filtering gridview with searchview

Question

This is my project. I want to add searching option with filtering but can't. Please help me. I am a slow new learner. I tried but couldn't find out the solution. How can i active my searching option. Sorry for my bad english.

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@drawable/building"
    tools:context=".MainActivity">

    <androidx.appcompat.widget.SearchView
        android:id="@+id/searchViewId"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_margin="8dp"
        android:background="@drawable/search_view_bg"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        android:elevation="@dimen/cardview_default_elevation"
        app:queryHint="search here..."/>

    <GridView
        android:id="@+id/gridView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:listSelector="#62caaf"
        android:layout_marginTop="70dp"
        android:layout_marginLeft="10dp"
        android:layout_marginRight="10dp"
        android:layout_marginBottom="10dp"
        android:numColumns="3"
        android:horizontalSpacing="10dp"
        android:verticalSpacing="10dp">

    </GridView>


</androidx.constraintlayout.widget.ConstraintLayout>

MainActivity

package com.example.newvisacheckallcountry;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.widget.GridView;
import android.widget.SearchView;

public class MainActivity extends AppCompatActivity {

    int[] flags = {R.drawable.australia,R.drawable.austria,R.drawable.argentina,
    R.drawable.armenia,R.drawable.belgium,R.drawable.brazil,R.drawable.bangladesh,
    R.drawable.belarus,R.drawable.brunei,R.drawable.canada,R.drawable.cameroon,R.drawable.china};

    String[] countryNames;

    private GridView gridView;

    private SearchView searchView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        searchView = findViewById(R.id.searchViewId);

        countryNames = getResources().getStringArray(R.array.country_names);

        gridView = findViewById(R.id.gridView);

        CustomAdapter adapter = new CustomAdapter(this, countryNames,flags);
        gridView.setAdapter(adapter );

    }
}

CustomAdapter

package com.example.newvisacheckallcountry;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;

public class CustomAdapter extends BaseAdapter {

    Context context;
    int[]  flags;
    String[] countryNames;

    private LayoutInflater inflater;

    CustomAdapter(Context context,String[] countryNames,int[] flags){
        this.context = context;
        this.countryNames = countryNames;
        this.flags = flags;
    }

    @Override
    public int getCount() {
        return countryNames.length;
    }

    @Override
    public Object getItem(int position) {
        return null;
    }

    @Override
    public long getItemId(int position) {
        return 0;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        if (convertView == null){
            inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = inflater.inflate(R.layout.sample_view,parent,false);
        }

        ImageView imageView = convertView.findViewById(R.id.imagViewId);
        TextView textView = convertView.findViewById(R.id.textViewId);

        imageView.setImageResource(flags[position]);
        textView.setText(countryNames[position]);

        return convertView;
    }
}

sample_view.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.cardview.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    app:cardCornerRadius="10dp"
    android:elevation="@dimen/cardview_compat_inset_shadow"
    app:layout_constraintCircleRadius="20dp">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        android:background="@color/white"
        android:padding="5dp">

        <ImageView
            android:id="@+id/imagViewId"
            android:layout_width="50dp"
            android:layout_height="50dp"
            android:layout_gravity="center_horizontal"
            android:scaleType="fitCenter"
            android:src="@drawable/australia"/>
        <TextView
            android:id="@+id/textViewId"
            android:textAppearance="?android:attr/textAppearanceMedium"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Australia"
            android:layout_gravity="center_horizontal"/>

    </LinearLayout>
</androidx.cardview.widget.CardView>

strings.xml

<resources>
    <string name="app_name">NewVisaCheckAllCountry</string>

    <string-array name="country_names">
        <item>Australia</item>
        <item>Austria</item>
        <item>Argentina</item>
        <item>Armenia</item>
        <item>Belgium</item>
        <item>Brazil</item>
        <item>Bangladesh</item>
        <item>Belarus</item>
        <item>Brunei</item>
        <item>Canada</item>
        <item>Cameroon</item>
        <item>China</item>
    </string-array>
</resources>

here is my project. thank you.