cannot be used in fragment

[Vishal-Likhitkar]

package com.appy.countrydetail;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;

import androidx.appcompat.app.AppCompatActivity;

import com.mukesh.countrypicker.Country;
import com.mukesh.countrypicker.CountryPicker;
import com.mukesh.countrypicker.OnCountryPickerListener;

public class MainActivity extends AppCompatActivity implements OnCountryPickerListener {

private TextView countryname,countryiso,countrydialcode,countrycurrency;
private ImageView countryflag;
private Button pickcountrybtn;
private CountryPicker countryPicker;
private Activity mActivity;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    intialize();
    setListener();
}
private void setListener() {
    pickcountrybtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            countryPicker.showDialog(getFragmentManager());
        }
    });
}
private  void intialize() {
    countryname = findViewById(R.id.selectedcountryname);
    countryiso = findViewById(R.id.Selectedcountryisocode);
    countrydialcode = findViewById(R.id.Selectedcountrydialcode);
    pickcountrybtn = findViewById(R.id.countrypickerbutton);
    countryflag = findViewById(R.id.country_flag);
    countrycurrency = findViewById(R.id.Selectedcountrycurrency);
    countryPicker = new CountryPicker.Builder().with(this)
            .listener(this)
            .build();
}
@Override
public void onSelectCountry(Country country){
    countryflag.setImageResource(country.getFlag());
    countrydialcode.setText(country.getDialCode());
    countryiso.setText(country.getCode());
    countryname.setText(country.getName());
    countrycurrency.setText(country.getCurrency());
}

}

I am getting error here
countryPicker.showDialog(getFragmentManager());

And the error is
countryPicker.showDialog(getFragmentManager());
^
class file for android.support.v4.app.FragmentManager not found

when I add this libraray is still showing error