buttonResend = findViewById(R.id.buttonResend);

    final String phonenumber = getIntent().getStringExtra("phonenumber");
    sendVerificationCode(phonenumber);

findViewById(R.id.buttonResend).setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            String code = editTextCode.getText().toString().trim();
            resendVerificationCode(phonenumber, token);
        }
    });

}

private void sendVerificationCode(String number) {
    progressBar.setVisibility(View.VISIBLE);
    PhoneAuthProvider.getInstance().verifyPhoneNumber(
            number,                         // Phone number to verify
            60,                          // Timeout duration
            TimeUnit.SECONDS,               // Unit of timeout
            TaskExecutors.MAIN_THREAD,      // Activity (for callback binding)
            mCallbacks);
}

private void resendVerificationCode(String number, PhoneAuthProvider.ForceResendingToken token) {
    PhoneAuthProvider.getInstance().verifyPhoneNumber(
            number,             // Phone number to verify
            60,              // Timeout duration
            TimeUnit.SECONDS,   // Unit of timeout
            this,        // Activity (for callback binding)
            mCallbacks,         // OnVerificationStateChangedCallbacks
            token);             // ForceResendingToken from callbacks
}