Always enable hardware layers in widgets in keyguard while dragging.

This fixes a performance issue on the 7" tablet where disabling hardware
layers in landscape mode resulted in extremely bad drawing performance.

The code now enables hardware layers for all the widgets while the user
is dragging.

Fixes bug 7274971

Change-Id: Iafd18fb317fcd3caad45791fe5a0f111d40a1ed4

Author: Jim Miller

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

@@ -117,14 +117,7 @@ void setOverScrollAmount(float r, boolean left) {
             mOverScrollAmount = r;
             mForegroundGradient = left ? mLeftToRightGradient : mRightToLeftGradient;
             mForegroundAlpha = (int) Math.round((0.85f * r * 255));
-            if (getLayerType() != LAYER_TYPE_HARDWARE) {
-                setLayerType(LAYER_TYPE_HARDWARE, null);
-            }
             invalidate();
-        } else {
-            if (getLayerType() != LAYER_TYPE_NONE) {
-                setLayerType(LAYER_TYPE_NONE, null);
-            }
         }
     }
 }

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

@@ -76,6 +76,25 @@ protected void onUnhandledTap(MotionEvent ev) {
         }
     }
 
+    @Override
+    protected void onPageBeginMoving() {
+        // Enable hardware layers while pages are moving
+        // TODO: We should only do this for the two views that are actually moving
+        int children = getChildCount();
+        for (int i = 0; i < children; i++) {
+            getChildAt(i).setLayerType(LAYER_TYPE_HARDWARE, null);
+        }
+    }
+
+    @Override
+    protected void onPageEndMoving() {
+        // Disable hardware layers while pages are moving
+        int children = getChildCount();
+        for (int i = 0; i < children; i++) {
+            getChildAt(i).setLayerType(LAYER_TYPE_NONE, null);
+        }
+    }
+
     /*
      * This interpolator emulates the rate at which the perceived scale of an object changes
      * as its distance from a camera increases. When this interpolator is applied to a scale