practices/ui_guidelines/widget_design.jd

page.title=App Widget Design Guidelines
parent.title=UI Guidelines
parent.link=index.html
@jd:body

<div id="qv-wrapper">
<div id="qv">

<h2>Quickview</h2>

<ul>
  <li>App Widget layouts should be flexible, resizing to fit their parent container</li>
  <li>As of Android 3.0, app widgets can depict collections of items and provide a representative
    preview image for the widget gallery</li>
  <li>As of Android 3.1, app widgets can be resizable horizontally and/or vertically</li>
  <li>As of Android 4.0, app widgets have margins automatically applied</li>
</ul>

<h2>In this document</h2>

<ol>
<li><a href="#anatomy">Standard Widget Anatomy</a></li>
<li><a href="#design">Designing Widget Layouts and Background Graphics</a></li>
<li><a href="#templates">Using the App Widget Templates Pack</a></li>
</ol>

<h2>Downloads</h2>

<ol>
<li><a href="{@docRoot}shareables/app_widget_templates-v4.0.zip">App Widget Templates Pack,
  v4.0 &raquo;</a></li>
</ol>

<h2>See also</h2>

<ol>
<li><a href="{@docRoot}guide/topics/appwidgets/index.html">App Widgets</a></li>
<li>
  <a href="http://android-developers.blogspot.com/2009/04/introducing-home-screen-widgets-and.html">
    AppWidgets blog post</a></li>
</ol>

</div>
</div>


<p>App widgets (sometimes just "widgets") are a feature introduced in Android 1.5 and vastly
improved in Android 3.0 and 3.1. A widget can display an application's most timely or otherwise
relevant information at a glance, on a user's Home screen. The standard Android system image
includes several widgets, including a widget for the Analog Clock, Music, and other
applications.</p>


<img src="{@docRoot}images/widget_design/widget_examples.png"
  alt="Example app widgets in Android 4.0" id="widget_examples">

<p class="img-caption"><strong>Figure 1.</strong> Example app widgets in Android 4.0.</p>


<p>This document describes how to design a widget so that it fits graphically with other widgets and
with the other elements of the Android Home screen such as launcher icons and shortcuts. It also
describes some standards for widget artwork and some widget graphics tips and tricks.<p>

<p>For information about developing widgets, see the <a
href="{@docRoot}guide/topics/appwidgets/index.html">App Widgets</a> section of the <em>Developer's
Guide</em>.</p>


<h2 id="anatomy">Standard Widget Anatomy</h2>

<p>Typical Android app widgets have three main components: A bounding box, a frame, and the widget's
graphical controls and other elements. App widgets can contain a subset of the View widgets in
Android; supported controls include text labels, buttons, and images. For a full list of available
Views, see the <a href="{@docRoot}guide/topics/appwidgets/index.html#CreatingLayout">Creating the
App Widget Layout</a> section in the <em>Developer's Guide</em>. Well-designed widgets leave some
margins between the edges of the bounding box and the frame, and padding between the inner edges of
the frame and the widget's controls.</p>


<img src="{@docRoot}images/widget_design/widget_terms.png"
  alt="Widgets generally have margins and padding between bounding box, frame, and controls"
  id="widget_terms">

<p class="img-caption"><strong>Figure 2.</strong> Widgets generally have margins between the
bounding box and frame, and padding between the frame and widget controls.</p>


<p class="note"><strong>Note: </strong> As of Android 4.0, app widgets are automatically given
margins between the widget frame and the app widget's bounding box to provide better alignment with
other widgets and icons on the user's home screen. To take advantage of this strongly recommended
behavior, set your application's <a
href="{@docRoot}guide/topics/manifest/uses-sdk-element.html">targetSdkVersion</a> to 14 or
greater.</p>

<p>Widgets designed to fit visually with other widgets on the Home screen take cues from the other
elements on the Home screen for alignment; they also use standard shading effects. All of these
details are described in this document.</p>


<h3 id="anatomy_determining_size">Determining a size for your widget</h3>

<p>Each widget must define a <code>minWidth</code> and <code>minHeight</code>, indicating the
minimum amount of space it should consume by default. When users add a widget to their Home screen,
it will generally occupy more than the minimum width and height you specify. Android Home screens
offer users a grid of available spaces into which they can place widgets and icons. This grid can
vary by device; for example, many handsets offer a 4x4 grid, and tablets can offer a larger, 8x7
grid. <strong>When your widget is added, it will be stretched to occupy the minimum number of cells,
horizontally and vertically, required to satisfy its <code>minWidth</code> and
<code>minHeight</code> constraints.</strong> As we discuss in <a href="#design">Designing Widget
Layouts and Background Graphics</a> below, using nine-patch backgrounds and flexible layouts for app
widgets will allow your widget to gracefully adapt to the device's Home screen grid and remain
usable and aesthetically awesome.</p>

