Proses Upload Image Android Studio

public class MainActivity extends AppCompatActivity {

    Button btnUpload, btnChoose;
    ImageView gambarUpload;
    final int CODE_GALLERY_REQUEST = 999;
    String url = "http://ipkalian atau domain hosting/upload_image/proses_upload.php";
    Bitmap bitmap;

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

        btnUpload = (Button) findViewById(R.id.btn_upload);
        btnChoose = (Button) findViewById(R.id.pilih_foto);
        gambarUpload = (ImageView) findViewById(R.id.imageupload);

        btnChoose.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.READ_EXTERNAL_STORAGE}, CODE_GALLERY_REQUEST);
            }
        });

        btnUpload.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                uploadImage();
            }
        });
    }

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

        if (requestCode == CODE_GALLERY_REQUEST){
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED){
                Intent intent = new Intent(Intent.ACTION_PICK);
                intent.setType("image/*");
                startActivityForResult(Intent.createChooser(intent, "Select Image"), CODE_GALLERY_REQUEST);
            }else{
                Toast.makeText(getApplicationContext(), "You don't have permission to access gallery!", Toast.LENGTH_LONG).show();
            }
            return;
        }
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (requestCode == CODE_GALLERY_REQUEST && resultCode == RESULT_OK && data != null){
            Uri path = data.getData();
                try {
                    InputStream inputStream = getContentResolver().openInputStream(path);
                    bitmap = BitmapFactory.decodeStream(inputStream);
                    gambarUpload.setImageBitmap(bitmap);
                    gambarUpload.setVisibility(View.VISIBLE);
                    btnUpload.setVisibility(View.VISIBLE);
                } catch (IOException e) {
                    e.printStackTrace();
            }
                Toast.makeText(MainActivity.this, "o", Toast.LENGTH_SHORT).show();
        }
        super.onActivityResult(requestCode, resultCode, data);
    }

    private void uploadImage(){
        StringRequest stringRequest = new StringRequest(Request.Method.POST, url, new Response.Listener<String>() {
            @Override
            public void onResponse(String response) {
                try {
                    JSONObject jsonObject = new JSONObject(response);
                    String Response = jsonObject.getString("response");
                    Toast.makeText(getApplicationContext(), Response, Toast.LENGTH_LONG).show();
                } catch (JSONException e) {
                    e.printStackTrace();
                }
            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                Toast.makeText(getApplicationContext(), "error: " + error.toString(), Toast.LENGTH_LONG).show();
            }
        })
        {
            @Override
            protected Map<String, String> getParams() throws AuthFailureError {
                Map<String, String> params = new HashMap<String, String>();
                String gambar = imagetoString(bitmap);
                params.put("foto", gambar);
                return params;
            }
        };
        RequestQueue requestQueue = Volley.newRequestQueue(MainActivity.this);
        requestQueue.add(stringRequest);
    }

    private String imagetoString(Bitmap bitmap)
    {
        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
        bitmap.compress(Bitmap.CompressFormat.JPEG, 100, byteArrayOutputStream);
        byte[] imageType = byteArrayOutputStream.toByteArray();
        return Base64.encodeToString(imageType, Base64.DEFAULT);
    }
}