Cancel band selection on directory change.

This is a workaround for N. Ideally we should keep the band selection,
as directory may change very often, eg. during loading, or downloading
a file (every second).

Bug: 27224277
Change-Id: I40cfb12c4f7928c4e0d6e675e91ba30ab3a6ab52

packages/DocumentsUI/src/com/android/documentsui/dirlist/MultiSelectManager.java

@@ -154,6 +154,10 @@ public final class MultiSelectManager {
                         // Update the selection to remove any disappeared IDs.
                         mSelection.cancelProvisionalSelection();
                         mSelection.intersect(mModelIds);
+
+                        if (mBandManager != null && mBandManager.isActive()) {
+                            mBandManager.endBandSelect();
+                        }
                     }
 
                     @Override
@@ -940,6 +944,10 @@ public final class MultiSelectManager {
          * Layout items are excluded from the GridModel.
          */
         boolean isLayoutItem(int adapterPosition);
+        /**
+         * Items may be in the adapter, but without an attached view.
+         */
+        boolean hasView(int adapterPosition);
     }
 
     /** Recycler view facade implementation backed by good ol' RecyclerView. */
@@ -1061,6 +1069,11 @@ public final class MultiSelectManager {
                     return true;
             }
         }
+
+        @Override
+        public boolean hasView(int pos) {
+            return mView.findViewHolderForAdapterPosition(pos) != null;
+        }
     }
 
     public interface Callback {
@@ -1473,10 +1486,14 @@ public final class MultiSelectManager {
          *     y-value.
          */
         void startSelection(Point relativeOrigin) {
+            recordVisibleChildren();
+            if (isEmpty()) {
+                // The selection band logic works only if there is at least one visible child.
+                return;
+            }
+
             mIsActive = true;
             mPointer = mHelper.createAbsolutePoint(relativeOrigin);
-
-            recordVisibleChildren();
             mRelativeOrigin = new RelativePoint(mPointer);
             mRelativePointer = new RelativePoint(mPointer);
             computeCurrentSelection();
@@ -1530,7 +1547,11 @@ public final class MultiSelectManager {
         private void recordVisibleChildren() {
             for (int i = 0; i < mHelper.getVisibleChildCount(); i++) {
                 int adapterPosition = mHelper.getAdapterPositionAt(i);
-                if (!mHelper.isLayoutItem(adapterPosition) &&
+                // Sometimes the view is not attached, as we notify the multi selection manager
+                // synchronously, while views are attached asynchronously. As a result items which
+                // are in the adapter may not actually have a corresponding view (yet).
+                if (mHelper.hasView(adapterPosition) &&
+                        !mHelper.isLayoutItem(adapterPosition) &&
                         !mKnownPositions.get(adapterPosition)) {
                     mKnownPositions.put(adapterPosition, true);
                     recordItemData(mHelper.getAbsoluteRectForChildViewAt(i), adapterPosition);
@@ -1538,6 +1559,13 @@ public final class MultiSelectManager {
             }
         }
 
+        /**
+         * Checks if there are any recorded children.
+         */
+        private boolean isEmpty() {
+            return mColumnBounds.size() == 0 || mRowBounds.size() == 0;
+        }
+
         /**
          * Updates the limits lists and column map with the given item metadata.
          * @param absoluteChildRect The absolute rectangle for the child view being processed.

packages/DocumentsUI/tests/src/com/android/documentsui/dirlist/MultiSelectManager_GridModelTest.java

@@ -448,6 +448,11 @@ public class MultiSelectManager_GridModelTest extends AndroidTestCase {
             return false;
         }
 
+        @Override
+        public boolean hasView(int adapterPosition) {
+            return true;
+        }
+
         public static final class Item {
             public String name;
             public Rect rect;

packages/DocumentsUI/tests/src/com/android/documentsui/dirlist/TestSelectionEnvironment.java

@@ -100,4 +100,9 @@ public class TestSelectionEnvironment implements SelectionEnvironment {
     public boolean isLayoutItem(int adapterPosition) {
         return false;
     }
+
+    @Override
+    public boolean hasView(int adapterPosition) {
+        return true;
+    }
 }