my android app not uploading photo directly to Dropbox app folder using API

can you explain the steps to me i lost in the internet searching for a solution to my situation this is my code

package com.example.decamera;

import android.Manifest;
import android.content.pm.PackageManager;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.Typeface;
import android.location.Address;
import android.location.Geocoder;
import android.location.Location;
import android.os.Bundle;
import android.os.Environment;
import android.view.View;
import android.widget.ImageButton;
import android.widget.TextView;
import android.widget.Toast;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.camera.core.Camera;
import androidx.camera.core.CameraSelector;
import androidx.camera.core.ImageCapture;
import androidx.camera.core.ImageCaptureException;
import androidx.camera.core.Preview;
import androidx.camera.lifecycle.ProcessCameraProvider;
import androidx.camera.view.PreviewView;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;
import androidx.exifinterface.media.ExifInterface;
import androidx.lifecycle.LifecycleOwner;

import com.dropbox.core.DbxRequestConfig;
import com.dropbox.core.v2.DbxClientV2;
import com.dropbox.core.v2.files.WriteMode;
import com.google.android.gms.location.FusedLocationProviderClient;
import com.google.android.gms.location.LocationServices;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.common.util.concurrent.ListenableFuture;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.List;
import java.util.Locale;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private static final int CAMERA_PERMISSION_REQUEST = 100;
    private static final String[] REQUIRED_CAMERA_PERMISSIONS = new String[]{Manifest.permission.CAMERA};
    private static final String DROPBOX_ACCESS_TOKEN = "here should i input my access token but it changend everytime"; // Replace with your Dropbox access token

    private PreviewView previewView;
    private ImageCapture imageCapture;
    private TextView addressTextView;

    private ExecutorService cameraExecutor = Executors.newSingleThreadExecutor();
    private FusedLocationProviderClient fusedLocationProviderClient;
    private Geocoder geocoder;

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

        previewView = findViewById(R.id.previewView);
        ImageButton captureButton = findViewById(R.id.captureButton);
        addressTextView = findViewById(R.id.addressTextView);

        fusedLocationProviderClient = LocationServices.getFusedLocationProviderClient(this);
        geocoder = new Geocoder(this, Locale.getDefault());

        captureButton.setOnClickListener(this);

        if (allPermissionsGranted()) {
            startCamera();
            getLastLocation();
        } else {
            ActivityCompat.requestPermissions(this, REQUIRED_CAMERA_PERMISSIONS, CAMERA_PERMISSION_REQUEST);
        }
    }

    private void startCamera() {
        ListenableFuture<ProcessCameraProvider> cameraProviderFuture = ProcessCameraProvider.getInstance(this);

        cameraProviderFuture.addListener(() -> {
            try {
                ProcessCameraProvider cameraProvider = cameraProviderFuture.get();
                bindPreview(cameraProvider);

            } catch (Exception e) {
                e.printStackTrace();
            }
        }, ContextCompat.getMainExecutor(this));
    }

    private void bindPreview(ProcessCameraProvider cameraProvider) {
        Preview preview = new Preview.Builder().build();

        CameraSelector cameraSelector = new CameraSelector.Builder()
                .requireLensFacing(CameraSelector.LENS_FACING_BACK)
                .build();

        Camera camera = cameraProvider.bindToLifecycle((LifecycleOwner) this, cameraSelector, preview);

        preview.setSurfaceProvider(previewView.getSurfaceProvider());

        imageCapture = new ImageCapture.Builder()
                .setCaptureMode(ImageCapture.CAPTURE_MODE_MINIMIZE_LATENCY)
                .setTargetRotation(previewView.getDisplay().getRotation())
                .build();

        cameraProvider.unbindAll();
        cameraProvider.bindToLifecycle((LifecycleOwner) this, cameraSelector, preview, imageCapture);
    }

    private void getLastLocation() {
        if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED) {
            fusedLocationProviderClient.getLastLocation()
                    .addOnSuccessListener(this, new OnSuccessListener<Location>() {
                        @Override
                        public void onSuccess(Location location) {
                            if (location != null) {
                                updateAddress(location);
                            }
                        }
                    });
        } else {
            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, CAMERA_PERMISSION_REQUEST);
        }
    }

    private void updateAddress(Location location) {
        try {
            List<Address> addresses = geocoder.getFromLocation(location.getLatitude(), location.getLongitude(), 1);
            if (addresses != null && addresses.size() > 0) {
                Address address = addresses.get(0);
                String fullAddress = address.getAddressLine(0);
                addressTextView.setText(fullAddress);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void onClick(View v) {
        if (v.getId() == R.id.captureButton) {
            captureImage();
        }
    }

    private void captureImage() {
        File photoFile = createImageFile();
        if (photoFile != null) {
            ImageCapture.OutputFileOptions outputFileOptions =
                    new ImageCapture.OutputFileOptions.Builder(photoFile).build();

            imageCapture.takePicture(outputFileOptions, ContextCompat.getMainExecutor(this), new ImageCapture.OnImageSavedCallback() {
                @Override
                public void onImageSaved(@Nullable ImageCapture.OutputFileResults outputFileResults) {
                    combineImageWithAddress(photoFile, addressTextView.getText().toString());
                    uploadToDropbox(photoFile);  // Upload to Dropbox
                }

                @Override
                public void onError(@NonNull ImageCaptureException exception) {
                    runOnUiThread(() -> Toast.makeText(MainActivity.this, "Error capturing image: " + exception.getMessage(), Toast.LENGTH_SHORT).show());
                }
            });
        } else {
            runOnUiThread(() -> Toast.makeText(MainActivity.this, "Error creating photo file", Toast.LENGTH_SHORT).show());
        }
    }


    private void combineImageWithAddress(File photoFile, String addressText) {
        Bitmap photoBitmap = BitmapFactory.decodeFile(photoFile.getAbsolutePath());

