docs/html/wear/preview/features/gestures.jd

page.title=Wrist Gestures
meta.keywords="wear-preview"
page.tags="wear-preview"
page.image=images/cards/card-n-sdk_2x.png

@jd:body

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

<h2>In this document</h2>

  <ul>
    <li><a href="#using_wlv">Using a WearableListView</a></li>
    <li><a href="#using_key_events">Using Key Events Directly</a></li>
    <li><a href="#best_practices">Best Practices</a></li>
  </ul>

</div>
</div>

    <p>
      Wrist gestures can enable quick, one-handed interactions with your app
      when use of a touch screen is inconvenient. For example, a user can scroll
      through notifications with one hand while holding a cup of water with the
      other. Other examples of using wrist gestures when a touch screen would
      be inconvenient include:
    </p>

    <ul>
      <li>In an app for jogging, navigating through vertical screens that show
      the steps taken, time elapsed, and current pace
      </li>

      <li>At the airport with luggage, scrolling through flight and gate
      information
      </li>

      <li>Scrolling through news articles
      </li>
    </ul>

    <p>
      To review the wrist gestures on your watch, first confirm gestures are
      turned on by selecting <strong>Settings &gt; Gestures &gt; Wrist Gestures
      On</strong>. (Wrist gestures are on by default.) Then complete the
      Gestures tutorial on the watch (<strong>Settings &gt; Gestures &gt;
      Launch Tutorial</strong>).
    </p>

    <p>
      The following gestures from the <a href=
      "https://support.google.com/androidwear/answer/6312406">Android Wear
      Help</a> are unavailable to apps:
    </p>

    <ul>
      <li>Push wrist down
      </li>

      <li>Raise wrist up
      </li>

      <li>Shaking the wrist
      </li>
    </ul>

    <p>
      Wrist gestures can be used in these ways:
    </p>

    <ul>
      <li>
        <a href="#using_wlv">Using a WearableListView</a>, which
        has predefined gesture actions
      </li>

      <li>
        <a href="#using_key_events">Using key events directly</a> to
        define new user actions
      </li>
    </ul>

    <p>
      Each wrist gesture is mapped to an <code>int</code> constant from the
      <code><a href=
      "{@docRoot}reference/android/view/KeyEvent.html">KeyEvent</a></code>
      class, as shown in the following table:
    </p>

    <table>
      <tr>
        <th>
          Gesture
        </th>
        <th>
          KeyEvent
        </th>
        <th>
          Description
        </th>
      </tr>

      <tr>
        <td>
          Flick wrist out
        </td>
        <td>
          <a href=
          "{@docRoot}reference/android/view/KeyEvent.html#KEYCODE_NAVIGATE_NEXT">
          KEYCODE_NAVIGATE_NEXT</a>
        </td>
        <td>
          This key code goes to the next item.
        </td>
      </tr>

      <tr>
        <td>
          Flick wrist in
        </td>
        <td>
          <a href=
          "{@docRoot}reference/android/view/KeyEvent.html#KEYCODE_NAVIGATE_PREVIOUS">
          KEYCODE_NAVIGATE_PREVIOUS</a>
        </td>
        <td>
          This key code goes to the previous item.
        </td>
      </tr>
    </table>

    <h2 id="using_wlv">
      Using a WearableListView
    </h2>

    <p>
      A <code><a href=
      "{@docRoot}reference/android/support/wearable/view/WearableListView.html">
      WearableListView</a></code> has predefined actions for occurrences of
      wrist gestures when the View has the focus. For more information, see
      <a href="#best_practices">Best Practices</a>. For information about using
      <code>WearableListView</code>, see <a href=
      "{@docRoot}training/wearables/ui/lists.html">Creating
      Lists</a>.
    </p>

    <p>
      Even if you use a <code>WearableListView</code>, you may want to use
      constants from the <code><a href=
      "{@docRoot}reference/android/view/KeyEvent.html">KeyEvent</a></code>
      class. The predefined actions can be overridden by subclassing the
      <code>WearableListView</code> and re-implementing the
      <code>onKeyDown()</code> callback. The behavior can be disabled entirely
      by using <code>setEnableGestureNavigation(false)</code>. Also see
      <a href="{@docRoot}training/keyboard-input/commands.html">
      Handling Keyboard Actions</a>.
    </p>

    <h2 id="using_key_events">
      Using Key Events Directly
    </h2>

    <p>
      You can use key events outside of a <code><a href=
      "{@docRoot}reference/android/support/wearable/view/WearableListView.html">
      WearableListView</a></code> to trigger new actions in response to gesture
      events. Importantly, these gesture events:
    </p>

    <ul>
      <li>Are recognized when a device is in Active mode
      </li>

      <li>Are delivered in the same way as all key events
      </li>
    </ul>

    <p>
      Specifically, these events are delivered to the top Activity, to the View
      with keyboard focus. Just as any other key event, a class that relates to
      user interaction (such as a View or an Activity) that implements
      <code><a href=
      "{@docRoot}reference/android/view/KeyEvent.Callback.html">
      KeyEvent.Callback</a></code> can listen to key events that relate to
      wrist gestures. The Android framework calls the View or Activity that has
      the focus with the key events; for gestures, the <code>onKeyDown()</code>
      method callback is called when gestures occur.
    </p>

