17、手势（Gesture）

 1 1,
 2 <android.gesture.GestureOverlayView
 3     android:id="@+id/gestures"
 4     android:layout_width="fill_parent" 
 5     android:layout_height="0dip"
 6     android:layout_weight="1.0" />
 7 2,
 8 GestureOverlayView gestures = (GestureOverlayView)
 9    findViewById(R.id.gestures);
10 gestures.addOnGesturePerformedListener(this);
11 
12 3,
13 public void onGesturePerformed(GestureOverlayView overlay, Gesture gesture) {
14     ArrayList<prediction> predictions = mLibrary.recognize(gesture);
15 
16     // We want at least one prediction
17     if (predictions.size() > 0) {
18         Prediction prediction = predictions.get(0);
19         // We want at least some confidence in the result
20         if (prediction.score > 1.0) {
21             // Show the spell
22             Toast.makeText(this, prediction.name, Toast.LENGTH_SHORT).show();
23         }
24     }
25 }

 1 And here is what the XML layout looks like:
 2 
 3 <android.gesture.GestureOverlayView
 4     xmlns:android="http://schemas.android.com/apk/res/android"
 5     android:id="@+id/gestures"
 6     android:layout_width="fill_parent"
 7     android:layout_height="fill_parent"
 8     
 9     android:gestureStrokeType="multiple"
10     android:eventsInterceptionEnabled="true"
11     android:orientation="vertical">
12 
13     <ListView
14         android:id="@android:id/list"  
15         android:layout_width="fill_parent" 
16         android:layout_height="fill_parent"  />
17 
18 </android.gesture.GestureOverlayView>
19 In this application, the gestures view is an overlay on top of a regular ListView. The overlay also specifies a few properties that we did not need before:
20 
21 gestureStrokeType: indicates whether we want to recognize gestures made of a single stroke or multiple strokes. Since one of our gestures is the "+" symbol, we need multiple strokes
22 eventsInterceptionEnabled: when set to true, this property tells the overlay to steal the events from its children as soon as it knows the user is really drawing a gesture. This is useful when there‘s a scrollable view under the overlay, to avoid scrolling the underlying child as the user draws his gesture
23 orientation: indicates the scroll orientation of the views underneath. In this case the list scrolls vertically, which means that any horizontal gestures (like action_delete) can immediately be recognized as a gesture. Gestures that start with a vertical stroke must contain at least one horizontal component to be recognized. In other words, a simple vertical line cannot be recognized as a gesture since it would conflict with the list‘s scrolling.
24 The code used to load and set up the gestures library and overlay is exactly the same as before. The only difference is that we now check the name of the predictions to know what the user intended to do:
25 
26 public void onGesturePerformed(GestureOverlayView overlay, Gesture gesture) {
27     ArrayList<Prediction> predictions = mLibrary.recognize(gesture);
28     if (predictions.size() > 0 && predictions.get(0).score > 1.0) {
29         String action = predictions.get(0).name;
30         if ("action_add".equals(action)) {
31             Toast.makeText(this, "Adding a contact", Toast.LENGTH_SHORT).show();
32         } else if ("action_delete".equals(action)) {
33 Toast.makeText(this, "Removing a contact",
34    Toast.LENGTH_SHORT).show();
35         } else if ("action_refresh".equals(action)) {
36 Toast.makeText(this, "Reloading contacts",
37  Toast.LENGTH_SHORT).show();
38         }
39     }
40 }