Why does the LinearLayout attribute "layout_weight" seem to do the opposite of what I think it should do?

Question

I'm following this tutorial to learn about linear layouts. Here's the main layout file:

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

  <LinearLayout
      android:orientation="horizontal"
      android:layout_width="fill_parent"
      android:layout_height="fill_parent"
      android:layout_weight="1">
      <TextView
          android:text="red"
          android:gravity="center_horizontal"
          android:background="#aa0000"
          android:layout_width="wrap_content"
          android:layout_height="fill_parent"
          android:layout_weight="1"/>
      <TextView
          android:text="green"
          android:gravity="center_horizontal"
          android:background="#00aa00"
          android:layout_width="wrap_content"
          android:layout_height="fill_parent"
          android:layout_weight="1"/>
      <TextView
          android:text="blue"
          android:gravity="center_horizontal"
          android:background="#0000aa"
          android:layout_width="wrap_content"
          android:layout_height="fill_parent"
          android:layout_weight="1"/>
      <TextView
          android:text="yellow"
          android:gravity="center_horizontal"
          android:background="#aaaa00"
          android:layout_width="wrap_content"
          android:layout_height="fill_parent"
          android:layout_weight="1"/>
  </LinearLayout>

  <LinearLayout
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:layout_weight="1">
    <TextView
        android:text="row one"
        android:textSize="15pt"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"/>
    <TextView
        android:text="row two"
        android:textSize="15pt"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"/>
    <TextView
        android:text="row three"
        android:textSize="15pt"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"/>
    <TextView
        android:text="row four"
        android:textSize="15pt"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"/>
  </LinearLayout>

</LinearLayout>

Which produces this:

linear layout example

I was experimenting with trying to make the colored bars at the top (the first child of the layout) vertically twice as big as the horizontal rows at the bottom (the last child) by making the first child's layout weight twice the second child's:

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

  <LinearLayout
      android:orientation="horizontal"
      android:layout_width="fill_parent"
      android:layout_height="fill_parent"
      android:layout_weight="2">
      <TextView
          android:text="red"
          android:gravity="center_horizontal"
          android:background="#aa0000"
          android:layout_width="wrap_content"
          android:layout_height="fill_parent"
          android:layout_weight="1"/>
      <TextView
          android:text="green"
          android:gravity="center_horizontal"
          android:background="#00aa00"
          android:layout_width="wrap_content"
          android:layout_height="fill_parent"
          android:layout_weight="1"/>
      <TextView
          android:text="blue"
          android:gravity="center_horizontal"
          android:background="#0000aa"
          android:layout_width="wrap_content"
          android:layout_height="fill_parent"
          android:layout_weight="1"/>
      <TextView
          android:text="yellow"
          android:gravity="center_horizontal"
          android:background="#aaaa00"
          android:layout_width="wrap_content"
          android:layout_height="fill_parent"
          android:layout_weight="1"/>
  </LinearLayout>

  <LinearLayout
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:layout_weight="1">
    <TextView
        android:text="row one"
        android:textSize="15pt"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"/>
    <TextView
        android:text="row two"
        android:textSize="15pt"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"/>
    <TextView
        android:text="row three"
        android:textSize="15pt"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"/>
    <TextView
        android:text="row four"
        android:textSize="15pt"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"/>
  </LinearLayout>

</LinearLayout>

But this does the opposite of my expected result: it actually makes the colored bars vertically smaller by about half.

The android developer docs specify that

any remaining space in the view group is assigned to children in the proportion of their declared weight

Why does it seem like the inverse is true?

It is ACTUALLY reverse.The one which you want to be bigger should be given lesser number as weight. — Hiral Vadodaria, Dec 05 '11 at 04:34
@Hiral care to back that up? Is that always true or only when you use `fill_parent`? I know the opposite is true when you give the competing views zero space to begin with — skynet, Dec 05 '11 at 14:25
@Craigy: actually i don't know what behavior it persist exactly with various cases.but almost everytime,it acts opposite as i described.but yes,sometime it acts differently.I didnt know the reason at that time.but now i think,fill_parent might be affecting its behavior as you said. — Hiral Vadodaria, Dec 06 '11 at 04:11
For more recent visitors, `fill_parent` is now deprecated. Use `match_parent` instead. — Snowcrash, Oct 08 '13 at 04:44
possible duplicate of [android:layout\_weight beginner's question](http://stackoverflow.com/questions/3084185/androidlayout-weight-beginners-question) — ben75, Jun 24 '14 at 23:30

score 10 · Answer 1 · answered Dec 05 '11 at 04:31

10

Emphasis on any remaining space...

I think it is a conflict between using fill_parent for height and the layout weight. Try setting android:layout_height="0dp" for both LinearLayouts.

answered Dec 05 '11 at 04:31

skynet

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score 5 · Answer 2 · answered Dec 05 '11 at 05:50

layout_weight is normally used with layout_width or layout_height set to wrap_content. Try it, you'll see that it then increases the layout sized based on which view has the higher weight.

Example

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">

  <LinearLayout
      android:orientation="horizontal"
      android:layout_width="fill_parent"
      android:layout_height="wrap_content"
      android:layout_weight="2">
      <TextView
          android:text="red"
          android:gravity="center_horizontal"
          android:background="#aa0000"
          android:layout_width="wrap_content"
          android:layout_height="fill_parent"
          android:layout_weight="1"/>

  </LinearLayout>

  <LinearLayout
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_weight="1">
    <TextView
        android:text="row one"
        android:textSize="15pt"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"/>

  </LinearLayout>

</LinearLayout>

score 3 · Answer 3 · answered Dec 05 '11 at 07:48

<?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" android:weightSum="3">

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="0dp"
        android:layout_weight="2"
        android:orientation="horizontal" >

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:background="#aa0000"
            android:gravity="center_horizontal"
            android:text="red" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:background="#00aa00"
            android:gravity="center_horizontal"
            android:text="green" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:background="#0000aa"
            android:gravity="center_horizontal"
            android:text="blue" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="fill_parent"
            android:layout_weight="1"
            android:background="#aaaa00"
            android:gravity="center_horizontal"
            android:text="yellow" />
    </LinearLayout>

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:orientation="vertical" >

        <TextView
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="row one"
            android:textSize="15pt" />

        <TextView
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="row two"
            android:textSize="15pt" />

        <TextView
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="row three"
            android:textSize="15pt" />

        <TextView
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="row four"
            android:textSize="15pt" />
    </LinearLayout>

</LinearLayout>

enter image description here

Specify android:weightSum for the parent layout and also android:layout_height="0dp" for child layouts. Please try this. Hope this would help.

The answer was helpful. But it seems like you don't need the android:weightSum specified. According to android documentation: "If unspecified, the sum is computed by adding the layout_weight of all of the children." — Aishwar, Mar 04 '12 at 00:20

Why does the LinearLayout attribute "layout_weight" seem to do the opposite of what I think it should do?

3 Answers3

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