    <p>
      As an example, an app may override predefined actions in a View or
      Activity (both implementing <code>KeyEvent.Callback</code>) as follows:
    </p>

    <pre>
public final class GesturesActivity extends Activity {

 &#64;Override /* KeyEvent.Callback */
 public boolean onKeyDown(int keyCode, KeyEvent event) {
  switch (keyCode) {
   case KeyEvent.KEYCODE_NAVIGATE_NEXT:
    // Do something that advances a user View to the next item in an ordered list.
    return moveToNextItem();
   case KeyEvent.KEYCODE_NAVIGATE_PREVIOUS:
    // Do something that advances a user View to the previous item in an ordered list.
    return moveToPreviousItem();
  }
  // If you did not handle it, let it be handled by the next possible element as deemed by the Activity.
  return super.onKeyDown(keyCode, event);
 }

 /** Shows the next item in the custom list. */
 private boolean moveToNextItem() {
  boolean handled = false;
  …
  // Return true if handled successfully, otherwise return false.
  return handled;
 }

 /** Shows the previous item in the custom list. */
 private boolean moveToPreviousItem() {
  boolean handled = false;
  …
  // Return true if handled successfully, otherwise return false.
  return handled;
 }
}
</pre>

    <h2 id="best_practices">
      Best Practices
    </h2>

    <ul>
      <li>Review the <code><a href=
      "{@docRoot}reference/android/view/KeyEvent.html">KeyEvent</a></code>
      and <code><a href=
      "{@docRoot}reference/android/view/KeyEvent.Callback.html">
        KeyEvent.Callback</a></code> pages for the delivery of key events to
        your View and Activity.
      </li>

      <li>Keep a consistent directional affordance:
        <ul>
          <li>Use "Flick wrist out" for next, "Flick wrist in" for previous
          </li>
        </ul>
      </li>

      <li>Have a touch parallel for a gesture.
      </li>

      <li>Provide visual feedback.
      </li>

      <li>Don't use a keycode to implement functionality that would be
      counter-intuitive to the rest of the system. For example, do not use
      <code>KEYCODE_NAVIGATE_NEXT</code> to cancel an action or to navigate the
      left-right axis with flicks.
      </li>

      <li>Don't intercept the key events on elements that are not part of the
      user interface, for example the Views that are offscreen or partially
      covered. This is the same as any other key event.
      </li>

      <li>Don't reinterpret repeated flick gestures into your own, new gesture.
      It may conflict with the system's "Shaking the wrist" gesture.
      </li>

      <li>For a View to receive gesture key events, it must have <a href=
      "{@docRoot}reference/android/view/View.html#attr_android:focusable">
        focus</a>; see <a href=
        "{@docRoot}reference/android/view/View.html#setFocusable(boolean)">
        View::setFocusable()</a>. Because gestures are treated as key events,
        they trigger a transition out of "Touch mode" that may do unexpected
        things. Therefore, since users may alternate between using touch and
        gestures, the <a href=
        "{@docRoot}reference/android/view/View.html#setFocusableInTouchMode(boolean)">
        View::setFocusableInTouchmode()</a> method may be necessary. In some
        cases, it also may be necessary to use
        <code>setDescendantFocusability(FOCUS_BEFORE_DESCENDANTS)</code> so
        that when focus changes after a change to or from "Touch mode," your
        intended View gets the focus.
      </li>

      <li>Use <code>requestFocus()</code> and <code>clearFocus()</code>
      carefully:
        <ul>
          <li>When calling <code><a href=
          "{@docRoot}reference/android/view/View.html#requestFocus()">
            requestFocus()</a></code>, be sure that the View really should have
            focus. If the View is offscreen, or is covered by another View,
            surprises can occur when gestures trigger callbacks.
          </li>

          <li>The <code><a href=
          "{@docRoot}reference/android/view/View.html#clearFocus()">
            clearFocus()</a></code> initiates a focus search to find another
            suitable View. Depending on the View hierarchy, this search might
            require non-trivial computation. It can also end up assigning focus
            to a View you don’t expect to receive focus.
          </li>
        </ul>
      </li>

      <li>Key events are delivered first to the View with focus in the View
      hierarchy. If the focused View does not handle the event (i.e., returns
      <code>false</code>), the event is not delivered to the parent View, even
      if it can receive focus and has a <a href=
      "{@docRoot}reference/android/text/method/KeyListener.html">
        KeyListener</a>. Rather, the event is delivered to the current Activity
        holding the View hierarchy with focus. Thus, it may be necessary to
        catch all events at the higher level and then pass relevant codes down.
        Alternatively, you might subclass the Activity and override the
        <code><a href=
        "{@docRoot}reference/android/app/Activity.html#dispatchKeyEvent(android.view.KeyEvent)">
        dispatchKeyEvent(KeyEvent event)</a></code> method to ensure that keys
        are intercepted when necessary, or are handled when not handled at
        lower layers.
      </li>
    </ul>