XO, ver 1.0 - 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">

    <ImageButton
        android:id="@+id/ibtn21"
        android:layout_width="0dp"
        android:layout_height="90dp"
        android:onClick="btnClicked"
        android:scaleType="fitXY"
        app:layout_constraintEnd_toStartOf="@+id/ibtn22"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toEndOf="@+id/ibtn20"
        app:layout_constraintTop_toTopOf="@+id/ibtn20"
        app:srcCompat="@android:drawable/btn_dialog" />

    <ImageButton
        android:id="@+id/ibtn20"
        android:layout_width="0dp"
        android:layout_height="90dp"
        android:onClick="btnClicked"
        android:scaleType="fitXY"
        app:layout_constraintEnd_toStartOf="@+id/ibtn21"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/ibtn10"
        app:srcCompat="@android:drawable/btn_dialog" />

    <ImageButton
        android:id="@+id/ibtn22"
        android:layout_width="0dp"
        android:layout_height="90dp"
        android:onClick="btnClicked"
        android:scaleType="fitXY"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toEndOf="@+id/ibtn21"
        app:layout_constraintTop_toTopOf="@+id/ibtn21"
        app:srcCompat="@android:drawable/btn_dialog" />

    <ImageButton
        android:id="@+id/ibtn11"
        android:layout_width="0dp"
        android:layout_height="90dp"
        android:onClick="btnClicked"
        android:scaleType="fitXY"
        app:layout_constraintEnd_toStartOf="@+id/ibtn12"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toEndOf="@+id/ibtn10"
        app:layout_constraintTop_toTopOf="@+id/ibtn10"
        app:srcCompat="@android:drawable/btn_dialog" />

    <ImageButton
        android:id="@+id/ibtn10"
        android:layout_width="0dp"
        android:layout_height="90dp"
        android:onClick="btnClicked"
        android:scaleType="fitXY"
        app:layout_constraintEnd_toStartOf="@+id/ibtn11"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/ibtn00"
        app:srcCompat="@android:drawable/btn_dialog" />

    <ImageButton
        android:id="@+id/ibtn12"
        android:layout_width="0dp"
        android:layout_height="90dp"
        android:onClick="btnClicked"
        android:scaleType="fitXY"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toEndOf="@+id/ibtn11"
        app:layout_constraintTop_toTopOf="@+id/ibtn11"
        app:srcCompat="@android:drawable/btn_dialog" />

    <ImageButton
        android:id="@+id/ibtn00"
        android:layout_width="0dp"
        android:layout_height="90dp"
        android:layout_marginTop="150dp"
        android:onClick="btnClicked"
        android:scaleType="fitXY"
        app:layout_constraintEnd_toStartOf="@+id/ibtn01"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:srcCompat="@android:drawable/btn_dialog" />

    <ImageButton
        android:id="@+id/ibtn01"
        android:layout_width="0dp"
        android:layout_height="90dp"
        android:onClick="btnClicked"
        android:scaleType="fitXY"
        app:layout_constraintEnd_toStartOf="@+id/ibtn02"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toEndOf="@+id/ibtn00"
        app:layout_constraintTop_toTopOf="@+id/ibtn00"
        app:srcCompat="@android:drawable/btn_dialog" />

    <ImageButton
        android:id="@+id/ibtn02"
        android:layout_width="0dp"
        android:layout_height="90dp"
        android:onClick="btnClicked"
        android:scaleType="fitXY"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toEndOf="@+id/ibtn01"
        app:layout_constraintTop_toTopOf="@+id/ibtn01"
        app:srcCompat="@android:drawable/btn_dialog" />
</androidx.constraintlayout.widget.ConstraintLayout>