activity_main.xml sqlite

<?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="@android:color/holo_blue_bright"
    tools:context="com.examhhhhhhhhple.seruuusdsdsudo.myapplication.MainActivity">

    <TextView
        android:id="@+id/textView"
        android:layout_width="350dp"
        android:layout_height="150dp"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:layout_marginBottom="17dp"
        android:gravity="center_horizontal"
        android:text=""
        android:textSize="20sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.955" />

    <EditText
        android:id="@+id/firstname_input"
        android:layout_width="350dp"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/textView"
        android:layout_alignParentTop="true"
        android:layout_alignStart="@+id/textView"
        android:layout_marginTop="12dp"
        android:ems="10"
        android:hint="Firstname"
        android:inputType="textPersonName"
        app:layout_constraintHorizontal_bias="0.171"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <EditText
        android:id="@+id/lastname_input"
        android:layout_width="350dp"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/firstname_input"
        android:layout_alignStart="@+id/firstname_input"
        android:layout_below="@+id/firstname_input"
        android:layout_marginTop="15dp"
        android:ems="10"
        android:hint=" Lstename"
        android:inputType="textPersonName"
        app:layout_constraintHorizontal_bias="0.176"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        tools:layout_editor_absoluteY="72dp" />

    <Button
        android:id="@+id/btn_add"
        android:layout_width="200dp"
        android:layout_height="40dp"
        android:layout_above="@+id/btn_del"
        android:layout_alignLeft="@+id/btn_del"
        android:layout_alignStart="@+id/btn_del"
        android:onClick="btn_click"
        android:text="Add Student"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        tools:layout_editor_absoluteY="127dp" />

    <Button
        android:id="@+id/btn_del"
        android:layout_width="200dp"
        android:layout_height="40dp"
        android:layout_above="@+id/btn_update"
        android:layout_alignLeft="@+id/btn_update"
        android:layout_alignStart="@+id/btn_update"
        android:onClick="btn_click"
        android:text="DELETE student"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        tools:layout_editor_absoluteY="179dp" />

    <Button
        android:id="@+id/btn_update"
        android:layout_width="200dp"
        android:layout_height="40dp"
        android:layout_above="@+id/btn_show"
        android:layout_alignLeft="@+id/btn_show"
        android:layout_alignStart="@+id/btn_show"
        android:layout_marginBottom="13dp"
        android:onClick="btn_click"
        android:text="UPDATE liste"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.498" />

    <Button
        android:id="@+id/btn_show"
        android:layout_width="200dp"
        android:layout_height="40dp"
        android:layout_above="@+id/textView"
        android:layout_centerHorizontal="true"
        android:layout_marginBottom="14dp"
        android:onClick="btn_click"
        android:text="LIste students"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        tools:layout_editor_absoluteY="287dp" />

</RelativeLayout>