Update camera continuous autofocus javadoc.

Suppose applications call autoFocus in CAF picture mode. If
CAF is in the middle of scanning, the picture is very likely to
be blurry. Change focus callback to return when the scanning
finishes.

bug:5514415
Change-Id: Ibcb8f92a5263d7dbd7cce54df3617fb21c6255d4

Author: Wu-cheng Li

core/java/android/hardware/Camera.java

@@ -1687,15 +1687,18 @@ public class Parameters {
          * aggressive than {@link #FOCUS_MODE_CONTINUOUS_VIDEO}. Auto focus
          * starts when the parameter is set.
          *
-         * <p>If applications call {@link #autoFocus(AutoFocusCallback)} in this
-         * mode, the focus callback will immediately return with a boolean that
-         * indicates whether the focus is sharp or not. The apps can then decide
-         * if they want to take a picture immediately or to change the focus
-         * mode to auto, and run a full autofocus cycle. The focus position is
-         * locked after autoFocus call. If applications want to resume the
-         * continuous focus, cancelAutoFocus must be called. Restarting the
-         * preview will not resume the continuous autofocus. To stop continuous
-         * focus, applications should change the focus mode to other modes.
+         * <p>Applications can call {@link #autoFocus(AutoFocusCallback)} in
+         * this mode. If the autofocus is in the middle of scanning, the focus
+         * callback will return when it completes. If the autofocus is not
+         * scanning, the focus callback will immediately return with a boolean
+         * that indicates whether the focus is sharp or not. The apps can then
+         * decide if they want to take a picture immediately or to change the
+         * focus mode to auto, and run a full autofocus cycle. The focus
+         * position is locked after autoFocus call. If applications want to
+         * resume the continuous focus, cancelAutoFocus must be called.
+         * Restarting the preview will not resume the continuous autofocus. To
+         * stop continuous focus, applications should change the focus mode to
+         * other modes.
          *
          * @see #FOCUS_MODE_CONTINUOUS_VIDEO
          */

include/camera/CameraParameters.h

@@ -644,15 +644,17 @@ class CameraParameters
     // than FOCUS_MODE_CONTINUOUS_VIDEO. Auto focus starts when the parameter is
     // set.
     //
-    // If applications call CameraHardwareInterface.autoFocus in this mode, the
-    // focus callback will immediately return with a boolean that indicates
-    // whether the focus is sharp or not. The apps can then decide if they want
-    // to take a picture immediately or to change the focus mode to auto, and
-    // run a full autofocus cycle. The focus position is locked after autoFocus
-    // call. If applications want to resume the continuous focus,
-    // cancelAutoFocus must be called. Restarting the preview will not resume
-    // the continuous autofocus. To stop continuous focus, applications should
-    // change the focus mode to other modes.
+    // Applications can call CameraHardwareInterface.autoFocus in this mode. If
+    // the autofocus is in the middle of scanning, the focus callback will
+    // return when it completes. If the autofocus is not scanning, focus
+    // callback will immediately return with a boolean that indicates whether
+    // the focus is sharp or not. The apps can then decide if they want to take
+    // a picture immediately or to change the focus mode to auto, and run a full
+    // autofocus cycle. The focus position is locked after autoFocus call. If
+    // applications want to resume the continuous focus, cancelAutoFocus must be
+    // called. Restarting the preview will not resume the continuous autofocus.
+    // To stop continuous focus, applications should change the focus mode to
+    // other modes.
     static const char FOCUS_MODE_CONTINUOUS_PICTURE[];
 
 private: