realtime database child won't showing because permission denied

i want to create child name 'Posts' in addpostactivity by adding data to the firebase. my application running well, it also shows " uploaded successfully ". it just that in my database there's nothing added with the data i already input from my app. i upload image while create the data it's successfully stored in storage firebase, but in realtime database, there's still nothing showing the added data even the 'Posts' child it self

my logchat shows this line.

2023-02-08 12:07:36.353 16589-16674/com.isjieman.ocion W/RepoOperation: updateChildren at /Posts/-NNjQ5njDqkVSZYUIZ-V failed: DatabaseError: Permission denied
2023-02-08 12:07:41.351 16589-16653/com.isjieman.ocion V/FA: Inactivity, disconnecting from the service 

here's my database security rules

{
  "rules": {
    "User" : {
      "$uid" : {
        ".read" : "$uid === auth.uid",
        ".write" : "$uid === auth.uid",
      }
    }
  }
}

and here's the database structure.

{
  "User": {
    "6FzpJ2sQC9gewbUIGHB8hiNWK1z2": {
      "background_image": "https://firebasestorage.googleapis.com/v0/b/final-project-idn.appspot.com/o/Default%20Images%2Fimg_background.png?alt=media&token=b51e7cf5-2015-4cc4-9583-159373d081e2",
      "bio": "Member of NCT",
      "email": "mark@gmail.com",
      "link": "",
      "profile_image": "https://firebasestorage.googleapis.com/v0/b/final-project-idn.appspot.com/o/Profile%20Pictures%2F6FzpJ2sQC9gewbUIGHB8hiNWK1z2.jpg?alt=media&token=17d71d89-353d-44fa-8f06-e33716de0611",
      "uid": "6FzpJ2sQC9gewbUIGHB8hiNWK1z2",
      "userName": "marklee"
    }
  }
}

i think it's because of my database security. but i don't really know about how should i change the rules safely.

