I am trying to get my own number in android. I search on internet and I found that if your number is not available in Settings>About Phone>Status>My phone number it shows unknown then by using below code you cannot get phone number. I have also added permission
<uses-permission android:name="android.permission.READ_PHONE_STATE"/>
TelephonyManager tm = (TelephonyManager)this.getSystemService(Context.TELEPHONY_SERVICE);
String mPhoneNumber = tm.getLine1Number();
here is my phone screen shot
Now I don't know facebook app gets my phone number correctly.
Here my facebook sign up screen.
can someone please tell me how facebook is able to get phone number.