On the GridLayout you can set the rowCount and columnCount to 3 and for each ImageView, set the rowWeight and columnWeight to 1.
As for the spacing, you can set a layout_margin for each off the ImageView so they ware evenly spaced.
<?xml version="1.0" encoding="utf-8"?>
<GridLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:columnCount="3"
android:rowCount="3"
android:orientation="horizontal"
android:background="#CCCCCc">
<ImageView
android:layout_rowWeight="1"
android:layout_columnWeight="1"
android:layout_gravity="fill"
android:layout_margin="4dp"
android:background="#FFFFFF"
android:src="@drawable/image"
/>
<ImageView
android:layout_rowWeight="1"
android:layout_columnWeight="1"
android:layout_gravity="fill"
android:layout_margin="4dp"
android:background="#FFFFFF"
android:src="@drawable/image"
/>
<ImageView
android:layout_rowWeight="1"
android:layout_columnWeight="1"
android:layout_gravity="fill"
android:layout_margin="4dp"
android:background="#FFFFFF"
android:src="@drawable/image"
/>
<ImageView
android:layout_rowWeight="1"
android:layout_columnWeight="1"
android:layout_gravity="fill"
android:layout_margin="4dp"
android:background="#FFFFFF"
android:src="@drawable/image"
/>
<ImageView
android:layout_rowWeight="1"
android:layout_columnWeight="1"
android:layout_gravity="fill"
android:layout_margin="4dp"
android:background="#FFFFFF"
android:src="@drawable/image"
/>
<ImageView
android:layout_rowWeight="1"
android:layout_columnWeight="1"
android:layout_gravity="fill"
android:layout_margin="4dp"
android:background="#FFFFFF"
android:src="@drawable/image"
/>
<ImageView
android:layout_rowWeight="1"
android:layout_columnWeight="1"
android:layout_gravity="fill"
android:layout_margin="4dp"
android:background="#FFFFFF"
android:src="@drawable/image"
/>
<ImageView
android:layout_rowWeight="1"
android:layout_columnWeight="1"
android:layout_gravity="fill"
android:layout_margin="4dp"
android:background="#FFFFFF"
android:src="@drawable/image"
/>
<ImageView
android:layout_rowWeight="1"
android:layout_columnWeight="1"
android:layout_gravity="fill"
android:layout_margin="4dp"
android:background="#FFFFFF"
android:src="@drawable/image"
/>
</GridLayout>