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how to update user profile image using firebase and Picasso library

I'm trying to update the user profile image in the Firebase Realtime Database on my application but I'm unable to get the reference of the current user as I declare it in another activity.
My code and database structure is as follows:
profile image
as in this current picture and the code, I'm writing manually the id of the child node (gli) because it is the user_name of the current user in the firebase, please help me how can I give it a path through coding.
code:
private void profileImage(){
pImageRef = FirebaseDatabase.getInstance().getReference("doctors/doctors_registration/gli/pimage"); 👈👈
pImageRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
String imageurl= String.valueOf(dataSnapshot.getValue()) ;
Toast.makeText(HomeActivity.this, "link:"+imageurl, Toast.LENGTH_SHORT).show();
Picasso.get()
.load(imageurl)
.into(profileimg);
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
Please see the screenshot of the database structure and help me how I can get the current user profile image?

First of all, stop ignoring errors. At a minimum, please add inside the onCancelled method:
Log.d(TAG, error.getMessage());
Please also note that Picasso is a library that can help you download images and not update them in the Realtime Database. If you want to update the image at an existing location, remember that there is no need to read it first. To solve this, please use the following line of code:
pImageRef.updateChildren("yourNewUrl");
You can also use in this case addOnCompleteListener() to see if something goes wrong.
If you however need to update the image right after you read it, then inside the onDataChange() method, use the following line of code:
dataSnapshot.getRef().updateChildren("yourNewUrl");

Reading Images from multiple nodes in Firebase

So I'm making a wallpaper app that has various categories but I want to display all images from all nodes in Firebase in one fragment called Random, I also want the Images to shuffle images from each parent node
The following is my Firebase structure :
There are also child nodes in them :
The following is my java code from my Random fragment :
private void getWallpapers() {
progressBar.setVisibility(View.VISIBLE);
myRef = database.getReference().child("Wallpaper").child("Random");
myRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
collectionsArray.clear();
for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
wallpaper z = postSnapshot.getValue(wallpaper.class);
collectionsArray.add(z);
}
Collections.reverse(collectionsArray);
progressBar.setVisibility(View.GONE);
mAdapter.notifyDataSetChanged();
}
#Override
public void onCancelled(DatabaseError error) {
// Failed to read value
System.out.println("Error Reading from DB");
}
});

There is no built-in query that can get elements across different nodes in the database. Seeing that you have different structures for each category, the best option I can think of is to duplicate the data. This practice is called denormalization and is a common practice when it comes to Firebase. For a better understanding, I recommend you see this video, Denormalization is normal with the Firebase Database.
So you should create another node that will hold all images you have in the database, no matter from which category belongs. To select a random wallpaper, please check my answer from the following post:
How to get unique random product in node Firebase?
Also remember, when you are duplicating data, there is one thing that you need to keep in mind. In the same way, you are adding data, you need to maintain it. In other words, if you want to update/delete a wallpaper, you need to do it in every place that it exists.
If you might also be interested in:
What is denormalization in Firebase Cloud Firestore?

Picasso IllegalArgumentException Target must not be null: Retrieve data from Firebase

I keep having this issue in my code.
From the code below, I think I already checked if the load() value is null. If it's null, the code should never reach Picasso.
My app allows users to give comments or upload photos to a dish (like yelp). However, they're not required to post both. So there could be data have only comment or photo.
So, I'm not sure if that's something that causes the problem.
This is the database where I wanna retrieve from:
https://ibb.co/ZNTSFb0
To explain my code a little:
Check if the dataSnapshot1 has image value;
if yes, then check if the dishName matches this dish;
if yes, then put the photo on the imageView.
Code:
mdatabaseReferece1 = FirebaseDatabase.getInstance().getReference("Post");
mdatabaseReferece1.addValueEventListener(new ValueEventListener() {
#Override
for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()){
if (dataSnapshot1.child("image").getValue()!=null){
if (dataSnapshot1.child("dishName").getValue().toString().equals(newDish)) {
ImageView imageView = findViewById(R.id.gallery_photo);
Picasso.get().load(dataSnapshot1.child("image").getValue().toString()).into(imageView);
gallery.addView(view);}
}
}
}
I don't have to use Picasso if there's any other easier way. All I want to have on my app is a list of matched photos retrieved from the firebase.

