Linear Layout and weight in Android

Question

3 things to remember:

• set the android:layout_width of the children to "0dp"
• set the android:weightSum of the parent (edit: as Jason Moore noticed, this attribute is optional, because by default it is set to the children's layout_weight sum)
• set the android:layout_weight of each child proportionally (e.g. weightSum="5", three children: layout_weight="1", layout_weight="3", layout_weight="1")

Example:

<LinearLayout
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:weightSum="5">

    <Button
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="1" />

    <Button
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="3"
        android:text="2" />

    <Button
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="3" />

</LinearLayout>

And the result:

You are not setting the layout_weight property. Your code reads weight="1" and it should read android:layout_weight="1".

It's android:layout_weight. Weight can only be used in LinearLayout. If the orientation of linearlayout is Vertical, then use android:layout_height="0dp" and if the orientation is horizontal, then use android:layout_width = "0dp". It'll work perfectly.

This image summarizes the Linear layout.

You can follow this link for more information on the topic. Just Maths - Views, View Groups and Layouts

Video Tutorial For Linear Layout : Width, Height & Weights

Android Linear Layout Tutorial

Try setting the layout_width of both buttons to "0dip" and the weight of both buttons to 0.5

LinearLayout supports assigning a weight to individual children. This attribute assigns an "importance" value to a view, and allows it to expand to fill any remaining space in the parent view. Default weight is zero

calculation to assign any Remaining/Extra space between child. (not the total space)

space assign to child = (child individual weight) / (sum of weight of every child in Linear Layout)

Example (1): if there are three text boxes and two of them declare a weight of 1, while the third one is given no weight (0), then Remaining/Extra space assign to

1st text box = 1/(1+1+0) 
2nd text box = 1/(1+1+0) 
3rd text box = 0/(1+1+0) 

Example (2) : let's say we have a text label and two text edit elements in a horizontal row. The label has no layout_weight specified, so it takes up the minimum space required to render. If the layout_weight of each of the two text edit elements is set to 1, the remaining width in the parent layout will be split equally between them (because we claim they are equally important).

calculation : 
1st label = 0/(0+1+1) 
2nd text box = 1/(0+1+1) 
3rd text box = 1/(0+1+1)

If the first one text box has a layout_weight of 1 and the second text box has a layout_weight of 2, then one third of the remaining space will be given to the first, and two thirds to the second (because we claim the second one is more important).

calculation : 
1st label = 0/(0+1+2) 
2nd text box = 1/(0+1+2) 
3rd text box = 2/(0+1+2)