DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference().child("History/" + driverId); // Or however the path is
rootRef.updateChildren(newData);
Why is the list I retrieve from the Firebase Database not ordered with orderByKey()?
DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference();
transactions = mDatabase.child("balance").child("users").child(userid).child("log").orderByKey();
transactions.addValueEventListener(new ValueEventListener() {
public void onDataChange(DataSnapshot snapshot) {
Map<String, Object> td = (HashMap<String,Object>) snapshot.getValue();
ArrayList<Object> values = new ArrayList<Object>();
values.addAll(td.values());
Log.d("Transactions", values.toString());
}
public void onCancelled(DatabaseError databaseError) {
Log.w(TAG, "loadPost:onCancelled", databaseError.toException());
// ...
}
});
The ArrayList "values" is unordered.
This is an example of the structure in json format:
"balance" : {
"users" : {
"log" : {
"-Kp0plO6zBeulHQ8S1Fj" : {
"In" : 100
},
"-Kp0qHM73Mcwbli1gaK6" : {
"Out" : -100
},
"-Kp0qgkORJx5sTi2rUZf" : {
"In" : 100
},
"-Kp1OCdSpUA7SEZhVoPR" : {
"In" : 100
},
"-Kp1OdtuuF6z_zlNj2St" : {
"In" : 100
}
}
}
}
When you retrieve a collection from Firebase, it receives three pieces of information for each child node:
the key of the child
the value of the child
the relative order of the child
When you call snapshot.getValue() in your current code, you tell Firebase to convert this into a Map<String, Object>. Since a Map is unordered, the Firebase client keeps the keys and values but loses the ordering of the children.
To ensure you keep the order, you must use DataSnapshot.getChildren() to process the result:
DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference();
transactions = mDatabase.child("balance").child("users").child(userid).child("log").orderByKey();
transactions.addValueEventListener(new ValueEventListener() {
public void onDataChange(DataSnapshot snapshot) {
ArrayList<Object> values = new ArrayList<Object>();
for (DataSnapshot child: snapshot.getChildren)) {
values.addAll(child.getValue());
}
}
To achieve what you want you need to change this line of code:
transactions = mDatabase.child("balance").child("users").child(userid).child("log").orderByKey();
with
transactions = mDatabase.child("balance").child("users").child(userid).child("log").orderByChild("In");