Add transient state tracking to Views

Transient state is temporary bookkeeping that Views need to perform
that the app should not need to be aware of. Examples include text
selection regions and animation state.

Transient state is a problem for AdapterViews like ListView that do
view recycling. Unless the app takes responsibility for tracking and
restoring transient state as if it were a part of the adapter's data
set, it cannot correctly recycle views. Selections disappear when an
EditText is scrolled out of sight and animations seem to play on the
wrong views.

Views can now flag themselves as having transient state. (As the name
implies, this should be a temporary condition.) If a ViewGroup
contains a child with transient state, that ViewGroup also has
transient state.

AbsListView's recycler now tracks views with transient state
separately. Views with transient state will be retained, and until a
data set change occurs the same view will be reused for that position
instead of calling the adapter's getView() method.

The API to set and check transient state is currently hidden.

Change-Id: Idfd8eaac2c548337686d8d9f98fda4c64be5b8a0

8 files changed, 229 insertions, 12 deletions

diff --git a/core/java/android/view/View.java b/core/java/android/view/View.java
index 32f5732..c16eb31 100644
--- a/core/java/android/view/View.java
+++ b/core/java/android/view/View.java
@@ -1759,6 +1759,16 @@ public class View implements Drawable.Callback, Drawable.Callback2, KeyEvent.Cal
     static final int LAYOUT_DIRECTION_RESOLVED = 0x00000008;
 
 
+    /**
+     * Indicates that the view is tracking some sort of transient state
+     * that the app should not need to be aware of, but that the framework
+     * should take special care to preserve.
+     *
+     * @hide
+     */
+    static final int HAS_TRANSIENT_STATE = 0x00000010;
+
+
     /* End of masks for mPrivateFlags2 */
 
     static final int DRAG_MASK = DRAG_CAN_ACCEPT | DRAG_HOVERED;
@@ -4889,6 +4899,43 @@ public class View implements Drawable.Callback, Drawable.Callback2, KeyEvent.Cal
     }
 
     /**
+     * Indicates whether the view is currently tracking transient state that the
+     * app should not need to concern itself with saving and restoring, but that
+     * the framework should take special note to preserve when possible.
+     *
+     * @return true if the view has transient state
+     *
+     * @hide
+     */
+    @ViewDebug.ExportedProperty(category = "layout")
+    public boolean hasTransientState() {
+        return (mPrivateFlags2 & HAS_TRANSIENT_STATE) == HAS_TRANSIENT_STATE;
+    }
+
+    /**
+     * Set whether this view is currently tracking transient state that the
+     * framework should attempt to preserve when possible.
+     *
+     * @param hasTransientState true if this view has transient state
+     *
+     * @hide
+     */
+    public void setHasTransientState(boolean hasTransientState) {
+        if (hasTransientState() == hasTransientState) return;
+
+        mPrivateFlags2 = (mPrivateFlags2 & ~HAS_TRANSIENT_STATE) |
+                (hasTransientState ? HAS_TRANSIENT_STATE : 0);
+        if (mParent != null) {
+            try {
+                mParent.childHasTransientStateChanged(this, hasTransientState);
+            } catch (AbstractMethodError e) {
+                Log.e(VIEW_LOG_TAG, mParent.getClass().getSimpleName() +
+                        " does not fully implement ViewParent", e);
+            }
+        }
+    }
+
+    /**
      * If this view doesn't do any drawing on its own, set this flag to
      * allow further optimizations. By default, this flag is not set on
      * View, but could be set on some View subclasses such as ViewGroup.
diff --git a/core/java/android/view/ViewGroup.java b/core/java/android/view/ViewGroup.java
index f2935e8..ac46d4e 100644
--- a/core/java/android/view/ViewGroup.java
+++ b/core/java/android/view/ViewGroup.java
@@ -77,6 +77,7 @@ import java.util.HashSet;
  * @attr ref android.R.styleable#ViewGroup_animateLayoutChanges
  */
 public abstract class ViewGroup extends View implements ViewParent, ViewManager {
+    private static final String TAG = "ViewGroup";
 
     private static final boolean DBG = false;
 
@@ -375,6 +376,10 @@ public abstract class ViewGroup extends View implements ViewParent, ViewManager
     @ViewDebug.ExportedProperty(category = "drawing")
     boolean mDrawLayers = true;
 
+    // Indicates how many of this container's child subtrees contain transient state
+    @ViewDebug.ExportedProperty(category = "layout")
+    private int mChildCountWithTransientState = 0;
+
     public ViewGroup(Context context) {
         super(context);
         initViewGroup();
@@ -653,6 +658,38 @@ public abstract class ViewGroup extends View implements ViewParent, ViewManager
     }
 
