Use the code below for different android versions
if (Build.VERSION.SDK_INT > Build.VERSION_CODES.O) {
ActivityCompat.requestPermissions(mActivity, new String[{android.permission.READ_PHONE_NUMBERS}, RC_PN);}
else {
TelephonyManager tMgr =(TelephonyManager)mAppContext.getSystemService(Context.TELEPHONY_SERVICE);
String mPhoneNumber = tMgr.getLine1Number();}
AndroidManifest.xml
<uses-permission android:name="android.permission.READ_PHONE_STATE"/>
<uses-permission android:name="android.permission.READ_PHONE_NUMBERS" />
<uses-permission android:name="android.permission.READ_SMS" />
More
Requires
Manifest.permission.READ_PHONE_STATE
or
Manifest.permission.READ_SMS
or
Manifest.permission.READ_PHONE_NUMBERS
Reference