How to retrieve data child of child from firebase / Android - java

Here is my firebase database
Here is the info.class
Here is the insert
I want to get all the data from firebase to List View
How can i get all data under "information" data list ?
please help
db = FirebaseDatabase.getInstance();
ref = db.getReference("infomation");
protected void onStart() {
super.onStart();
ref.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
infoList.clear();
for (DataSnapshot infoSnapshot : dataSnapshot.getChildren()){
info info = infoSnapshot.getValue(info.class);
infoList.add(info);
}
InfoList adapter = new InfoList(Welcome.this, infoList);
listViewInfo.setAdapter(adapter);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}


In your insertion part, you need to change it like below,
DatabaseReference ref = FirebaseDatabase.getInstance().getReference("information");
ref.child( FirebaseAuth.getInstance().getCurrentUser().getUid()).setValue(in);
but if you want to save data like save the data like
information >uid> random value > then the data
that use change data retrieving part like below
for (DataSnapshot infoSnapshot : dataSnapshot.getChildren().getChildren()){
info info = infoSnapshot.getValue(info.class);
infoList.add(info);
}

Related

Android: Notify on specific value change in Firebase real-time database

Following is screenshot of my Firebase realtime database. How can I notify a user whenever the item worker_id is changed?
I've tried the following code, but it notifies about each type of data change. I want notification specific to change in worker_id:
private void CheckDataChange(){
FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference myRef = database.getReference("posts");
Query query = myRef.orderByChild("workType");
ValueEventListener valueEventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
Log.d("Firebase","onDatachange");
for(DataSnapshot ds : dataSnapshot.getChildren()) {
try {
if(!ds.child("worker_id").getValue(String.class).equals("0")) {
Toast.makeText(MainActivity.this, "Request accepted", Toast.LENGTH_SHORT).show();
}
}catch (Exception ex){
Log.e("Firebase",ex.getMessage()+ex.getCause());
}
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Log.d("Firebase", databaseError.getMessage());
}
};
query.addValueEventListener(valueEventListener);
}

There is nothing built into Firebase to raise an event only when the worker_id in your current structure changes.
The most common way to implement something like that would be to create a map mapping ds.getKey() to the value of worker_id when onDataChange is first called, and then comparing the value you get against that for any updates.

Duplicate child when i call push() in Firebase Realtime Database

I am trying to retrieve data from Firebase Realtime Database and add this data to a listview. When I call push() firebase generates two children (one inside the other) with the same unique key. This is the structure of my database:
database
That is how I save the data:
RunningSession runningSession = new RunningSession(date, activityTime, pace, timeElapsed,
finalDistance, image, tipe);
DatabaseReference reference = databaseReference.child("users").child(userUid).child("activities").push();
Map<String, Object> map = new HashMap<>();
map.put(reference.getKey(),runningSession);
reference.updateChildren(map);
This is how i retrieve the data (results in a null pointer exception):
DatabaseReference reference = databaseReference.child("users").child(userId).child("activities");
reference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot snapshot) {
list.clear();
for (DataSnapshot snpshot : snapshot.getChildren()) {
RunningSession run = snpshot.getValue(RunningSession.class);
list.add(run);
}
}
#Override
public void onCancelled(#NonNull DatabaseError error) {
}
});
ListViewAdapter adapter = new ListViewAdapter(this, list);
ListView activityItems = (ListView) findViewById(R.id.activityList);
activityItems.setAdapter(adapter);

You are getting duplicate push IDs because you are adding them twice to your reference. If you only need one, then simply use the following lines of code:
RunningSession runningSession = new RunningSession(date, activityTime, pace, timeElapsed, finalDistance, image, tipe);
DatabaseReference reference = databaseReference.child("users").child(userUid).child("activities");
String pushedId = reference.push().getKey();
reference.child(pushedId).setValue(runningSession);
The code for reading that may remain unchanged.

Retrieve data from FireBase database in android, java by searchin with an ID

I tried to implement a code in java to retrieve data from database( firebase) by searching with an ID and show it in the form.
In here i have already saved some data and now when i type the id, it need to show the data of the id in this same form.
btnShow.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
searchID = txtid.getText().toString().trim();
DatabaseReference readRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference dref = readRef.child("Student");
Query query = dref.orderByChild("id").equalTo(searchID);
query.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
if(dataSnapshot.hasChildren()){
txtID.setText((dataSnapshot.child("id").getValue().toString()));
txtName.setText((dataSnapshot.child("name").getValue().toString()));
txtAdd.setText((dataSnapshot.child("address").getValue().toString()));
txtConNo.setText((dataSnapshot.child("conNo").getValue().toString()));
}
else
Toast.makeText(getApplicationContext(),"No Source to Display",Toast.LENGTH_SHORT).show();
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
});
This is the java code i implemented to do that. But when i run the program and give the correct id in database it is always showing as "No source to display"( There are data in my database and save function is working properly)
I am a beginner in android studio and firebase. Please modify the above code and tell me how can i search by ID.
Thankyou.

Try the following:
if(dataSnapshot.exists()){
for(DataSnapshot ds : dataSnapshot.getChildren()){
txtID.setText((ds.child("id").getValue().toString()));
txtName.setText((ds.child("name").getValue().toString()));
txtAdd.setText((ds.child("address").getValue().toString()));
txtConNo.setText((ds.child("conNo").getValue().toString()));
}
}
Your reference is at node Student therefore you need to loop and then use ds to access the attributes. Also, don't forget to check for errors inside onCancelled:
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Log.d("TAG", databaseError.getMessage()); //Don't ignore potential errors!
}

How Can I get The Child Id Of the Root Node In Firebase Realtime Database?

This is my RealTime Database JSON data. I want to fetch the child id of the root node Assets. but can't seem to figure out as I am not using userid instead I am scanning a barcode and saving the data under the particular barcode number.
Here's the Screenshot

To get those keys, please use the following lines of code:
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference assetsRef = rootRef.child("Assets");
ValueEventListener valueEventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot ds : dataSnapshot.getChildren()) {
String key = ds.getKey();
Log.d(TAG, key);
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Log.d(TAG, databaseError.getMessage()); //Don't ignore errors!
}
};
assetsRef.addListenerForSingleValueEvent(valueEventListener);
The result in the logcat will be:
CFM100010254BG
GE123100010254GB
If you want only the first child (CFM100010254BG), instead of using a DatabaseReference, please use the following query:
Query query = assetsRef.orderByChuild("asset_model").equalTo("CFM56");
And attach the listener on this query.

Access all child values of a snapshot in firebase

This is my Firebase Realtime Database.
I want to read memberRollNo , and memberMobileNo of the node whose name(key) is equal to nname. I am only able to read memberRollNo with my code and Textview for memberMobileNo shows out to be blank.
DBRef = FirebaseDatabase.getInstance().getReference();
DBRef.child("Members").addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
String roll = dataSnapshot.child(nname).child("memberRollNo").getValue(String.class);
DRollNo.setText(roll);
String mob = dataSnapshot.child(nname).child("memberMobile").getValue(String.class);
DMobile.setText(mob);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
}
DRollNo and DMobile are textview.

Change this:
String mob = dataSnapshot.child(nname).child("memberMobile").getValue(String.class);
into this:
String mob = dataSnapshot.child(nname).child("memberPhone").getValue(String.class);
In your database, you do not have a child called memberMobile. The name inside the method child() needs to be the same as in the database to be able to retrieve it.

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