Preciso criar minha própria barra de ferramentas no aplicativo Android. Agora, fica assim:

Então você vê espaços entre os botões. Tentei colocar margem / preenchimento negativos nos botões, mas o espaço não desaparece

Aqui está o código do layout:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <ListView
        android:id="@+id/routes_list"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:layout_weight="0.5">
    </ListView>

    <TableRow
        android:id="@+id/toolbar"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_margin="0dp"
        android:padding="0dp" >

        <Button
            android:id="@+id/btn_routes"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_margin="0dp"
            android:layout_weight="0.2"
            android:layout_marginRight="-10dp"
            android:layout_marginLeft="-10dp"
            android:text="@string/routes"
            android:textSize="10dp" />

        <Button
            android:id="@+id/btn_places"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_margin="0dp"
            android:layout_weight="0.2"
            android:layout_marginRight="-10dp"
            android:layout_marginLeft="-10dp"
            android:textSize="10dp"
            android:text="@string/places" />

        <Button
            android:id="@+id/btn_events"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_margin="0dp"
            android:layout_weight="0.2"
            android:layout_marginRight="-10dp"
            android:layout_marginLeft="-10dp"
            android:textSize="10dp"
            android:text="@string/events" />

        <Button
            android:id="@+id/btn_about"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_margin="0dp"
            android:layout_weight="0.2"
            android:layout_marginRight="-10dp"
            android:layout_marginLeft="-10dp"
            android:text="@string/about"
            android:textSize="10dp" />

    </TableRow>

</LinearLayout>

Como remover espaço entre os botões?