Change the following:
if(dataSnapshot1.child("image").getValue()!=null)
Into this:
if(dataSnapshot1.hasChild("image")){ /* code */ }
From the docs:
hasChild(String path)
Can be used to determine if this DataSnapshot has data at a particular location

Basic Read & Write with Firebase on Android

So I started learning Android, a coworker -who is a fresh grad- at where I'm interning adviced me to learn Firebase since it is free and easy to use. I'm trying to do the most basic Read and Write operations, but for some reason I cant do it. I searched many different articles but i couldn't find why. Even said coworker tried to help me but still...
I connected to Firebase, gave needed permissions etc. and Firebase statics shows one app connected to it.
I'm following Firebase's own documents but its own code doesn't work on my app.
Said code:
// Read from the database
myRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
// This method is called once with the initial value and again
// whenever data at this location is updated.
String value = dataSnapshot.getValue(String.class);
Log.d(TAG, "Value is: " + value);// "TAG" shows red
}
#Override
public void onCancelled(DatabaseError error) {
// Failed to read value
Log.w(TAG, "Failed to read value.", error.toException());
}
});
The thing I'm missing might be really simple. But like I said I looked into alot of articles. For start i just want to write something on database and read a string from it and print it on screen.
Edit: Compiler error I'm getting is : https://prnt.sc/kb7kcu (Too long to paste as text)
As if code not working, Firebase docs I'm following gives compiler error. And other codes from articles i tried doesn't update the database or read from it.

Hint -> paste this code and look closer how data is structured as a map of key value pairs.
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
Log.d(TAG, "dataSnapshot: " + String.valueOf(dataSnapshot));
for (DataSnapshot dataSnapshotItem : dataSnapshot.getChildren()) {
Log.d(TAG, "Inside: " + String.valueOf(dataSnapshotItem));
}
}

I this you was not define a rule in firebase console, so you have not access to read and write permission, for permission do follow steps :
Go to firebase console
select Database and click on realtime databse
in a tab manu you can see Rules tab, in the rules tab set rules like follow
{
"rules": {
".read": "auth == null",
".write": "auth == null"
}
}
check insertion or retrieve operation its work.

Simple way to retrieve image from firebase android

Since im new in Android coding i have one question, how just to retrieve images from folder from Firebase for Android? I did my search on topic but im too noob in this matter im asking this, I was following tuts on youtube nothing came in hand, can somebody help me with the code?

Assuming you are using Firebase Storage to host your images, in order to display a image from a folder to an ImageView, you can use one of the following libraries: Glide or Picasso.
If you want to display all the images within a folder, first you need to store them. In order to make it work, when you are uploading an image to Firebase Storage, store the corresponding url in Firebase database. Your database should look like this:
Firebase-root
|
--- images
|
--- imageUrl1: "https://..."
|
--- imageUrl2: "https://..."
In order to get all those url's, just attach a listener on the images node and get all the url's from the DataSnapshot object like this:
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference imagesRef = rootRef.child("images");
ValueEventListener valueEventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot ds : dataSnapshot.getChildren()) {
String url = ds.getValue(String.class);
Log.d("TAG", url);
}
}
#Override
public void onCancelled(DatabaseError databaseError) {}
};
imagesRef.addListenerForSingleValueEvent(valueEventListener);

Use Glide with FirebaseImageLoader.
compile 'com.github.bumptech.glide:glide:3.7.0'
Sample:
Glide.with(CONTEXT).using(new FirebaseImageLoader()).load(IMAGE_URL).into(IMAGE_VIEW);