here's my AddPostActivity.kt

class AddPostActivity : AppCompatActivity(), View.OnClickListener {
private lateinit var firebaseUser: FirebaseUser
private lateinit var addPostBinding: ActivityAddPostBinding
private var checker = ""
private var myUrl = ""
private var imageUri: Uri? = null
private var storagePostImageRef: StorageReference? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
addPostBinding = ActivityAddPostBinding.inflate(layoutInflater)
setContentView(addPostBinding.root)
supportActionBar?.hide()
//Dropdown item adapter
val itemCategory = listOf("Art", "Writing", "Application", "Design")
val adapterCategory = ArrayAdapter(this, R.layout.item_dropdown, itemCategory)
addPostBinding.acChooseCategory.setAdapter(adapterCategory)
val itemPriceRange = listOf("Rp 0 - 10.000", "Rp 10.000 - 50.000", "Rp 50.000 - 100.000")
val adapterPriceRange = ArrayAdapter(this, R.layout.item_dropdown, itemPriceRange)
addPostBinding.acPriceRange.setAdapter(adapterPriceRange)
firebaseUser = FirebaseAuth.getInstance().currentUser!!
storagePostImageRef = FirebaseStorage.getInstance().reference.child("Posts Pictures")
addPostBinding.btnAddImage.setOnClickListener(this)
addPostBinding.btnSavePost.setOnClickListener(this)
}
override fun onClick(v: View) {
when(v.id){
R.id.btnAddImage -> addImagePost()
R.id.btnSavePost -> savePost()
}
}
private fun savePost() {
if (checker == "clicked")
{
uploadPostWithImage()
}
else
{
uploadPost()
}
}
private fun uploadPost() {
when{
TextUtils.isEmpty(addPostBinding.etTitlePost.text.toString()) -> Toast.makeText(this, "Please add Title Post.", Toast.LENGTH_LONG).show()
TextUtils.isEmpty(addPostBinding.etDescPost.text.toString()) -> Toast.makeText(this, "Please add Description.", Toast.LENGTH_LONG).show()
TextUtils.isEmpty(addPostBinding.acChooseCategory.text.toString()) -> Toast.makeText(this, "Please Choose Category.", Toast.LENGTH_LONG).show()
TextUtils.isEmpty(addPostBinding.acPriceRange.text.toString()) -> Toast.makeText(this, "Please Choose Price Range.", Toast.LENGTH_LONG).show()
TextUtils.isEmpty(addPostBinding.etDurationPost.text.toString()) -> Toast.makeText(this, "Please add Duration Time.", Toast.LENGTH_LONG).show()
TextUtils.isEmpty(addPostBinding.etPaymentMethods.text.toString()) -> Toast.makeText(this, "Please add Payment Methods.", Toast.LENGTH_LONG).show()
else -> {
val ref = FirebaseDatabase.getInstance().reference.child("Posts")
val postId = ref.push().key
val postMap = HashMap<String, Any>()
postMap["postId"] = postId!!
postMap["title"] = addPostBinding.etTitlePost.text.toString()
postMap["description"] = addPostBinding.etDescPost.text.toString()
postMap["category"] = addPostBinding.acChooseCategory.text.toString()
postMap["priceRange"] = addPostBinding.acPriceRange.text.toString()
postMap["duration"] = addPostBinding.etDurationPost.text.toString()
postMap["paymentMethods"] = addPostBinding.etPaymentMethods.text.toString()
postMap["publisher"] = FirebaseAuth.getInstance().currentUser!!.uid
ref.child(postId).updateChildren(postMap)
Toast.makeText(this, "Post Uploaded successfully.", Toast.LENGTH_LONG).show()
val intent = Intent(this, MainActivity::class.java)
startActivity(intent)
finish()
}
}
}
private fun uploadPostWithImage() {
when{
imageUri == null -> Toast.makeText(this, "Please select image first.", Toast.LENGTH_LONG).show()
TextUtils.isEmpty(addPostBinding.etTitlePost.text.toString()) -> Toast.makeText(this, "Please add Title Post.", Toast.LENGTH_LONG).show()
TextUtils.isEmpty(addPostBinding.etDescPost.text.toString()) -> Toast.makeText(this, "Please add Description.", Toast.LENGTH_LONG).show()
TextUtils.isEmpty(addPostBinding.acChooseCategory.text.toString()) -> Toast.makeText(this, "Please Choose Category.", Toast.LENGTH_LONG).show()
TextUtils.isEmpty(addPostBinding.acPriceRange.text.toString()) -> Toast.makeText(this, "Please Choose Price Range.", Toast.LENGTH_LONG).show()
TextUtils.isEmpty(addPostBinding.etDurationPost.text.toString()) -> Toast.makeText(this, "Please add Duration Time.", Toast.LENGTH_LONG).show()
TextUtils.isEmpty(addPostBinding.etPaymentMethods.text.toString()) -> Toast.makeText(this, "Please add Payment Methods.", Toast.LENGTH_LONG).show()
else -> {
val progressDialog = ProgressDialog(this)
progressDialog.setTitle("Adding New Post")
progressDialog.setMessage("Please wait, we are Uploading your Post...")
progressDialog.show()
val fileRef = storagePostImageRef!!.child(System.currentTimeMillis().toString() + ".jpg")
val uploadTask: StorageTask<*>
uploadTask = fileRef.putFile(imageUri!!)
uploadTask.continueWithTask(Continuation <UploadTask.TaskSnapshot, Task<Uri>>{ task ->
if (!task.isSuccessful)
{
task.exception?.let {
throw it
progressDialog.dismiss()
}
}
return@Continuation fileRef.downloadUrl
}).addOnCompleteListener (OnCompleteListener<Uri> { task ->
if (task.isSuccessful)
{
val downloadUrl = task.result
myUrl = downloadUrl.toString()
val ref = FirebaseDatabase.getInstance().reference.child("Posts")
val postId = ref.push().key
val postMap = HashMap<String, Any>()
postMap["postId"] = postId!!
postMap["title"] = addPostBinding.etTitlePost.text.toString()
postMap["description"] = addPostBinding.etDescPost.text.toString()
postMap["category"] = addPostBinding.acChooseCategory.text.toString()
postMap["priceRange"] = addPostBinding.acPriceRange.text.toString()
postMap["duration"] = addPostBinding.etDurationPost.text.toString()
postMap["paymentMethods"] = addPostBinding.etPaymentMethods.text.toString()
postMap["post_image"] = myUrl
postMap["publisher"] = FirebaseAuth.getInstance().currentUser!!.uid
ref.child(postId).updateChildren(postMap)
Toast.makeText(this, "Post Uploaded successfully.", Toast.LENGTH_LONG).show()
val intent = Intent(this, MainActivity::class.java)
startActivity(intent)
finish()
progressDialog.dismiss()
}
else
{
progressDialog.dismiss()
}
})
}
}
}
private fun addImagePost() {
checker = "clicked"
CropImage.activity()
.setAspectRatio(2, 1)
.start(this)
}
override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
super.onActivityResult(requestCode, resultCode, data)
if (requestCode == CropImage.CROP_IMAGE_ACTIVITY_REQUEST_CODE  &&  resultCode == Activity.RESULT_OK  &&  data != null)
{
val result = CropImage.getActivityResult(data)
imageUri = result.uri
addPostBinding.btnAddImage.setImageURI(imageUri)
}
}
}

Add rules for posts too.

{
"rules": {
"User" : {
"$uid" : {
".read" : "$uid === auth.uid",
".write" : "$uid === auth.uid",
}
}
"Posts" : {
"$uid" : {
".read" : "$uid === auth.uid",
".write" : "$uid === auth.uid",
}
}
}
}