android - Buttons aren't shown in the LinearLayout -

i want looks (this screenshot graphical layout editor):

so created layout:

<?xml version="1.0" encoding="utf-8"?> <linearlayout xmlns:android="http://schemas.android.com/apk/res/android"     android:layout_width="match_parent"     android:layout_height="match_parent"     android:orientation="vertical" >      <linearlayout         android:id="@+id/controls"         android:layout_width="match_parent"         android:layout_height="wrap_content"         android:orientation="horizontal" >          <button             android:id="@+id/clearbutton"             android:layout_width="wrap_content"             android:layout_height="match_parent"             android:text="@string/clearbuttontext"             android:layout_weight="1"              />          <edittext             android:id="@+id/searchtext"             android:layout_width="wrap_content"             android:layout_height="match_parent"             android:layout_weight="5"             android:hint="@string/defaultsearchtext"             >              <requestfocus/>         </edittext>          <button             android:id="@+id/addbutton"             android:layout_width="wrap_content"             android:layout_height="match_parent"             android:text="@string/addbuttontext"             android:layout_weight="1"              />     </linearlayout>      <listview         android:id="@+id/list_view"         android:layout_width="match_parent"         android:layout_height="wrap_content"         android:layout_weight="1" />  </linearlayout> 

but when ran app on emulator saw:

when clicked on loupe there still no sign of buttons.

i think should use weights width of elements of horizontal layout. means width of elements weight should 0dp

<linearlayout     android:id="@+id/controls"     android:layout_width="match_parent"     android:layout_height="wrap_content"     android:orientation="horizontal" >      <button         android:id="@+id/clearbutton"         android:layout_width="0dp"         android:layout_weight="0.2"         android:layout_height="match_parent"         android:text="@string/clearbuttontext"          />      <edittext         android:id="@+id/searchtext"         android:layout_width="0dp"         android:layout_weight="0.6"         android:layout_height="match_parent"         android:hint="@string/defaultsearchtext"         >          <requestfocus/>     </edittext>      <button         android:id="@+id/addbutton"         android:layout_width="0dp"         android:layout_weight="0.3"         android:layout_height="match_parent"         android:text="@string/addbuttontext"         /> </linearlayout>