java - Refresh viewpager recyclerview data

Question

I made a nested action bar tabs with viewpager like this. However, the data does not appear in the Recycler view when I click the menu at first, and then the data is loaded and displayed in the Recycler view after clicking all the menus in order. I want to show the data as soon as I enter the page. What should I do?

when I first enter the page, data won't show up.

after clicking all menus then the list shows up.

Here is my code. I have many menus in tab layout so, I will attach only a part.

merge.java activity code(first tab layout)

package com.eos.youareheroine;

import android.content.Intent;
import android.content.SharedPreferences;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.util.Log;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.ImageButton;
import android.widget.ImageView;
import android.widget.TextView;

import androidx.core.view.GravityCompat;
import androidx.drawerlayout.widget.DrawerLayout;
import androidx.fragment.app.FragmentActivity;
import androidx.viewpager.widget.ViewPager;

import com.eos.youareheroine.MyPage.MyPageActivity;
import com.google.android.material.navigation.NavigationView;
import com.google.android.material.tabs.TabLayout;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
import com.kakao.sdk.user.UserApiClient;

import kotlin.Unit;
import kotlin.jvm.functions.Function1;


public class merge extends FragmentActivity {

    private Button main;
    private ImageButton search;
    TabLayout tabs;
    MergePageAdapter adapter;


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


        tabs = findViewById(R.id.merge_tab);
        ViewPager viewPager = findViewById(R.id.merge_view_pager);
        adapter = new MergePageAdapter(getSupportFragmentManager());
        viewPager.setAdapter(adapter);
        tabs.setupWithViewPager(viewPager);

        main = findViewById(R.id.merge_btn_title);
        search = findViewById(R.id.merge_ibtn_search);
        Drawable drawable = getDrawable(R.drawable.iv_search_black);
        search.setImageDrawable(drawable);

        main.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(merge.this, MainActivity.class);
                intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                startActivity(intent);
            }
        });

        search.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(merge.this, SearchPageActivity.class);
                startActivity(intent);
            }
        });


    }

    @Override
    protected void onResume() {
        super.onResume();
        adapter.notifyDataSetChanged();

         
    public void refresh() {
        adapter.notifyDataSetChanged();

    }

  
}

merge.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.drawerlayout.widget.DrawerLayout 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:id="@+id/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

<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"
    tools:context=".merge">

    <androidx.appcompat.widget.Toolbar
        android:id="@+id/main_toolbar"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:background="#EDD0FF"
        android:gravity="center"
        android:minHeight="?attr/actionBarSize"
        android:theme="?attr/actionBarTheme"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:titleMargin="4dp"
        app:titleTextColor="#000000" />

    <Button
        android:id="@+id/merge_btn_title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="#00D6D5F4"
        android:fontFamily="@font/kalam"
        android:gravity="center"
        android:textAllCaps="false"
        android:stateListAnimator="@null"
        android:text="Story for me"
        android:textColor="#000000"
        android:textSize="26dp"
        app:layout_constraintBottom_toBottomOf="@+id/main_toolbar"
        app:layout_constraintEnd_toEndOf="@+id/main_toolbar"
        app:layout_constraintStart_toStartOf="@+id/main_toolbar"
        app:layout_constraintTop_toTopOf="parent" />

    <ImageButton
        android:id="@+id/merge_ibtn_search"
        android:layout_width="40dp"
        android:layout_height="40dp"
        android:layout_marginEnd="10dp"
        android:background="#00FFFFFF"
        android:scaleType="fitXY"
        app:layout_constraintBottom_toBottomOf="@+id/main_toolbar"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:srcCompat="@drawable/iv_search_black" />

    <ImageButton
        android:id="@+id/ibtn_navi"
        android:layout_width="35dp"
        android:layout_height="40dp"
        android:layout_marginStart="10dp"
        android:background="#00FFFFFF"
        android:clickable="false"
        android:scaleType="fitXY"
        android:tint="#B888FF"
        app:layout_constraintBottom_toBottomOf="@+id/main_toolbar"
        app:layout_constraintStart_toStartOf="@+id/main_toolbar"
        app:layout_constraintTop_toTopOf="parent"
        app:srcCompat="@drawable/ic_list" />

    <com.google.android.material.tabs.TabLayout
        android:id="@+id/merge_tab"
        android:layout_width="match_parent"
        android:layout_height="45dp"
        android:background="#EDD0FF"
        android:elevation="1dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/main_toolbar"
        app:tabGravity="fill"
        app:tabIndicatorColor="#9C46E6"
        app:tabMode="fixed"
        app:tabSelectedTextColor="#9C46E6"
        app:tabTextColor="#000000">

        <com.google.android.material.tabs.TabItem
            android:id="@+id/tab_latest"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="??" />

        <com.google.android.material.tabs.TabItem
            android:id="@+id/tab_finish"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="??" />

        <com.google.android.material.tabs.TabItem
            android:id="@+id/tab_rank"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="??" />

    </com.google.android.material.tabs.TabLayout>

    <androidx.viewpager.widget.ViewPager
        android:id="@+id/merge_view_pager"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/merge_tab" />



</androidx.constraintlayout.widget.ConstraintLayout>

    <com.google.android.material.navigation.NavigationView
        android:id="@+id/nav_view"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:fitsSystemWindows="true"
        app:headerLayout="@layout/navi_my_page"
        app:menu="@menu/navi_menu" />


</androidx.drawerlayout.widget.DrawerLayout>

first tab page adapter(FragRankAdapter.java)

package com.eos.youareheroine;

import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.fragment.app.FragmentPagerAdapter;
import androidx.fragment.app.FragmentStatePagerAdapter;

import java.util.ArrayList;

public class FragRankPageAdapter extends FragmentStatePagerAdapter {

    private ArrayList<Fragment> mData;
    private ArrayList<String> name;
    public FragRankPageAdapter(@NonNull FragmentManager fm){
        super(fm);
        mData = new ArrayList<>();
        mData.add(new frag_rank_week());
        mData.add(new frag_rank_month());
        mData.add(new frag_rank_hof());


        name = new ArrayList<>();
        name.add("?? ??");
        name.add("?? ??");
        name.add("??? ??");

    }

    public CharSequence getPageTitle(int position){
        return name.get(position);
    }

    @NonNull
    @Override
    public Fragment getItem(int position) {
        return mData.get(position);
    }

    @Override
    public int getCount() {
        return mData.size();
    }

    @Override
    public int getItemPosition(@NonNull Object object) {
        return POSITION_NONE;
    }


}

second tab layout xml(fragment_rank.xml) (inside in first tab layout)

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout 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"
    tools:context=".rank">

    <!-- TODO: Update blank fragment layout -->

    <com.google.android.material.tabs.TabLayout
        android:id="@+id/frag_rank_tab"
        android:layout_width="match_pa

Answer 1

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