Android: How to Upload an image on Firebase storage?

package org.geeksforgeeks.demo;

import android.app.ProgressDialog;
import android.graphics.*;
import android.net.Uri;
import android.os.Bundle;
import android.widget.*;
import androidx.activity.result.ActivityResultLauncher;
import androidx.activity.result.contract.ActivityResultContracts;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import com.google.firebase.ktx.Firebase;
import com.google.firebase.storage.*;

import java.io.InputStream;
import java.util.UUID;

public class MainActivity extends AppCompatActivity {

    // Declare UI components
    private Button btnSelect;
    private Button btnUpload;
    private ImageView imageView;

    // Store the URI of the selected image
    private Uri filePath;

    // Firebase Storage instance
    private FirebaseStorage storage;

    // Reference to the Firebase Storage root directory
    private StorageReference storageReference;

    // Launcher to handle image picking from gallery
    private ActivityResultLauncher<String> imagePickerLauncher;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // Bind UI elements to layout views
        btnSelect = findViewById(R.id.btnChoose);
        btnUpload = findViewById(R.id.btnUpload);
        imageView = findViewById(R.id.imgView);

        // Initialize Firebase Storage
        storage = StorageKt.getStorage(Firebase.INSTANCE);
        storageReference = storage.getReference();

        // Initialize image picker with activity result contract
        imagePickerLauncher = registerForActivityResult(
                new ActivityResultContracts.GetContent(),
                uri -> {
                    // Handle the result from the image picker
                    if (uri != null) {
                        filePath = uri;
                        try {
                            // Open input stream from the selected image URI
                            InputStream inputStream = getContentResolver().openInputStream(uri);

                            // Decode input stream into a Bitmap and display in ImageView
                            Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
                            imageView.setImageBitmap(bitmap);
                        } catch (Exception e) {
                            // Handle any exceptions during image decoding
                            e.printStackTrace();
                            Toast.makeText(MainActivity.this, "Failed to load image", Toast.LENGTH_SHORT).show();
                        }
                    }
                });

        // Set click listener to launch image picker
        btnSelect.setOnClickListener(v -> imagePickerLauncher.launch("image/*"));

        // Set click listener to upload the selected image
        btnUpload.setOnClickListener(v -> uploadImage());
    }

    // Function to upload selected image to Firebase Storage
    private void uploadImage() {
        // Check if an image has been selected
        if (filePath != null) {
            // Create and show a progress dialog during upload
            ProgressDialog progressDialog = new ProgressDialog(this);
            progressDialog.setTitle("Uploading...");
            progressDialog.show();

            // Create a unique path under 'images/' using UUID
            StorageReference ref = storageReference.child("images/" + UUID.randomUUID().toString());

            // Upload the file to Firebase Storage
            ref.putFile(filePath)
                .addOnSuccessListener(taskSnapshot -> {
                    // Dismiss the dialog and show success message
                    progressDialog.dismiss();
                    Toast.makeText(MainActivity.this, "Image Uploaded!!", Toast.LENGTH_SHORT).show();
                })
                .addOnFailureListener(e -> {
                    // Dismiss the dialog and show failure message
                    progressDialog.dismiss();
                    Toast.makeText(MainActivity.this, "Upload Failed: " + e.getMessage(), Toast.LENGTH_SHORT).show();
                })
                .addOnProgressListener(taskSnapshot -> {
                    // Calculate and update progress percentage in the dialog
                    double progress = (100.0 * taskSnapshot.getBytesTransferred() / taskSnapshot.getTotalByteCount());
                    progressDialog.setMessage("Uploaded " + (int) progress + "%");
                });
        } else {
            // Show message if no image is selected
            Toast.makeText(this, "No image selected!", Toast.LENGTH_SHORT).show();
        }
    }
}