captureImage.java

private final int WRITE_EXTERNAL_STORAGE_REQUEST_CODE = 123

private void takePhoto() {
  //Make sure we have permission to write to external storage
  int hasWriteExternalStoragePermission = checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE);
  if (hasWriteExternalStoragePermission == PackageManager.PERMISSION_GRANTED)
    captureImage()
  else
    requestPermissionWriteToLocalStorage();
}

private void captureImage(){
  //Code to capture image from camera
}

private void requestPermissionWriteToLocalStorage(){
  requestPermissions(new String[] {Manifest.permission.WRITE_EXTERNAL_STORAGE}, WRITE_EXTERNAL_STORAGE_REQUEST_CODE);
}