        // Check the orientation of the image and rotate it if needed
        int rotation = getRotationAngle(photoFile.getAbsolutePath());
        if (rotation != 0) {
            photoBitmap = rotateBitmap(photoBitmap, rotation);
        }

        Bitmap combinedBitmap = photoBitmap.copy(photoBitmap.getConfig(), true);
        Canvas canvas = new Canvas(combinedBitmap);

        Paint paint = new Paint();
        paint.setColor(Color.WHITE);
        paint.setTextSize(150); // Adjust this value according to your preference
        paint.setAntiAlias(true);

        // Set the font to bold
        paint.setTypeface(Typeface.create(Typeface.DEFAULT, Typeface.BOLD));

        // Set the coordinates for the left bottom corner
        float x = 50;
        float y = combinedBitmap.getHeight() - 50;

        canvas.drawText(addressText, x, y, paint);

        saveCombinedImage(combinedBitmap, photoFile);
    }

    private int getRotationAngle(String imagePath) {
        ExifInterface exifInterface;
        try {
            exifInterface = new ExifInterface(imagePath);
        } catch (IOException e) {
            e.printStackTrace();
            return 0;
        }

        int orientation = exifInterface.getAttributeInt(ExifInterface.TAG_ORIENTATION, ExifInterface.ORIENTATION_NORMAL);

        switch (orientation) {
            case ExifInterface.ORIENTATION_ROTATE_90:
                return 90;
            case ExifInterface.ORIENTATION_ROTATE_180:
                return 180;
            case ExifInterface.ORIENTATION_ROTATE_270:
                return 270;
            default:
                return 0;
        }
    }

    private Bitmap rotateBitmap(Bitmap bitmap, int angle) {
        Matrix matrix = new Matrix();
        matrix.postRotate(angle);
        return Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, true);
    }

    private void saveCombinedImage(Bitmap combinedBitmap, File photoFile) {
        try {
            FileOutputStream out = new FileOutputStream(photoFile);
            combinedBitmap.compress(Bitmap.CompressFormat.JPEG, 100, out);
            out.flush();
            out.close();
        } catch (IOException e) {
            e.printStackTrace();
            runOnUiThread(() -> Toast.makeText(MainActivity.this, "Error combining image with address: " + e.getMessage(), Toast.LENGTH_SHORT).show());
        }
    }

    private void uploadToDropbox(File photoFile) {
        // Check if the file exists before attempting to upload
        if (photoFile == null || !photoFile.exists()) {
            runOnUiThread(() -> Toast.makeText(MainActivity.this, "Error: Photo file does not exist", Toast.LENGTH_SHORT).show());
            return;
        }

        // Set up Dropbox client
        DbxRequestConfig config = DbxRequestConfig.newBuilder("Decamera").build();
        DbxClientV2 client = new DbxClientV2(config, DROPBOX_ACCESS_TOKEN);

        try {
            // Specify the path in Dropbox where you want to upload the file
            String remotePath = "/Decamera/" + photoFile.getName();

            // Open the photo file for reading
            try (InputStream in = new FileInputStream(photoFile)) {
                // Upload the file to Dropbox
                client.files().uploadBuilder(remotePath)
                        .withMode(WriteMode.ADD)
                        .uploadAndFinish(in); // This line was missing

                // Display a success message
                runOnUiThread(() -> Toast.makeText(MainActivity.this, "Photo uploaded to Dropbox", Toast.LENGTH_SHORT).show());
            }

        } catch (Exception e) {
            e.printStackTrace();
            // Handle upload errors
            runOnUiThread(() -> Toast.makeText(MainActivity.this, "Error uploading to Dropbox: " + e.getMessage(), Toast.LENGTH_SHORT).show());
        }
    }



    private File createImageFile() {
        String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss", Locale.US).format(new Date());
        String imageFileName = "JPEG_" + timeStamp + "_";
        File storageDir = getExternalFilesDir(Environment.DIRECTORY_PICTURES);

        try {
            if (storageDir != null) {
                File tempFile = File.createTempFile(imageFileName, ".jpg", storageDir);
                // Log the file path for debugging
                System.out.println("File path: " + tempFile.getAbsolutePath());
                return tempFile;
            } else {
                runOnUiThread(() -> Toast.makeText(MainActivity.this, "Error creating storage directory", Toast.LENGTH_SHORT).show());
            }
        } catch (IOException e) {
            e.printStackTrace();
            runOnUiThread(() -> Toast.makeText(MainActivity.this, "Error creating photo file: " + e.getMessage(), Toast.LENGTH_SHORT).show());
        }

        return null;
    }



    private boolean allPermissionsGranted() {
        for (String permission : REQUIRED_CAMERA_PERMISSIONS) {
            if (ContextCompat.checkSelfPermission(this, permission) != PackageManager.PERMISSION_GRANTED) {
                return false;
            }
        }
        return true;
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);

        if (requestCode == CAMERA_PERMISSION_REQUEST) {
            if (allPermissionsGranted()) {
                startCamera();
                getLastLocation();
            } else {
                runOnUiThread(() -> Toast.makeText(this, "Camera permissions not granted.", Toast.LENGTH_SHORT).show());
                finish();
            }
        }
    }
}

one more thing i got error upload to Dropbox:null and i didn't find the solution yet so i considered that if i make the refresh token doesn't expire it could fix my problem