1page.title=Addressing Common Issues
2
3@jd:body
4
5<div id="tb-wrapper">
6<div id="tb">
7<h2>This lesson teaches you to</h2>
8<ol>
9  <li><a href="#ScreenShape">Detect the Shape of the Screen</a></li>
10  <li><a href="#PeekCards">Accomodate Peek Cards</a></li>
11  <li><a href="#RelativeMeasurements">Use Relative Measurements</a></li>
12</ol>
13<h2>You should also read</h2>
14<ul>
15  <li><a href="{@docRoot}design/wear/watchfaces.html">Watch Faces for Android Wear</a></li>
16</ul>
17</div>
18</div>
19
20<p>Creating a custom watch face for Android Wear is substantially different from creating
21notifications and wearable-specific activities. This class shows you how to resolve some
22issues that you may encounter as you implement your first few watch faces.</p>
23
24
25
26<h2 id="ScreenShape">Detect the Shape of the Screen</h2>
27
28<p>Some Android Wear devices have square screens, while others have round screens. Devices with
29round screens can contain an inset (or "chin") at the bottom of the screen. Your watch face
30should adapt to and take advantage of the particular shape of the screen, as described in the
31<a href="{@docRoot}design/wear/watchfaces.html">design guidelines</a>.</p>
32
33<p>Android Wear lets your watch face determine the screen shape at runtime. To detect whether
34the screen is square or round, override the
35<a href="{@docRoot}reference/android/service/wallpaper/WallpaperService.Engine.html#onApplyWindowInsets(android.view.WindowInsets)"><code>onApplyWindowInsets()</code></a>
36method in the
37<a href="{@docRoot}reference/android/support/wearable/watchface/CanvasWatchFaceService.Engine.html"><code>CanvasWatchFaceService.Engine</code></a>
38class as follows:</p>
39
40<pre>
41private class Engine extends CanvasWatchFaceService.Engine {
42    boolean mIsRound;
43    int mChinSize;
44
45    &#64;Override
46    public void onApplyWindowInsets(WindowInsets insets) {
47        super.onApplyWindowInsets(insets);
48        mIsRound = insets.isRound();
49        mChinSize = insets.getSystemWindowInsetBottom();
50    }
51    ...
52}
53</pre>
54
55<p>To adapt your design when you draw your watch face, check the value of the
56<code>mIsRound</code> and <code>mChinSize</code> member variables.</p>
57
58
59
60<h2 id="PeekCards">Accomodate Peek Cards</h2>
61
62<div style="float:right;margin-left:30px;width:340px">
63<img src="{@docRoot}training/wearables/watch-faces/images/AnalogNoCard.png" alt=""
64     width="160" height="145" style="margin-right:7px"/>
65<img src="{@docRoot}training/wearables/watch-faces/images/AnalogWithCard.png" alt=""
66     width="160" height="145"/>
67<p class="img-caption"><strong>Figure 1.</strong> Some analog watch faces require adjustments
68when notification cards appear.</p>
69</div>
70
71<p>When users receive a notification, the notification card may cover a significant portion of the
72screen, depending on the
73<a href="{@docRoot}training/wearables/watch-faces/drawing.html#SystemUI">system UI style</a>. Your
74watch face should adapt to these situations by ensuring that users can still tell the time while
75the notification card is present.</p>
76
77<p>Analog watch faces can make adjustments when a notification card is present, like scaling
78down the watch face to fit inside the portion of the screen not covered by the peek card. Digital
79watch faces that display the time in the area of the screen not covered by peek cards do not
80usually require adjustments. To determine the free space above the peek card so you can adapt
81your watch face, use the
82<a href="{@docRoot}reference/android/support/wearable/watchface/WatchFaceService.Engine.html#getPeekCardPosition()"><code>WatchFaceService.Engine.getPeekCardPosition()</code></a>
83method.</p>
84
85<p>In ambient mode, peek cards have a transparent background. If your watch face contains details
86near the card in ambient mode, consider drawing a black rectangle over them to ensure that users
87can read the contents of the card.</p>
88
89
90
91<h2 id="SystemIndicators">Configure the System Indicators</h2>
92
93<div style="width:200px;float:right;margin-left:10px">
94<img src="{@docRoot}training/wearables/watch-faces/images/Indicators_Cropped.png" alt=""
95     width="200" height="195"/>
96<p class="img-caption" style="margin-left:25px;margin-top:-25px">
97<strong>Figure 2.</strong> The status bar.</p>
98</div>
99
100<p>To ensure that the system indicators remain visible, you can configure their position on the
101screen and whether they need background protection when you create a
102<a href="{@docRoot}reference/android/support/wearable/watchface/WatchFaceStyle.html"><code>WatchFaceStyle</code></a>
103instance:</p>
104
105<ul>
106<li>To set the position of the status bar, use the
107<a href="{@docRoot}reference/android/support/wearable/watchface/WatchFaceStyle.Builder.html#setStatusBarGravity(int)"><code>setStatusBarGravity()</code></a>
108method.</li>
109<li>To set the position of the hotword, use the
110<a href="{@docRoot}reference/android/support/wearable/watchface/WatchFaceStyle.Builder.html#setHotwordIndicatorGravity(int)"><code>setHotwordIndicatorGravity()</code></a>
111method.</li>
112<li>To protect the status bar and hotword with a semi-transparent gray background, use the
113<a href="{@docRoot}reference/android/support/wearable/watchface/WatchFaceStyle.Builder.html#setViewProtection(int)"><code>setViewProtection()</code></a>
114method. This is usually necessary if your watch face has a light background, since the system
115indicators are white.</li>
116</ul>
117
118<p>For more information about the system indicators, see <a
119href="{@docRoot}training/wearables/watch-faces/drawing.html#SystemUI">Configure the System UI</a>
120and read the <a href="{@docRoot}design/wear/watchfaces.html">design guidelines</a>.</p>
121
122
123
124<h2 id="RelativeMeasurements">Use Relative Measurements</h2>
125
126<p>Android Wear devices from different manufacturers feature screens with a variety of sizes and
127resolutions. Your watch face should adapt to these variations by using relative measurements
128instead of absolute pixel values.</p>
129
130<p>When you draw your watch face, obtain the size of the canvas with the {@link
131android.graphics.Canvas#getWidth Canvas.getWidth()} and {@link
132android.graphics.Canvas#getHeight Canvas.getHeight()} methods and set the positions of your
133graphic elements using values that are some fraction of the detected screen size. If you resize
134the elements of your watch face in response to a peek card, use values that are some fraction
135of the remaining space above the card to redraw your watch face.</p>
136