Android layout issue - relative widths in percent using weight

I am trying to assign relative widths to columns in a ListView that is in a TabHost, using layout_weight as suggested here:

<?xml version="1.0" encoding="utf-8"?>
<TabHost xmlns:android="http://schemas.android.com/apk/res/android"
  android:id="@android:id/tabhost"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent">
  <LinearLayout
     android:orientation="vertical"
     android:layout_width="fill_parent"
     android:layout_height="fill_parent">
     <TabWidget android:id="@android:id/tabs"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"/>
        <FrameLayout android:id="@android:id/tabcontent"
           android:layout_width="fill_parent"
           android:layout_height="fill_parent">
           <TableLayout  
              android:id="@+id/triplist" 
              android:layout_width="fill_parent"
              android:layout_height="wrap_content"
              android:paddingTop="4px">
              <TableRow>
                 <ListView android:id="@+id/triplistview"
                    android:layout_width="fill_parent"
                    android:layout_height="wrap_content"/>
              </TableRow>
              <TableRow>
                 <Button android:id="@+id/newtripbutton"
                    android:layout_width="wrap_content"
                  开发者_运维百科  android:layout_height="wrap_content"
                    android:text="Add Trip"/>
              </TableRow>
[other tabs ...]

My row definition has 4 columns that I would like to size as follows:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   android:orientation="horizontal"
   android:weightSum="1.0"
   android:padding="4px">   
   <TextView android:id="@+id/rowtripdate"
      android:layout_weight=".2"
      android:layout_width="0dip"
      android:layout_height="wrap_content"
      android:inputType="date"/>
   <TextView android:id="@+id/rowodostart"
      android:layout_weight=".2"
      android:layout_width="0dip"
      android:layout_height="wrap_content"/>
   <TextView android:id="@+id/rowodoend"
      android:layout_weight=".2"
      android:layout_width="0dip"
      android:layout_height="wrap_content"/>
   <TextView android:id="@+id/rowcomment"
      android:layout_weight=".4"
      android:layout_width="0dip"
      android:layout_height="wrap_content">

Unfortunately, it seems to want to fit all the columns into the space that the button occupies, as opposed to the width of the screen. Or maybe there is another constraint that I do not understand. I'd appreciate your help.

_{(source: heeroz.com)}

I think I forgot this property for the TableLayout element:

android:stretchColumns="0"

It appears to be working now.

I don't see anything obviously wrong in what you are showing there. To get a better picture of what is going on, you might try out the heirarchy viewer. It comes with the SDK. It will visualize for you how much space each of the "hidden" layers is taking, so you can figure out which one decided to only be that big.