Transparent button bars found in Android Gallery App

I am trying to add a transparent button bars at the top and bottom of my activity, much like in the Android Gallery App.

I have been looking through the Gallery app source code, but I'm not able to see ho开发者_如何学Cw they did it. When using some snippits of their code, I am able to produce a button bar, but it is a dark grey color with lighter grey buttons:

<LinearLayout android:id="@+id/gridView_multiSelectBar"
    android:orientation="horizontal" android:visibility="gone"
    android:layout_width="match_parent" android:layout_height="wrap_content"
    android:layout_weight="0" android:clickable="false"
    android:paddingTop="5dp" android:paddingLeft="4dp"
    android:paddingRight="4dp" android:paddingBottom="1dp"
    android:background="@android:drawable/bottom_bar"
    android:layout_alignParentBottom="true">

    <Button android:id="@+id/gridView_multiSelectBar_button_share"
        android:layout_width="0dp" android:layout_height="match_parent"
        android:layout_weight="1" android:text="@string/gridView_multiSelectBar_button_share" />

    <Button android:id="@+id/gridView_multiSelectBar_button_copy"
        android:layout_width="0dp" android:layout_height="match_parent"
        android:layout_weight="1" android:text="@string/gridView_multiSelectBar_button_copy" />

    <Button android:id="@+id/gridView_multiSelectBar_button_delete"
        android:layout_width="0dp" android:layout_height="match_parent"
        android:layout_weight="1" android:text="@string/gridView_multiSelectBar_button_delete" />

    <Button android:id="@+id/gridView_multiSelectBar_button_close"
        android:layout_width="0dp" android:layout_height="match_parent"
        android:layout_weight="1" android:text="@string/gridView_multiSelectBar_button_close" />
</LinearLayout>

The code implies that they are using Button widgets. The screenshot below almost looks like its using a menu for the bottom, but then I'm not sure how they are drawing the top area.

My app has a black background. I would like these buttons to a thin border to show the boundaries between them, as well as the main content.

Can anyone can point me in the right direction?

Thanks in advance, Kevin

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A similar question was asked and answered in How to Set Opacity (Alpha) for View in Android. It is a matter of setting the alpha content of your view. Hope that helps you.

Cheers!!!
nJoshi