Home | History | Annotate | Download | only in layout 
      1 page.title=Linear Layout
      2 parent.title=Layouts
      3 parent.link=layout-objects.html
      4 @jd:body
      5 
      6 <div id="qv-wrapper">
      7 <div id="qv">
      8 <h2>In this document</h2>
      9 <ol>
     10   <li><a href="#Weight">Layout Weight</a></li>
     11   <li><a href="#Example">Example</a></li>
     12 </ol>
     13 
     14 <h2>Key classes</h2>
     15 <ol>
     16   <li>{@link android.widget.LinearLayout}</li>
     17   <li>{@link android.widget.LinearLayout.LayoutParams}</li>
     18 </ol>
     19 </div>
     20 </div>
     21 
     22 <p>{@link android.widget.LinearLayout} is a view group that aligns all children in a single
     23 direction, vertically or horizontally. You can specify the layout direction with the
     24 <a href="{@docRoot}reference/android/widget/LinearLayout.html#attr_android:orientation">{@code
     25 android:orientation}</a> attribute.</p>
     26 
     27 <img src="{@docRoot}images/ui/linearlayout.png" alt="" />
     28 
     29 <p>All children of a {@link android.widget.LinearLayout} are
     30 stacked one after the other, so a vertical list will only have one child per
     31 row, no matter how wide they are, and a horizontal list will only be one row
     32 high (the height of the tallest child, plus padding). A {@link
     33 android.widget.LinearLayout LinearLayout} respects <em>margin</em>s between children
     34 and the <em>gravity</em> (right, center, or left alignment) of each child. </p>
     35 
     36 
     37 <h2 id="Weight">Layout Weight</h2>
     38 
     39 <div class="sidebox-wrapper">
     40 <div class="sidebox">
     41   <h3>Equally weighted children</h3>
     42 <p>To create a linear layout in which each child uses the same amount of
     43 space on the screen, set the <a
     44 href="{@docRoot}reference/android/view/ViewGroup.LayoutParams.html#attr_android:layout_height"
     45 >{@code android:layout_height}</a> of each view to {@code "0dp"} (for a
     46 vertical layout) or the <a
     47 href="{@docRoot}reference/android/view/ViewGroup.LayoutParams.html#attr_android:layout_width"
     48 >{@code android:layout_width}</a> of each view to {@code "0dp"} (for a
     49 horizontal
     50 layout). Then set the <a
     51 href="{@docRoot}reference/android/widget/LinearLayout.LayoutParams.html#attr_android:layout_weight"
     52 >{@code android:layout_weight}</a> of each view to {@code "1"}.</p>
     53 </div>
     54 </div>
     55 
     56 
     57 <p>{@link android.widget.LinearLayout} also supports assigning a
     58 <em>weight</em> to individual children with the <a
     59 href="{@docRoot}reference/android/widget/LinearLayout.LayoutParams.html#attr_android:layout_weight"
     60 >{@code android:layout_weight}</a> attribute.
     61 This attribute assigns an "importance" value to a view in
     62 terms of how much space is should occupy on the screen. A larger weight value allows it to expand
     63 to fill any remaining space in the parent view. 
     64 Child views can specify a weight value, and then any remaining space in the view group is
     65 assigned to children in the proportion of their declared weight. Default
     66 weight is zero.</p>
     67 
     68 <p>For example, if there are three text fields and two of them declare a weight of 1, while the
     69 other is given no weight, the third text field without weight will not grow and will only occupy the
     70 area required by its content. The other two will expand equally to fill the space remaining after
     71 all three fields are measured. If the third field is then given a weight of 2 (instead of 0), then
     72 it is now declared more important than both the others, so it gets half the total remaining space,
     73 while the first two
     74 share the rest equally.</p>
     75 
     76 
     77 <h2 id="Example">Example</h2>
     78 
     79 <div class="figure" style="width:220px;margin-top:0">
     80 <img src="{@docRoot}images/ui/sample-linearlayout.png" alt="" />
     81 </div>
     82 
     83 <pre>
     84 &lt;?xml version="1.0" encoding="utf-8"?>
     85 &lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     86     android:layout_width="fill_parent"
     87     android:layout_height="fill_parent"
     88     android:paddingLeft="16dp"
     89     android:paddingRight="16dp"
     90     android:orientation="vertical" >
     91     &lt;EditText
     92         android:layout_width="fill_parent"
     93         android:layout_height="wrap_content"
     94         android:hint="@string/to" />
     95     &lt;EditText
     96         android:layout_width="fill_parent"
     97         android:layout_height="wrap_content"
     98         android:hint="@string/subject" />
     99     &lt;EditText
    100         android:layout_width="fill_parent"
    101         android:layout_height="0dp"
    102         android:layout_weight="1"
    103         android:gravity="top"
    104         android:hint="@string/message" />
    105     &lt;Button
    106         android:layout_width="100dp"
    107         android:layout_height="wrap_content"
    108         android:layout_gravity="right"
    109         android:text="@string/send" />
    110 &lt;/LinearLayout>
    111 </pre>
    112 
    113 <p>For details about the attributes available to each child view of a {@link
    114 android.widget.LinearLayout}, see {@link android.widget.LinearLayout.LayoutParams}.</p>
    115 
    116 
    117