Make partially visible widget pages not important for accessibility.

1. If the lockscreen has more than one widet, the left and right widget
   pages are partially on the screen and visible. Therefore they may
   take accessibility focus so the user will hear a prompt that he is
   on the partially visible widget page but will not be able to interact
   with it - confusing. This change makes partially shown windget frames
   not important for accessibility.

bug:7454355

Change-Id: I475b21e215474a4421acaec485cde64dc4e2aee5

Author: sganov

policy/src/com/android/internal/policy/impl/keyguard/KeyguardWidgetPager.java

@@ -167,6 +167,22 @@ public void sendAccessibilityEvent(int eventType) {
         }
     }
 
+    private void updateWidgetFramesImportantForAccessibility() {
+        final int pageCount = getPageCount();
+        for (int i = 0; i < pageCount; i++) {
+            KeyguardWidgetFrame frame = getWidgetPageAt(i);
+            updateWidgetFrameImportantForAccessibility(frame);
+        }
+    }
+
+    private void updateWidgetFrameImportantForAccessibility(KeyguardWidgetFrame frame) {
+        if (frame.getContentAlpha() <= 0) {
+            frame.setImportantForAccessibility(View.IMPORTANT_FOR_ACCESSIBILITY_NO);
+        } else {
+            frame.setImportantForAccessibility(View.IMPORTANT_FOR_ACCESSIBILITY_YES);
+        }
+    }
+
     private void userActivity() {
         if (mCallbacks != null) {
             mCallbacks.onUserActivityTimeoutChanged();
@@ -276,6 +292,7 @@ public void addWidget(View widget, int pageIndex) {
                 content.getContentDescription());
             frame.setContentDescription(contentDescription);
         }
+        updateWidgetFrameImportantForAccessibility(frame);
     }
 
     /**
@@ -512,6 +529,12 @@ public void showInitialPageHints() {
         }
     }
 
+    @Override
+    void setCurrentPage(int currentPage) {
+        super.setCurrentPage(currentPage);
+        updateWidgetFramesImportantForAccessibility();
+    }
+
     @Override
     public void onAttachedToWindow() {
         super.onAttachedToWindow();
@@ -618,6 +641,7 @@ public void onAnimationEnd(Animator animation) {
                 if (!show) {
                     disablePageLayers();
                 }
+                updateWidgetFramesImportantForAccessibility();
             }
         });
         mChildrenOutlineFadeAnimation.start();