xml files

layout_activity_main.xml

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

layout_fragment_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    tools:context=".MainActivity$PlaceholderFragment">

    <TextView
        android:text="@string/exav"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/exav"
        android:textColor="#ff174abc"
        android:textSize="40dp" />

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/imageView"
        android:src="@mipmap/image"
        android:layout_below="@+id/exav"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="74dp" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hi! I am Exaviser! and I will help you revise your exams."
        android:id="@+id/textView"
        android:layout_below="@+id/imageView"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_marginTop="40dp" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Start"
        android:id="@+id/button"
        android:layout_below="@+id/textView"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="55dp" />

</RelativeLayout>

layout_tab_fragment_1.xml

<?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">

    <!-- Do the same for tab_fragment_2 and tab_fragment_3 -->

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text=""
        android:textSize="16sp"/>


<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Create Database"
    android:id="@+id/createDBButton"
    android:layout_alignParentTop="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:onClick="createDatabase"/>

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Add Contact"
    android:id="@+id/addContactButton"
    android:layout_alignParentTop="true"
    android:layout_toRightOf="@+id/createDBButton"
    android:layout_toEndOf="@+id/createDBButton"
    android:layout_marginLeft="10dp"
    android:onClick="addContact"
    android:clickable="false" />

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Delete Contact"
    android:id="@+id/deleteContactButton"
    android:layout_below="@+id/createDBButton"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:onClick="deleteContact"
    android:clickable="false"/>

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Get Contacts"
    android:id="@+id/getContactsButton"
    android:layout_below="@+id/createDBButton"
    android:layout_toRightOf="@+id/deleteContactButton"
    android:layout_toEndOf="@+id/deleteContactButton"
    android:layout_marginLeft="10dp"
    android:onClick="getContacts"
    android:clickable="false"/>

<EditText
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/nameEditText"
    android:layout_below="@+id/deleteContactButton"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:hint="Name"
    android:layout_marginTop="5dp"/>

<EditText
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/emailEditText"
    android:layout_below="@+id/nameEditText"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:hint="Email"
    android:layout_marginTop="5dp"
    android:inputType="textEmailAddress"/>

<EditText
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:inputType="number"
    android:ems="10"
    android:id="@+id/idEditText"
    android:layout_below="@+id/emailEditText"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:hint="ID to Delete"
    android:layout_marginTop="5dp"/>

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Delete Database"
    android:id="@+id/deleteDBButton"
    android:onClick="deleteDatabase"
    android:layout_below="@+id/idEditText"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:clickable="false" />

<EditText
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:inputType="textMultiLine"
    android:ems="10"
    android:id="@+id/contactListEditText"
    android:lines="8"
    android:layout_alignParentBottom="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true" />

</RelativeLayout>

layout_tab_fragment_2.xml

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

    <!-- Do the same for tab_fragment_2 and tab_fragment_3 -->

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Tab Fragment 2"
        android:textSize="16sp"/>

</LinearLayout>

layout_tab_fragment_3.xml

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

    <!-- Do the same for tab_fragment_2 and tab_fragment_3 -->

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Tab Fragment 3"
        android:textSize="16sp"/>

</LinearLayout>