1 files changed, 69 insertions, 0 deletions
diff --git a/src/com/android/launcher3/allapps/search/HeaderElevationController.java b/src/com/android/launcher3/allapps/search/HeaderElevationController.java
new file mode 100644
index 000000000..ab4e88fc8
--- /dev/null
+++ b/src/com/android/launcher3/allapps/search/HeaderElevationController.java
@@ -0,0 +1,69 @@
+package com.android.launcher3.allapps.search;
+
+import android.content.res.Resources;
+import android.graphics.Outline;
+import android.support.v7.widget.RecyclerView;
+import android.view.View;
+import android.view.ViewOutlineProvider;
+
+import com.android.launcher3.BaseRecyclerView;
+import com.android.launcher3.R;
+import com.android.launcher3.Utilities;
+
+/**
+ * Helper class for controlling the header elevation in response to RecyclerView scroll.
+ */
+public class HeaderElevationController extends RecyclerView.OnScrollListener {
+
+    private final View mHeader;
+    private final float mMaxElevation;
+    private final float mScrollToElevation;
+
+    private int mCurrentY = 0;
+
+    public HeaderElevationController(View header) {
+        mHeader = header;
+        final Resources res = mHeader.getContext().getResources();
+        mMaxElevation = res.getDimension(R.dimen.all_apps_header_max_elevation);
+        mScrollToElevation = res.getDimension(R.dimen.all_apps_header_scroll_to_elevation);
+
+        // We need to provide a custom outline so the shadow only appears on the bottom edge.
+        // The top, left and right edges are all extended out, and the shadow is clipped
+        // by the parent.
+        final ViewOutlineProvider vop = new ViewOutlineProvider() {
+            @Override
+            public void getOutline(View view, Outline outline) {
+                final View parent = (View) mHeader.getParent();
+
+                final int left = parent.getLeft(); // Use the parent to account for offsets
+                final int top = view.getTop();
+                final int right = left + view.getWidth();
+                final int bottom = view.getBottom();
+
+                final int offset = Utilities.pxFromDp(mMaxElevation, res.getDisplayMetrics());
+                outline.setRect(left - offset, top - offset, right + offset, bottom);
+            }
+        };
+        mHeader.setOutlineProvider(vop);
+    }
+
+    public void reset() {
+        mCurrentY = 0;
+        onScroll(mCurrentY);
+    }
+
+    @Override
+    public final void onScrolled(RecyclerView recyclerView, int dx, int dy) {
+        mCurrentY = ((BaseRecyclerView) recyclerView).getCurrentScrollY();
+        onScroll(mCurrentY);
+    }
+
+    private void onScroll(int scrollY) {
+        float elevationPct = Math.min(scrollY, mScrollToElevation) / mScrollToElevation;
+        float newElevation = mMaxElevation * elevationPct;
+        if (Float.compare(mHeader.getElevation(), newElevation) != 0) {
+            mHeader.setElevation(newElevation);
+        }
+    }
+
+}