Home | History | Annotate | Download | only in layout 
      1 page.title=Linear Layout
      2 page.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
     22 direction, vertically or horizontally. You can specify the layout direction with the
     23 <a href="{@docRoot}reference/android/widget/LinearLayout.html#attr_android:orientation">{@code
     24 android: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
     29 stacked one after the other, so a vertical list will only have one child per
     30 row, no matter how wide they are, and a horizontal list will only be one row
     31 high (the height of the tallest child, plus padding). A {@link
     32 android.widget.LinearLayout LinearLayout} respects <em>margin</em>s between children
     33 and 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
     42 space on the screen, set the <a
     43 href="{@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
     45 vertical layout) or the <a
     46 href="{@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
     48 horizontal
     49 layout). Then set the <a
     50 href="{@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
     58 href="{@docRoot}reference/android/widget/LinearLayout.LayoutParams.html#attr_android:layout_weight"
     59 >{@code android:layout_weight}</a> attribute.
     60 This attribute assigns an "importance" value to a view in
     61 terms of how much space is should occupy on the screen. A larger weight value allows it to expand
     62 to fill any remaining space in the parent view. 
     63 Child views can specify a weight value, and then any remaining space in the view group is
     64 assigned to children in the proportion of their declared weight. Default
     65 weight 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
     68 other is given no weight, the third text field without weight will not grow and will only occupy the
     69 area required by its content. The other two will expand equally to fill the space remaining after
     70 all three fields are measured. If the third field is then given a weight of 2 (instead of 0), then
     71 it is now declared more important than both the others, so it gets half the total remaining space,
     72 while the first two
     73 share 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="fill_parent"
     86     android:layout_height="fill_parent"
     87     android:paddingLeft="16dp"
     88     android:paddingRight="16dp"
     89     android:orientation="vertical" >
     90     &lt;EditText
     91         android:layout_width="fill_parent"
     92         android:layout_height="wrap_content"
     93         android:hint="@string/to" />
     94     &lt;EditText
     95         android:layout_width="fill_parent"
     96         android:layout_height="wrap_content"
     97         android:hint="@string/subject" />
     98     &lt;EditText
     99         android:layout_width="fill_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
    113 android.widget.LinearLayout}, see {@link android.widget.LinearLayout.LayoutParams}.</p>
    114 
    115 
    116