Android XML Layout with imagebuttons in a row

Im trying to create a row of image buttons, so lets say 3 rows and 3 columns.

I keep trying to make the images all the same size but the design just messes up.

Trying to get something like this:

Image Image Image

Image Image Image

Image Image Image

Can someone help me get these in line?

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://ift.tt/nIICcg"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:weightSum="1">

    <ImageButton
        android:layout_width="100dp"
        android:layout_height="172dp"
        android:id="@+id/imageButton"
        android:src="@drawable/sample_0"
        android:layout_gravity="center_horizontal" />

    <ImageButton
        android:layout_width="129dp"
        android:layout_height="180dp"
        android:id="@+id/imageButton2"
        android:src="@drawable/sample_1" />

</LinearLayout>