1page.title=Relative Layout 2page.tags=relativelayout 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="#Position">Positioning Views</a></li> 10 <li><a href="#Example">Example</a></li> 11 </ol> 12 <h2>Key classes</h2> 13 <ol> 14 <li>{@link android.widget.RelativeLayout}</li> 15 <li>{@link android.widget.RelativeLayout.LayoutParams}</li> 16 </ol> 17</div> 18</div> 19 20<p>{@link android.widget.RelativeLayout} is a view group that displays child views in relative 21positions. The position of each view can be specified as relative to sibling elements (such as to 22the left-of or below another view) or in positions relative to the parent {@link 23android.widget.RelativeLayout} area (such as aligned to the bottom, left or center).</p> 24 25<img src="{@docRoot}images/ui/relativelayout.png" alt="" /> 26 27<p>A {@link android.widget.RelativeLayout} is a very powerful utility for designing a user interface 28because it can eliminate nested view groups and keep your layout hierarchy flat, which improves 29performance. If you find yourself using several nested {@link android.widget.LinearLayout} groups, 30you may be able to replace them with a single {@link android.widget.RelativeLayout}.</p> 31 32 33<h2 id="Position">Positioning Views</h2> 34 35<p>{@link android.widget.RelativeLayout} lets child views specify their position relative to the 36parent view or to each other (specified by ID). So you can align two elements by right border, or 37make one below another, centered in the screen, centered left, and so on. By default, all child 38views are drawn at the top-left of the layout, so you must define the position of each view 39using the various layout properties available from {@link 40android.widget.RelativeLayout.LayoutParams}.</p> 41 42<p>Some of the many layout properties available to views in a {@link android.widget.RelativeLayout} 43include:</p> 44<dl> 45 <dt><a 46href="{@docRoot}reference/android/widget/RelativeLayout.LayoutParams.html#attr_android:layout_alignParentTop" 47>{@code android:layout_alignParentTop}</a></dt> 48 <dd>If {@code "true"}, makes the top edge of this view match the top edge of the parent. </dd> 49 <dt><a 50href="{@docRoot}reference/android/widget/RelativeLayout.LayoutParams.html#attr_android:layout_centerVertical" 51>{@code android:layout_centerVertical}</a></dt> 52 <dd>If {@code "true"}, centers this child vertically within its parent.</dd> 53 <dt><a 54href="{@docRoot}reference/android/widget/RelativeLayout.LayoutParams.html#attr_android:layout_below" 55>{@code android:layout_below}</a></dt> 56 <dd>Positions the top edge of this view below the view specified with a resource ID.</dd> 57 <dt><a 58href="{@docRoot}reference/android/widget/RelativeLayout.LayoutParams.html#attr_android:layout_toRightOf" 59>{@code android:layout_toRightOf}</a></dt> 60 <dd>Positions the left edge of this view to the right of the view specified with a resource ID.</dd> 61</dl> 62 63<p>These are just a few examples. All layout attributes are documented at {@link 64android.widget.RelativeLayout.LayoutParams}.</p> 65 66<p>The value for each layout property is either a boolean to 67enable a layout position relative to the parent {@link android.widget.RelativeLayout} or an ID that 68references another view in the layout against which the view should be positioned.</p> 69 70<p>In your XML layout, dependencies against other views in the layout can be declared in any order. 71For example, you can declare that "view1" be positioned below "view2" even if "view2" is the last 72view declared in the hierarchy. The example below demonstrates such a scenario.</p> 73 74 75<h2 id="Example">Example</h2> 76 77<p>Each of the attributes that control the relative position of each view are emphasized.</p> 78<div class="figure" style="width:220px;margin-top:0"> 79<img src="{@docRoot}images/ui/sample-relativelayout.png" alt="" /> 80</div> 81 82<pre> 83<?xml version="1.0" encoding="utf-8"?> 84<RelativeLayout 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 <EditText 90 android:id="@+id/name" 91 android:layout_width="match_parent" 92 android:layout_height="wrap_content" 93 android:hint="@string/reminder" /> 94 <Spinner 95 android:id="@+id/dates" 96 android:layout_width="0dp" 97 android:layout_height="wrap_content" 98 <strong>android:layout_below="@id/name"</strong> 99 <strong>android:layout_alignParentLeft="true"</strong> 100 <strong>android:layout_toLeftOf="@+id/times"</strong> /> 101 <Spinner 102 android:id="@id/times" 103 android:layout_width="96dp" 104 android:layout_height="wrap_content" 105 <strong>android:layout_below="@id/name"</strong> 106 <strong>android:layout_alignParentRight="true"</strong> /> 107 <Button 108 android:layout_width="96dp" 109 android:layout_height="wrap_content" 110 <strong>android:layout_below="@id/times"</strong> 111 <strong>android:layout_alignParentRight="true"</strong> 112 android:text="@string/done" /> 113</RelativeLayout> 114</pre> 115 116<p>For details about all the layout attributes available to each child view of a {@link 117android.widget.RelativeLayout}, see {@link android.widget.RelativeLayout.LayoutParams}.</p> 118
