Permissions

First, to request for permissions, we should give each of the requests a request code to signify which request we are processing. Add the following to the instance variables of SupFragment.java.

private static final int READ_CONTACTS = 1;
private static final int SEND_SMS = 2;

Next, we need to make a method to prompt the user for permission when we request access to each of these action. Create a new method getPermissionFromUser() in SupFragment.java.

/**
 * Prompts user for permission to perform a particular task.
 */
 
public void getPermissionFromUser(int request) {
    String permission = null;
    if (request == READ_CONTACTS) {
        permission = Manifest.permission.READ_CONTACTS;
    } else if (request == SEND_SMS) {
        permission = Manifest.permission.SEND_SMS;
    }
    if (permission != null &&
            ContextCompat.checkSelfPermission(getActivity().getApplicationContext(), permission)
                    != PackageManager.PERMISSION_GRANTED) {
        requestPermissions(new String[]{permission}, request);
    }
}

And then next add function calls to the top of the onClickListeners for mSelectFriend and mSendButton.

mSelectFriend.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        getPermissionFromUser(READ_CONTACTS);
        startActivityForResult(pickContact, REQUEST_CONTACT);
    }
});

mSendButton.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        getPermissionFromUser(SEND_SMS);
        if (mFriend.getPhoneNumber() != null) {
            sendSup();
        } else {
            sendCustomizedSupWithoutPhoneNumber();
        }
    }
});

Finally, we want to override the onRequestPermissionsResult() method in order to display a custom message to let the user know whether or not permission has been granted. We will do this via a toast. Add this override to SupFragment.java.

@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
    if (requestCode == READ_CONTACTS || requestCode == SEND_SMS) {
        String permission = null;
        if (requestCode == READ_CONTACTS) {
            permission = getString(R.string.read_contacts);
        } else if (requestCode == SEND_SMS) {
            permission = getString(R.string.send_sms);
        }
        if (permission != null) {
            String result = null;
            if (grantResults.length == 1 &&
                    grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                result = " permission granted";
            } else {
                result = " permission denied";
            }
            Toast.makeText(getActivity().getApplicationContext(),
                    permission + result, Toast.LENGTH_SHORT).show();
        }
    } else {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    }
}

And that should be all there is to it! Re-compile your app and then attempt selecting a contact and sending an SMS again. It should prompt you for permission and you can either grant or deny permission to do either action.