android底部菜单的按钮

<RelativeLayout
    android:id="@+id/btn_container_conversation"
    android:layout_width="0dp"
    android:layout_height="match_parent"
    android:layout_weight="1" >

    <Button
        android:id="@+id/btn_conversation"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@drawable/em_main_bottom_item_bg"
        android:drawableTop="@drawable/em_tab_chat_bg"
        android:onClick="onTabClicked"
        android:paddingBottom="2dip"
        android:paddingTop="7dip"
        android:scaleType="matrix"
        android:text="@string/session"
        android:textColor="@color/em_main_botton_text_color"
        android:textSize="12sp" />

    <TextView
        android:id="@+id/unread_msg_number"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:layout_marginRight="10dp"
        android:layout_marginTop="1dp"
        android:background="@drawable/em_unread_count_bg"
        android:gravity="center"
        android:textColor="@android:color/white"
        android:textSize="12sp"
        android:visibility="invisible" />
</RelativeLayout>