Task 1

package com.example.zer.task2_1;

import android.os.Handler;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

    static int i = 1;
    static int previ = 0;

    Handler handler = new Handler();
    Runnable r;

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

        r = new Runnable() {
            @Override
            public void run() {

                if (i > previ && i < 4) {
                    previ = i;
                    i++;
                } else if (i > 1) {
                    previ = i;
                    i--;
                } else {
                    previ = i;
                    i++;
                }

                tts(i);
                handler.postDelayed(r, 1000);
            }
        };
        FragmentManager fm = getSupportFragmentManager();
        FragmentTransaction ft = fm.beginTransaction();
        Fragment1 fragment = Fragment1.newInstance();
        ft.add(R.id.container, fragment, Fragment1.class.getSimpleName());
        ft.commit();
        handler.postDelayed(r, 1000);
    }

    private void tts(int j) {
        FragmentManager fm1 = getSupportFragmentManager();
        FragmentTransaction ft1 = fm1.beginTransaction();

        switch (j) {
            case 1:
                Fragment1 fragment1 = Fragment1.newInstance();
                ft1.replace(R.id.container, fragment1, Fragment1.class.getSimpleName());
                ft1.commit();
                break;
            case 2:
                Fragment2 fragment2 = Fragment2.newInstance();
                ft1.replace(R.id.container, fragment2, Fragment2.class.getSimpleName());
                ft1.commit();
                break;
            case 3:
                Fragment3 fragment3 = Fragment3.newInstance();
                ft1.replace(R.id.container, fragment3, Fragment3.class.getSimpleName());
                ft1.commit();
                break;
            case 4:
                Fragment4 fragment4 = Fragment4.newInstance();
                ft1.replace(R.id.container, fragment4, Fragment4.class.getSimpleName());
                ft1.commit();
                break;
        }
    }
}

package com.example.zer.task2_1;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class Fragment1 extends Fragment {

    public static Fragment1 newInstance() {
        Fragment1 fr = new Fragment1();
        return fr;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View root = inflater.inflate(R.layout.fragment_1, container, false);
        return root;
    }
}

package com.example.zer.task2_1;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class Fragment2 extends Fragment {

    public static Fragment2 newInstance() {
        Fragment2 fr = new Fragment2();
        return fr;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View root = inflater.inflate(R.layout.fragment_2, container, false);
        return root;
    }
}

package com.example.zer.task2_1;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class Fragment3 extends Fragment {

    public static Fragment3 newInstance() {
        Fragment3 fr = new Fragment3();
        return fr;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View root = inflater.inflate(R.layout.fragment_3, container, false);
        return root;
    }
}

package com.example.zer.task2_1;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class Fragment4 extends Fragment {

    public static Fragment4 newInstance() {
        Fragment4 fr = new Fragment4();
        return fr;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View root = inflater.inflate(R.layout.fragment_4, container, false);
        return root;
    }
}

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.zer.task2_1.MainActivity">

    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/container"
        android:layout_alignParentTop="true"
        android:layout_alignParentStart="true">

    </FrameLayout>
</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:text="fragment_1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerVertical="true"
        android:layout_centerHorizontal="true"
        android:textSize="48sp"/>
</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:text="fragment_2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerVertical="true"
        android:layout_centerHorizontal="true"
        android:textSize="48sp"/>
</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent" android:layout_height="match_parent">

    <TextView
        android:text="fragment_3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerVertical="true"
        android:layout_centerHorizontal="true"
        android:textSize="48sp"/>
</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent" android:layout_height="match_parent">

    <TextView
        android:text="fragment_4"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerVertical="true"
        android:layout_centerHorizontal="true"
        android:textSize="48sp"/>
</RelativeLayout>