android:layout_weight beginner's question

Question

When I have the following, it shows top layout with four colors has much smaller area than the bottom layout area.

According to http://developer.android.com/guide/topics/ui/layout-objects.html#linearlayout, when you add more to layout_weight, it should increase the area, but it decreases in the code.

Any help will be appreciated.

Thanks in advance.

<?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="4">
      <TextView
          android:text="red"
          android:gravity="center_horizontal"
          android:background="#aa0000"
          android:layout_width="wrap_content"
          android:layout_height="fill_parent"
          android:layout_weight="3"/>
      <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>

Answer 1

If you are using fill_parent in a LinearLayout the layout will take as much space as possible and all layout items defined later will have to deal with the space left.

If you set the height of both of you LinearLayouts to wrap_content the weight should work as documented.

Answer 2

Building on what Janusz said, if you use fill_parent, you can then set android:layout_weight to "split" the "full area" between multiple layout items.

The layout_weight doesn't increase the area, it increases it "right" to the area. but it's also relative to the parent. If you have a parent with a layout_height=fill_parent, with a layout_weight=0 and the parent has a sibling with the same, setting layout_weight=1 to one of the children does not affect the parent.

Both the parent, and the sibling, would take up 50% of the available area that they can fill.