handlePermissionResult.java

@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
  if (requestCode == WRITE_EXTERNAL_STORAGE_REQUEST_CODE){
    if (grantResults[0] == PackageManager.PERMISSION_GRANTED)
      captureImage();
    else{
          if (shouldShowRequestPermissionRationale(Manifest.permission.WRITE_EXTERNAL_STORAGE))
            showRationaleDialog();
          else
            Toast.makeText(MainActivity.this, "You need to allow permission to Write to External Storage", Toast.LENGTH_LONG).show();
        }
  }
  super.onRequestPermissionsResult(requestCode, permissions, grantResults);
}

private void showRationaleDialog(){
  new AlertDialog.Builder(MainActivity.this)
    .setMessage("Application needs access to READ/WRITE LocalStorage to store images.")
    .setPositiveButton("OK", new DialogInterface.OnClickListener() {
      @Override
      public void onClick(DialogInterface dialog, int which) {
        requestPermissionWriteToLocalStorage();
      }
    })
    .setNegativeButton("Cancel", null)
    .create()
    .show();
}