public class MainActivity extends AppCompatActivity {

    private static final int REQUEST_CODE_SAVE_FILE_PERMISSION = 1;
    private static final String[] PERMISSIONS_SAVE_FILE = {
            Manifest.permission.WRITE_EXTERNAL_STORAGE
    };

    ...

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

        // Dispatch to our library.
        EffortlessPermissions.onRequestPermissionsResult(requestCode, permissions, grantResults,
                this);
    }

    // Call back to the same method so that we'll check and proceed.
    @AfterPermissionGranted(REQUEST_CODE_SAVE_FILE_PERMISSION)
    private void saveFile() {
        if (EffortlessPermissions.hasPermissions(this, PERMISSIONS_SAVE_FILE)) {
            // We've got the permission.
            saveFileWithPermission();
        } else {
            // Request the permissions.
            EffortlessPermissions.requestPermissions(this,
                    R.string.save_file_permission_request_message,
                    REQUEST_CODE_SAVE_FILE_PERMISSION, PERMISSIONS_SAVE_FILE);
        }
    }

    @AfterPermissionDenied(REQUEST_CODE_SAVE_FILE_PERMISSION)
    private void onSaveFilePermissionDenied() {
        if (EffortlessPermissions.somePermissionPermanentlyDenied(this, PERMISSIONS_SAVE_FILE)) {
            // Some permission is permanently denied so we cannot request them normally.
            OpenAppDetailsDialogFragment.show(
                    R.string.save_file_permission_permanently_denied_message,
                    R.string.open_settings, this);
        } else {
            // User denied at least some of the required permissions, report the error.
            Toast.makeText(this, R.string.save_file_permission_denied, Toast.LENGTH_SHORT).show();
        }
    }

    private void saveFileWithPermission() {
        // It's show time!
        Toast.makeText(this, R.string.save_file_show_time, Toast.LENGTH_SHORT).show();
    }
}