android_frameworks_base/docs/html/training/wearables/watch-faces/issues.jd

page.title=Addressing Common Issues

@jd:body

<div id="tb-wrapper">
<div id="tb">
<h2>This lesson teaches you to</h2>
<ol>
  <li><a href="#ScreenShape">Detect the Shape of the Screen</a></li>
  <li><a href="#PeekCards">Accomodate Peek Cards</a></li>
  <li><a href="#RelativeMeasurements">Use Relative Measurements</a></li>
</ol>
<h2>You should also read</h2>
<ul>
  <li><a href="{@docRoot}design/wear/watchfaces.html">Watch Faces for Android Wear</a></li>
</ul>
</div>
</div>

<p>Creating a custom watch face for Android Wear is substantially different from creating
notifications and wearable-specific activities. This class shows you how to resolve some
issues that you may encounter as you implement your first few watch faces.</p>



<h2 id="ScreenShape">Detect the Shape of the Screen</h2>

<p>Some Android Wear devices have square screens, while others have round screens. Devices with
round screens can contain an inset (or "chin") at the bottom of the screen. Your watch face
should adapt to and take advantage of the particular shape of the screen, as described in the
<a href="{@docRoot}design/wear/watchfaces.html">design guidelines</a>.</p>

<p>Android Wear lets your watch face determine the screen shape at runtime. To detect whether
the screen is square or round, override the <code>onApplyWindowInsets()</code> method in the
<code>CanvasWatchFaceService.Engine</code> class as follows:</p>

<pre>
private class Engine extends CanvasWatchFaceService.Engine {
    boolean mIsRound;
    int mChinSize;

    &#64;Override
    public void onApplyWindowInsets(WindowInsets insets) {
        super.onApplyWindowInsets(insets);
        mIsRound = insets.isRound();
        mChinSize = insets.getSystemWindowInsetBottom();
    }
    ...
}
</pre>

<p>To adapt your design when you draw your watch face, check the value of the
<code>mIsRound</code> and <code>mChinSize</code> member variables.</p>



<h2 id="PeekCards">Accomodate Peek Cards</h2>

<div style="float:right;margin-left:30px;width:340px">
<img src="{@docRoot}training/wearables/watch-faces/images/AnalogNoCard.png" alt=""
     width="160" height="145" style="margin-right:7px"/>
<img src="{@docRoot}training/wearables/watch-faces/images/AnalogWithCard.png" alt=""
     width="160" height="145"/>
<p class="img-caption"><strong>Figure 1.</strong> Some analog watch faces require adjustments
when notification cards appear.</p>
</div>

<p>When users receive a notification, the notification card may cover a significant portion of the
screen, depending on the
<a href="{@docRoot}training/wearables/watch-faces/drawing.html#SystemUI">system UI style</a>. Your
watch face should adapt to these situations by ensuring that users can still tell the time while
the notification card is present.</p>

<p>Analog watch faces can make adjustments when a notification card is present, like scaling
down the watch face to fit inside the portion of the screen not covered by the peek card. Digital
watch faces that display the time in the area of the screen not covered by peek cards do not
usually require adjustments. To determine the free space above the peek card so you can adapt
your watch face, use the <code>WatchFaceService.getPeekCardPosition()</code> method.</p>

<p>In ambient mode, peek cards have a transparent background. If your watch face contains details
near the card in ambient mode, consider drawing a black rectangle over them to ensure that users
can read the contents of the card.</p>



<h2 id="SystemIndicators">Configure the System Indicators</h2>

<div style="width:200px;float:right;margin-left:10px">
<img src="{@docRoot}training/wearables/watch-faces/images/Indicators_Cropped.png" alt=""
     width="200" height="195"/>
<p class="img-caption" style="margin-left:25px;margin-top:-25px">
<strong>Figure 2.</strong> The status bar.</p>
</div>

<p>To ensure that the system indicators remain visible, you can configure their position on the
screen and whether they need background protection when you create a <code>WatchFaceStyle</code>
instance:</p>

<ul>
<li>To set the position of the status bar, use the <code>setStatusBarGravity()</code> method.</li>
<li>To set the position of the hotword, use the <code>setHotwordIndicatorGravity()</code>
method.</li>
<li>To protect the status bar and hotword with a semi-transparent gray background, use the
<code>setViewProtection()</code> method. This is usually necessary if your watch face has a
light background, since the system indicators are white.</li>
</ul>

<p>For more information about the system indicators, see <a
href="{@docRoot}training/wearables/watch-faces/drawing.html#SystemUI">Configure the System UI</a>
and read the <a href="{@docRoot}design/wear/watchfaces.html">design guidelines</a>.</p>



<h2 id="RelativeMeasurements">Use Relative Measurements</h2>

<p>Android Wear devices from different manufacturers feature screens with a variety of sizes and
resolutions. Your watch face should adapt to these variations by using relative measurements
instead of absolute pixel values.</p>

<p>When you draw your watch face, obtain the size of the canvas with the {@link
android.graphics.Canvas#getWidth Canvas.getWidth()} and {@link
android.graphics.Canvas#getHeight Canvas.getHeight()} methods and set the positions of your
graphic elements using values that are some fraction of the detected screen size. If you resize
the elements of your watch face in response to a peek card, use values that are some fraction
of the remaining space above the card to redraw your watch face.</p>