Android: strange weight inversion in LinearLayout

Question

This is the xml layout i'm working on:

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

    <ScrollView 
        android:layout_weight="2" 
        android:id="@+id/scrollConfirm" 
        android:layout_width="fill_parent"
        android:layout_height="fill_parent">

  </ScrollView>

  <LinearLayout 
      android:layout_marginTop="20px"
      android:layout_weight="1" 
      android:id="@+id/imageNumpad" 
      android:orientation="vertical" 
      android:layout_width="fill_parent" 
      android:layout_height="fill_parent">
        <ImageView android:src="@drawable/myicon"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_gravity="bottom"
            android:background="#FFFFFF"
        />
   </LinearLayout>
</LinearLayout>

Since I have setted the ScrollView with layout_weight="2" and the LinearLayout (child) with layout_weight="1" I expected that the ScrollView will use up twice free space that the LinearLayout. But I obtain the opposite result. The ScrollView is smaller than LinearLayout. Whereas if I set for the ScrollView layout_weight="1" and LinearLayout with layout_weight="2", the ScrollView is greater than LinearLayou.

How is this possible??

Answer 1

Weight get inverse because you are using match_parent as the layout_height. The weight is used to distribute the remaining empty space or take away space when the total sum is larger than the LinearLayout. Set your heights to 0dip it will work.

i.e., set layout_height = "0dip" for both ScrollView and inner LinearLayout.

Reference :

The use of layout_weight with Android layouts