activity_main.xml

<?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"
    tools:context=".MainActivity">

    <androidx.appcompat.widget.LinearLayoutCompat
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">
        <androidx.appcompat.widget.LinearLayoutCompat
            android:id="@+id/linearLayoutCompat1"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1"
            android:orientation="horizontal">
            <com.jjoe64.graphview.GraphView
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:id="@+id/graph1"/>
        </androidx.appcompat.widget.LinearLayoutCompat>
        <androidx.appcompat.widget.LinearLayoutCompat
            android:id="@+id/linearLayoutCompat2"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1"
            android:orientation="horizontal">
            <com.jjoe64.graphview.GraphView
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:id="@+id/graph2"/>
        </androidx.appcompat.widget.LinearLayoutCompat>
        <androidx.appcompat.widget.LinearLayoutCompat
            android:id="@+id/linearLayoutCompat3"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1"
            android:orientation="horizontal">
            <com.jjoe64.graphview.GraphView
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:id="@+id/graph3"/>
        </androidx.appcompat.widget.LinearLayoutCompat>
    </androidx.appcompat.widget.LinearLayoutCompat>

</androidx.constraintlayout.widget.ConstraintLayout>