<p>While the width and height of a cell&mdash;as well as the amount of automatic margins applied to
widgets&mdash;may vary across devices, you can use the table below to roughly estimate your widget's
minimum dimensions, given the desired number of occupied grid cells:</p>

<table id="cellstable">
  <thead>
    <tr>
      <th># of Cells<br><small style="font-weight:normal">(Columns or Rows)</small></th>
      <th>Available Size (dp)<br><small style="font-weight:normal">(<code>minWidth</code> or
        <code>minHeight</code>)</small></th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>1</td>
      <td>40dp</td>
    </tr>
    <tr>
      <td>2</td>
      <td>110dp</td>
    </tr>
    <tr>
      <td>3</td>
      <td>180dp</td>
    </tr>
    <tr>
      <td>4</td>
      <td>250dp</td>
    </tr>
    <tr>
      <td>&hellip;</td>
      <td>&hellip;</td>
    </tr>
    <tr>
      <td><em>n</em></td>
      <td>70 &times; <em>n</em> &minus; 30</td>
    </tr>
  </tbody>
</table>

<p>It is a good practice to be conservative with <code>minWidth</code> and <code>minHeight</code>,
specifying the minimum size that renders the widget in a good default state. For an example of how
to provide a <code>minWidth</code> and <code>minHeight</code>, suppose you have a music player
widget that shows the currently playing song artist and title (vertically stacked), a
<strong>Play</strong> button, and a <strong>Next</strong> button:</p>


<img src="{@docRoot}images/widget_design/music_example.png"
  alt="An example music player widget" id="music_example">

<p class="img-caption"><strong>Figure 3.</strong> An example music player widget.</p>


<p>Your minimum height should be the height of your two TextViews for the artist and title, plus
some text margins. Your minimum width should be the minimum usable widths of the
<strong>Play</strong> and <strong>Next</strong> buttons, plus the minimum text width (say, the width
of 10 characters), plus any horizontal text margins.</p>


<img src="{@docRoot}images/widget_design/music_example_redline.png"
alt="Example sizes and margins for minimum width/height calculations" id="music_example_redline">

<p class="img-caption"><strong>Figure 4.</strong> Example sizes and margins for
<code>minWidth</code>/<code>minHeight</code> calculations. We chose 144dp as an example good minimum
width for the text labels.</p>


<p>Example calculations are below:</p>

<ul>
  <li><code>minWidth</code> = 144dp + (2 &times; 8dp) + (2 &times; 56dp) =
    <strong>272dp</strong></li>
  <li><code>minHeight</code> = 48dp + (2 &times; 4dp) = <strong>56dp</strong></li>
</ul>

<p>If there is any inherent content padding in your widget background nine-patch, you should add to
<code>minWidth</code> and <code>minHeight</code> accordingly.</p>


<h3 id="anatomy_resizable_widgets">Resizable widgets</h3>

<p>Widgets can be resized horizontally and/or vertically as of Android 3.1, meaning that
<code>minWidth</code> and <code>minHeight</code> effectively become the <em>default</em> size for
the widget. You can specify the minimum widget size using <code>minResizeWidth</code> and
<code>minResizeHeight</code>; these values should specify the size below which the widget would be
illegible or otherwise unusable.</p>

<p>This is generally a preferred feature for collection widgets such as those based on {@link
android.widget.ListView} or {@link android.widget.GridView}.</p>


<h3 id="anatomy_adding_margins">Adding margins to your app widget</h3>

<p>As previously mentioned, Android 4.0 will automatically add small, standard margins to each edge
of widgets on the Home screen, for applications that specify a <code>targetSdkVersion</code> of 14
or greater. This helps to visually balance the Home screen, and thus <strong>we recommend that you
do not add any extra margins outside of your app widget's background shape in Android
4.0</strong>.</p>

<p>It's easy to write a single layout that has custom margins applied for earlier versions of the
platform, and has no extra margins for Android 4.0 and greater. See <a
href="{@docRoot}guide/topics/appwidgets/index.html#AddingMargins">Adding Margins to App Widgets</a>
in the <em>Developer's Guide</em> for information on how to achieve this with layout XML.</p>


