1page.title=Linear Layout
2page.tags=linearlayout
3@jd:body
4
5<div id="qv-wrapper">
6<div id="qv">
7<h2>In this document</h2>
8<ol>
9  <li><a href="#Weight">Layout Weight</a></li>
10  <li><a href="#Example">Example</a></li>
11</ol>
12
13<h2>Key classes</h2>
14<ol>
15  <li>{@link android.widget.LinearLayout}</li>
16  <li>{@link android.widget.LinearLayout.LayoutParams}</li>
17</ol>
18</div>
19</div>
20
21<p>{@link android.widget.LinearLayout} is a view group that aligns all children in a single
22direction, vertically or horizontally. You can specify the layout direction with the
23<a href="{@docRoot}reference/android/widget/LinearLayout.html#attr_android:orientation">{@code
24android:orientation}</a> attribute.</p>
25
26<img src="{@docRoot}images/ui/linearlayout.png" alt="" />
27
28<p>All children of a {@link android.widget.LinearLayout} are
29stacked one after the other, so a vertical list will only have one child per
30row, no matter how wide they are, and a horizontal list will only be one row
31high (the height of the tallest child, plus padding). A {@link
32android.widget.LinearLayout LinearLayout} respects <em>margin</em>s between children
33and the <em>gravity</em> (right, center, or left alignment) of each child. </p>
34
35
36<h2 id="Weight">Layout Weight</h2>
37
38<div class="sidebox-wrapper">
39<div class="sidebox">
40  <h3>Equally weighted children</h3>
41<p>To create a linear layout in which each child uses the same amount of
42space on the screen, set the <a
43href="{@docRoot}reference/android/view/ViewGroup.LayoutParams.html#attr_android:layout_height"
44>{@code android:layout_height}</a> of each view to {@code "0dp"} (for a
45vertical layout) or the <a
46href="{@docRoot}reference/android/view/ViewGroup.LayoutParams.html#attr_android:layout_width"
47>{@code android:layout_width}</a> of each view to {@code "0dp"} (for a
48horizontal
49layout). Then set the <a
50href="{@docRoot}reference/android/widget/LinearLayout.LayoutParams.html#attr_android:layout_weight"
51>{@code android:layout_weight}</a> of each view to {@code "1"}.</p>
52</div>
53</div>
54
55
56<p>{@link android.widget.LinearLayout} also supports assigning a
57<em>weight</em> to individual children with the <a
58href="{@docRoot}reference/android/widget/LinearLayout.LayoutParams.html#attr_android:layout_weight"
59>{@code android:layout_weight}</a> attribute.
60This attribute assigns an "importance" value to a view in
61terms of how much space is should occupy on the screen. A larger weight value allows it to expand
62to fill any remaining space in the parent view.
63Child views can specify a weight value, and then any remaining space in the view group is
64assigned to children in the proportion of their declared weight. Default
65weight is zero.</p>
66
67<p>For example, if there are three text fields and two of them declare a weight of 1, while the
68other is given no weight, the third text field without weight will not grow and will only occupy the
69area required by its content. The other two will expand equally to fill the space remaining after
70all three fields are measured. If the third field is then given a weight of 2 (instead of 0), then
71it is now declared more important than both the others, so it gets half the total remaining space,
72while the first two
73share the rest equally.</p>
74
75
76<h2 id="Example">Example</h2>
77
78<div class="figure" style="width:220px;margin-top:0">
79<img src="{@docRoot}images/ui/sample-linearlayout.png" alt="" />
80</div>
81
82<pre>
83&lt;?xml version="1.0" encoding="utf-8"?>
84&lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
85    android:layout_width="match_parent"
86    android:layout_height="match_parent"
87    android:paddingLeft="16dp"
88    android:paddingRight="16dp"
89    android:orientation="vertical" >
90    &lt;EditText
91        android:layout_width="match_parent"
92        android:layout_height="wrap_content"
93        android:hint="@string/to" />
94    &lt;EditText
95        android:layout_width="match_parent"
96        android:layout_height="wrap_content"
97        android:hint="@string/subject" />
98    &lt;EditText
99        android:layout_width="match_parent"
100        android:layout_height="0dp"
101        android:layout_weight="1"
102        android:gravity="top"
103        android:hint="@string/message" />
104    &lt;Button
105        android:layout_width="100dp"
106        android:layout_height="wrap_content"
107        android:layout_gravity="right"
108        android:text="@string/send" />
109&lt;/LinearLayout>
110</pre>
111
112<p>For details about the attributes available to each child view of a {@link
113android.widget.LinearLayout}, see {@link android.widget.LinearLayout.LayoutParams}.</p>
114
115
116