WHAT IS WALKTHROUGH SCREEN OR ONBOADING SCREEN? 

XML LAYOUT DESIGN 

• First Download XD design and Export the design as drawables
• After exporting, import drawables to your android studio project as drawables.
• Download Gotham and Monsterrat fonts.
• Create Android Resource directory and paste downloaded font in that directory name font
• create new android layout activity name slider_layout.
• Copy and paste this xml code in the newly created slider_layout

<?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">

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginTop="90dp"
        android:layout_marginEnd="8dp"
        android:src="@drawable/s_distance_img"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginTop="32dp"
        android:layout_marginEnd="8dp"
        android:fontFamily="@font/gotham_medium"
        android:text="HEADING"
        android:textStyle="bold"
        android:textColor="#372B7B"
        android:textSize="20sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/imageView" />

    <TextView
        android:id="@+id/description"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="8dp"
        android:fontFamily="@font/montserrat"
        android:padding="10dp"
        android:text="Avoid close contact with people who are sick. When you are sick, keep your distance from others to protect them from getting sick too."
        android:gravity="center"
        android:textColor="#3A2F81"
        android:textSize="16sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView" />

</androidx.constraintlayout.widget.ConstraintLayout>

•  In the activity_main paste this xml code

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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/app_bg"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <androidx.viewpager.widget.ViewPager
        android:id="@+id/viewpager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

    </androidx.viewpager.widget.ViewPager>


    <TextView
        android:id="@+id/back"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentStart="true"
        android:layout_alignParentBottom="true"
        android:layout_marginStart="20dp"
        android:layout_marginBottom="20dp"
        android:fontFamily="@font/gotham_medium"
        android:text="@string/back"
        android:textColor="#3A2F81"
        android:textSize="16sp"
        android:textStyle="bold" />


    <TextView
        android:id="@+id/next"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentEnd="true"
        android:layout_alignParentBottom="true"
        android:layout_marginEnd="20dp"
        android:layout_marginBottom="20dp"
        android:fontFamily="@font/gotham_medium"
        android:text="@string/next"
        android:textColor="#3A2F81"
        android:textSize="16sp"
        android:textStyle="bold" />

</RelativeLayout>

•  Create a new Java Class named SliderAdapter
• Paste this java code in the newly created java class

package com.ayowainc.ob;

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

import androidx.annotation.NonNull;
import androidx.constraintlayout.widget.ConstraintLayout;
import androidx.viewpager.widget.PagerAdapter;

public class SliderAdapter extends PagerAdapter {

    private Context context;

    SliderAdapter(Context context) {
        this.context = context;
    }

    //Arrays
    private int[]slider_images = {
            R.drawable.s_distance_img,
            R.drawable.wash_hands_img,
            R.drawable.stay_home_img,
            R.drawable.cover_mouth_img,
            R.drawable.disinfect_img,
            R.drawable.elif_logo
    };

    private String[]headings = {
            "AVOID CLOSE CONTACT", "CLEAN YOUR HANDS","STAY HOME","COVER MOUTH","CLEAN AND DISINFECT","INFO FROM ELIF"
    };

    private String[]descriptions = {
            "Avoid close contact with people who are sick.  When you are sick, keep your distance from others to protect them form getting sick too.",
            "COVID-19 is often spread when a person touches something that is contaminated with the Virus. Washing your hands often will help protect you from this Virus.",
            "If possible, stay home from work, school, and errands when you are sick.  You will help prevent others from catching the virus.",
            "Cover your mouth and nose with a tissue when coughing or sneezing.  It may prevent those around you from getting sick.",
            "Always try your best possible way to disinfect and clean your household,offices,churches,schools, stadiums,etc",
            "Hey! Viewers COVID-19 is real, let's come together and fight this noveal virus from our society. Please Stay Home, Stay Safe and Subscribe"
    };

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

    @Override
    public boolean isViewFromObject(@NonNull View view, @NonNull Object object) {
        return view == (ConstraintLayout) object;
    }

    @NonNull
    @Override
    public Object instantiateItem(@NonNull ViewGroup container, int position) {
        LayoutInflater layoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        View view = layoutInflater.inflate(R.layout.activity_slide_layout, container, false);

        ImageView sliderImages = (ImageView) view.findViewById(R.id.imageView);
        TextView sliderHeading = (TextView)view.findViewById(R.id.textView);
        TextView sliderDesc = (TextView) view.findViewById(R.id.description);

        sliderImages.setImageResource(slider_images[position]);
        sliderHeading.setText(headings[position]);
        sliderDesc.setText(descriptions[position]);

        container.addView(view);
        return view;

    }

    @Override
    public void destroyItem(@NonNull ViewGroup container, int position, @NonNull Object object) {
        container.removeView((ConstraintLayout)object);
    }
}

•  In the MainActivity.java paste this line of code

package com.ayowainc.ob;

import android.os.Bundle;
import android.view.View;
import android.view.WindowManager;
import android.widget.TextView;

import androidx.appcompat.app.AppCompatActivity;
import androidx.viewpager.widget.ViewPager;

public class MainActivity extends AppCompatActivity {
    private ViewPager slideViewPager;
    private TextView Next, Back;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        slideViewPager = (ViewPager) findViewById(R.id.viewpager);
        Next = findViewById(R.id.next);
        Back = findViewById(R.id.back);
        Back.setVisibility(View.INVISIBLE);

        SliderAdapter sliderAdapter = new SliderAdapter(this);
        slideViewPager.setAdapter(sliderAdapter);

        Next.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View view) {
                slideViewPager.setCurrentItem(slideViewPager.getCurrentItem() + 1, true);
            }
        });


        Back.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View view) {
                slideViewPager.setCurrentItem(slideViewPager.getCurrentItem() - 1, true);
            }
        });

        slideViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            private int i;
            private float v;
            private int i1;

            @Override
            public void onPageScrolled(int i, float v, int i1) {

                this.i = i;
                this.v = v;
                this.i1 = i1;
            }

            @Override
            public void onPageSelected(int position) {
                if (position == 0) {
                    Back.setVisibility(View.INVISIBLE);
                } else {
                    Back.setVisibility(View.VISIBLE);
                }
                if (position < slideViewPager.getAdapter().getCount() - 1) {
                    Next.setVisibility(View.VISIBLE);
                } else {
                    Next.setVisibility(View.INVISIBLE);
                }
            }

            @Override
            public void onPageScrollStateChanged(int i) {

                this.i = i;
            }
        });
    }


}