<h2 id="design">Designing Widget Layouts and Background Graphics</h2>

<p>Most widgets will have a solid background rectangle or rounded rectangle shape. It is a best
practice to define this shape using nine patches; one for each screen density (see <a
href="{@docRoot}guide/practices/screens_support.html">Supporting Multiple Screens</a> for details).
Nine-patches can be created with the <a
href="{@docRoot}guide/developing/tools/draw9patch.html">draw9patch</a> tool, or simply with a
graphics editing program such as Adobe&reg; Photoshop. This will allow the widget background shape
to take up the entire available space. The nine-patch should be edge-to-edge with no transparent
pixels providing extra margins, save for perhaps a few border pixels for <strong>subtle</strong>
drop shadows or other subtle effects.</p>

<p class="note"><strong>Note: </strong> Just like with controls in activities, you should ensure
that interactive controls have distinct visual focused and pressed states using <a
href="{@docRoot}guide/topics/resources/drawable-resource.html#StateList">state list
drawables</a>.</p>


<img src="{@docRoot}images/ninepatch_raw.png" alt="Nine-patch border pixels" id="ninepatch_raw">

<p class="img-caption"><strong>Figure 5.</strong> Nine-patch border pixels indicating stretchable
regions and content padding.</p>


<p>Some app widgets, such as those using a {@link android.widget.StackView}, have a transparent
background. For this case, each individual item in the StackView should use a nine-patch background
that is edge-to-edge with little or no border transparent pixels for margins.</p>

<p>For the contents of the widget, you should use flexible layouts such as {@link
android.widget.RelativeLayout}, {@link android.widget.LinearLayout}, or {@link
android.widget.FrameLayout}. Just as your activity layouts must adapt to different physical screen
sizes, widget layouts must adapt to different Home screen grid cell sizes.</p>

<p>Below is an example layout that a music widget showing text information and two buttons can use.
It builds upon the previous discussion of adding margins depending on OS version.</p>

<pre>
&lt;FrameLayout
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:layout_margin="@dimen/widget_margin"&gt;

  &lt;LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal"
    android:background="@drawable/my_widget_background"&gt;

    &lt;TextView
      android:id="@+id/song_info"
      android:layout_width="0dp"
      android:layout_height="match_parent"
      android:layout_weight="1" /&gt;

    &lt;Button
      android:id="@+id/play_button"
      android:layout_width="@dimen/my_button_width"
      android:layout_height="match_parent" /&gt;

    &lt;Button
      android:id="@+id/skip_button"
      android:layout_width="@dimen/my_button_width"
      android:layout_height="match_parent" /&gt;
  &lt;/LinearLayout&gt;
&lt;/FrameLayout&gt;
</pre>

<p>If you now take a look at the example music widget from the previous section, you can begin to
use flexible layouts attributes like so:</p>


<img src="{@docRoot}images/widget_design/music_example_layouts.png"
  alt="Excerpt flexible layouts and attributes for an example music widget"
  id="music_example_layouts">

<p class="img-caption"><strong>Figure 6.</strong> Excerpt flexible layouts and attributes.</p>


<p>When a user adds the widget to their home screen, on an example Android 4.0 device where each
grid cell is 80dp &times; 100dp in size and 16dp of margins are automatically applied on all sizes,
the widget will be stretched, like so:</p>


<img src="{@docRoot}images/widget_design/music_example_stretched.png"
  alt="Music widget sitting on an example 80dp x 100dp grid with 16dp of automatic margins
  added by the system" id="music_example_stretched">

<p class="img-caption"><strong>Figure 7.</strong> Music widget sitting on an example 80dp x 100dp
grid with 16dp of automatic margins added by the system.</p>


<h2 id="templates">Using the App Widget Templates Pack</h2>

<p>When starting to design a new widget, or updating an existing widget, it's a good idea to first
look at the widget design templates below. The downloadable package below includes nine-patch
background graphics, XML, and source Adobe&reg; Photoshop files for multiple screen densities, OS
version widget styles, and widget colors. The template package also contains graphics useful for
making your entire widget or parts of your widget (e.g. buttons) interactive.</p>


<img src="{@docRoot}images/widget_design/widget_template_excerpts.png"
  alt="Widget template excerpts" id="widget_template_excerpts">

<p class="img-caption"><strong>Figure 8.</strong> Excerpts from the App Widget Templates Pack
(medium-density, dark, Android 4.0/previous styles, default/focused/pressed states).</p>


<p>You can obtain the latest App Widget Templates Pack archive using the link below:</p>

<p style="margin-left:2em"><a href="{@docRoot}shareables/app_widget_templates-v4.0.zip">
  Download the App Widget Templates Pack for Android 4.0 &raquo;</a></p>