Open-sided Android stroke?

I achieved a good solution with this one:

<?xml version="1.0" encoding="utf-8"?>

<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
<!-- This is the line -->
    <item android:top="-1dp" android:right="-1dp" android:left="-1dp">
      <shape>
            <solid android:color="@android:color/transparent" />
            <stroke android:width="1dp" android:color="#ffffff" />
      </shape>
    </item>

</layer-list>

This works well in case you need a transparent background but still an open stroke color (In my case I only needed a bottom line). If you need a background color you can add a solid shape color as in Maragues answer.

EDIT 1

Sometimes, for High Density devices, using low dip values may end in very thin or invisible strokes or distances. This may happen to you also when setting ListView dividers.

The simplest workaround is to use a distance of 1px instead of 1dp. This will make the line always visible at all densities. The best solution would be to create dimension resources for each density, to get the best size for each device.

Edit 2

Fun, but I tried to use this 6 years later and I can't get a good result on Lollipop devices.

Probably the current solution is to use 9-patch. Android should have made an easy solution for this problem after all this time.

I know this question was posted long ago, so the answer will not be used by the person who posted this question, but it may still help others.

 <?xml version="1.0" encoding="UTF-8"?>
    <!-- inset is used to remove border from top, it can remove border from any other side-->
    <inset xmlns:android="http://schemas.android.com/apk/res/android"
        android:insetTop="-2dp"
        >
    <shape xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/rectangle">
        <stroke android:width="1dp" android:color="#b7b7b7" />
        <corners android:bottomRightRadius="5dp"  android:bottomLeftRadius="5dp"/>

        <solid android:color="#454444"/>
    </shape>
    </inset>

Use the inset tag and give a negative value for the side border you want to remove.

The possible values are:

android:insetTop="-1dp" android:insetBottom="-1dp" android:insetLeft="-1dp" android:insetRight="-1dp"

I solved this by using a list-layer, combining two shapes, one of which with height 1dp placed at the bottom

optionscreen_bottomrectangle.xml:

<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
<!-- This is the line -->
<item>
      <shape>
            <solid android:color="#535353" />
      </shape>
</item>
<!-- This is the main color -->
<item android:bottom="1dp">
     <shape>
           <solid android:color="#252525" />
     </shape>
</item>
</layer-list>

Then, in the layout/main.xml file

<TextView
    android:id="@+id/bottom_rectangle"
    android:background="@drawable/optionscreen_bottomrectangle"
    android:layout_width="fill_parent"
    android:layout_height="0dp"
    android:layout_below="@id/table_options"
    android:layout_above="@id/exit_bar"/>

Which fills the gap between table_options and exit_bar with a background and just before exit_bar prints a 1dp line. This did the trick for me, I hope it helps someone else.

Answer edited to place layers in the correct order. Thx Alex!