android layout: how to write this one?
<p>I want an activity with below layout:</p>

<pre><code>top button
middle(scroll view)
bottom button
</code></pre>

<p>I want the bottom button to attach to the bottom of the activity view, and the middle part occupies the rest of the space.</p>

<p>How I can write the layout xml file?</p>

<p>Below doesn't work:</p>

<pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
&lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent" android:layout_height="fill_parent"&gt;
    &lt;LinearLayout android:focusable="true"
        android:focusableInTouchMode="true" android:layout_width="0px"
        android:layout_height="0px" /&gt;

    &lt;LinearLayout android:orientation="vertical"
        android:layout_width="fill_parent" android:weightSum="1" android:layout_height="wrap_content"&gt;

        &lt;LinearLayout android:orientation="horizontal"
            android:layout_width="fill_parent" android:layout_height="wrap_content"
            android:weightSum="1"&gt;
            &lt;EditText android:id="@+id/edit_search"
                android:layout_width="wrap_content" android:layout_height="wrap_content"
                android:lines="1" android:hint="发微博内容" android:layout_weight="0.9" /&gt;
            &lt;Button android:layout_height="wrap_content" android:text="Search"
                android:layout_width="wrap_content" android:id="@+id/search_btn"
                android:layout_weight="0.1"&gt;&lt;/Button&gt;
        &lt;/LinearLayout&gt;

        &lt;TextView android:layout_width="fill_parent"
            android:layout_height="wrap_content" android:id="@+id/TextView01"
            android:paddingTop="5dip" /&gt;
        &lt;ListView android:layout_width="fill_parent"
            android:id="@+id/lv01" android:layout_height="390dp"&gt;
        &lt;/ListView&gt;
        &lt;Button android:id="@+id/create_new_btn" 
        android:layout_height="wrap_content" android:text="我要评论" android:layout_gravity="bottom"
        android:layout_width="fill_parent"&gt;&lt;/Button&gt;
    &lt;/LinearLayout&gt;

&lt;/LinearLayout&gt;
</code></pre>
