Spinner inside GridLayout

Question

Adding a Spinner to a GridLayout seems to "break" the layout. I have prepared a minimal working example to illustrate the issue:

I want a grid with labels on the left and input controls on the right. The controls on the right should take up the remaining space. This is what a simple example looks like:

Replacing one of the input controls with a spinner causes the right column to extend out of the screen boundaries, leading to an ugly layout.

Why does this happen, and how can I avoid it?

---

Here's the code of the first example:

<?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="2" >

    <TextView
        android:layout_gravity="left"
        android:text="TextView" />

    <EditText
        android:layout_gravity="fill_horizontal"
        android:hint="EditText" />

    <TextView
        android:layout_gravity="left"
        android:text="TextView" />

    <EditText
        android:layout_gravity="fill_horizontal"
        android:hint="EditText" />

</GridLayout>

And here's the code for the second image. The only difference is that the first EditText has been replaced by a Spinner:

<?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="2" >

    <TextView
        android:layout_gravity="left"
        android:text="TextView" />

    <Spinner
        android:id="@+id/spinner1"
        android:layout_gravity="fill_horizontal" />

    <TextView
        android:layout_gravity="left"
        android:text="TextView" />

    <EditText
        android:layout_gravity="fill_horizontal"
        android:hint="EditText" />

</GridLayout>

Answer 1

Apparently, the problem can be avoided by setting the layout_width of the Spinner to zero:

<Spinner 
    android:id="@+id/Spinner1"
    android:layout_gravity="fill_horizontal"
    android:layout_width="0dp" />

I'll mark this as the accepted answer, since it fixes the problem easily, but I'll gladly change that if someone can come up with an explanation for this behaviour.