Send text to Viber and Facebook Messenger with Flutter

How can I send a text directly to a specific phone number on Viber? or to a specific person on Facebook messenger?

with whatsapp I'm using url_launcher with whatsapp with below code, and it is working fine.

var whatsapp_url = "whatsapp://send?phone=" + whatsapp_number + "&text=hellooo";
try {
await launchUrl(Uri.parse(whatsapp_url));
} catch (e) {
print('could not launch whatsapp');
}

I tried using the same package with Viber using ("viber://chat?number=") and Facebook messenger using ('m.me/username') but both are just opening a web site and not opening the mobile App and not finding the phone number or the messenger chat.

I need to do a similar thing by clicking an IconButton to open a specific chat on Viber and another IconButton to open a specific Facebook messenger chat.

I found a solution in case someone needed - I used the same url_launcher library.

• Viber:

  var viber_link = "viber://chat/?number=$Country_Code$Mobile_Number&draft=$Message_to_be_sen” 
  ;
  

  Viber doesn’t need ‘+’ sign when writing the country code

• Facebook Messenger:

  var facebook_messenger_link = 'https://m.me/$FaceBook_Name?text=$Message_to_be_sent;
  

  Facebook Name can be found by clicking on the profile picture on Facebook and checking the URL, it comes after ‘https://www.facebook.com/{FB_Name}’

• Telegram:

  var telegram_link = 'https://t.me/+$Country_Code$Mobile_Number&draft=$Message_to_be_sen';
  

  Telegram needs the ‘+’ sign when writing the country code

Then used this code for launching it:

final Uri app_link_uri = Uri.parse(app_link);
  try {
    await launchUrl(
      app_link_uri,
      mode: LaunchMode.externalApplication,
    );
  } catch (error) {
    print(‘error’ catching: $error);
  }