     /**
+     * Called when a child view has changed whether or not it is tracking transient state.
+     *
+     * @hide
+     */
+    public void childHasTransientStateChanged(View child, boolean childHasTransientState) {
+        final boolean oldHasTransientState = hasTransientState();
+        if (childHasTransientState) {
+            mChildCountWithTransientState++;
+        } else {
+            mChildCountWithTransientState--;
+        }
+
+        final boolean newHasTransientState = hasTransientState();
+        if (mParent != null && oldHasTransientState != newHasTransientState) {
+            try {
+                mParent.childHasTransientStateChanged(this, newHasTransientState);
+            } catch (AbstractMethodError e) {
+                Log.e(TAG, mParent.getClass().getSimpleName() +
+                        " does not fully implement ViewParent", e);
+            }
+        }
+    }
+
+    /**
+     * @hide
+     */
+    @Override
+    public boolean hasTransientState() {
+        return mChildCountWithTransientState > 0 || super.hasTransientState();
+    }
+
+    /**
      * {@inheritDoc}
      */
     @Override
@@ -3099,6 +3136,10 @@ public abstract class ViewGroup extends View implements ViewParent, ViewManager
         if ((child.mViewFlags & DUPLICATE_PARENT_STATE) == DUPLICATE_PARENT_STATE) {
             mGroupFlags |= FLAG_NOTIFY_CHILDREN_ON_DRAWABLE_STATE_CHANGE;
         }
+
+        if (child.hasTransientState()) {
+            childHasTransientStateChanged(child, true);
+        }
     }
 
     private void addInArray(View child, int index) {
@@ -3295,6 +3336,10 @@ public abstract class ViewGroup extends View implements ViewParent, ViewManager
            view.dispatchDetachedFromWindow();
         }
 
+        if (view.hasTransientState()) {
+            childHasTransientStateChanged(view, false);
+        }
+
         onViewRemoved(view);
 
         needGlobalAttributesUpdate(false);
@@ -3366,6 +3411,10 @@ public abstract class ViewGroup extends View implements ViewParent, ViewManager
                view.dispatchDetachedFromWindow();
             }
 
+            if (view.hasTransientState()) {
+                childHasTransientStateChanged(view, false);
+            }
+
             needGlobalAttributesUpdate(false);
 
             onViewRemoved(view);
@@ -3431,6 +3480,10 @@ public abstract class ViewGroup extends View implements ViewParent, ViewManager
                view.dispatchDetachedFromWindow();
             }
 
+            if (view.hasTransientState()) {
+                childHasTransientStateChanged(view, false);
+            }
+
             onViewRemoved(view);
 
             view.mParent = null;
@@ -3471,6 +3524,10 @@ public abstract class ViewGroup extends View implements ViewParent, ViewManager
             child.dispatchDetachedFromWindow();
         }
 
+        if (child.hasTransientState()) {
+            childHasTransientStateChanged(child, false);
+        }
+
         onViewRemoved(child);
     }
 
diff --git a/core/java/android/view/ViewParent.java b/core/java/android/view/ViewParent.java
index 873d4bb..8395f1b 100644
--- a/core/java/android/view/ViewParent.java
+++ b/core/java/android/view/ViewParent.java
@@ -261,4 +261,14 @@ public interface ViewParent {
      * @return True if the event was sent.
      */
     public boolean requestSendAccessibilityEvent(View child, AccessibilityEvent event);
+
+    /**
+     * Called when a child view now has or no longer is tracking transient state.
+     *
+     * @param child Child view whose state has changed
+     * @param hasTransientState true if this child has transient state
+     *
+     * @hide
+     */
+    public void childHasTransientStateChanged(View child, boolean hasTransientState);
 }
diff --git a/core/java/android/view/ViewRootImpl.java b/core/java/android/view/ViewRootImpl.java
index d41d168..84ce2a4 100644
--- a/core/java/android/view/ViewRootImpl.java
+++ b/core/java/android/view/ViewRootImpl.java
@@ -4144,6 +4144,10 @@ public final class ViewRootImpl implements ViewParent,
         return scrollToRectOrFocus(rectangle, immediate);
     }
 
+    public void childHasTransientStateChanged(View child, boolean hasTransientState) {
+        // Do nothing.
+    }
+
     class TakenSurfaceHolder extends BaseSurfaceHolder {
         @Override
         public boolean onAllowLockCanvas() {
diff --git a/core/java/android/widget/AbsListView.java b/core/java/android/widget/AbsListView.java
index e94b1cb..e7bc1e1 100644
--- a/core/java/android/widget/AbsListView.java
+++ b/core/java/android/widget/AbsListView.java
@@ -36,6 +36,7 @@ import android.text.TextWatcher;
 import android.util.AttributeSet;
 import android.util.Log;
 import android.util.LongSparseArray;
+import android.util.SparseArray;
 import android.util.SparseBooleanArray;
 import android.util.StateSet;
 import android.view.ActionMode;
@@ -87,6 +88,8 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te
         ViewTreeObserver.OnTouchModeChangeListener,
         RemoteViewsAdapter.RemoteAdapterConnectionCallback {
 
+    private static final String TAG = "AbsListView";
+
     /**
      * Disables the transcript mode.
      *
@@ -263,6 +266,11 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te
     private RemoteViewsAdapter mRemoteAdapter;
 
     /**
+     * If mAdapter != null, whenever this is true the adapter has stable IDs.
+     */
+    boolean mAdapterHasStableIds;
+
+    /**
      * This flag indicates the a full notify is required when the RemoteViewsAdapter connects
      */
     private boolean mDeferNotifyDataSetChanged = false;
@@ -812,7 +820,8 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te
     @Override
     public void setAdapter(ListAdapter adapter) {
         if (adapter != null) {
-            if (mChoiceMode != CHOICE_MODE_NONE && mAdapter.hasStableIds() &&
+            mAdapterHasStableIds = mAdapter.hasStableIds();
+            if (mChoiceMode != CHOICE_MODE_NONE && mAdapterHasStableIds &&
                     mCheckedIdStates == null) {
                 mCheckedIdStates = new LongSparseArray<Integer>();
             }
@@ -2011,6 +2020,11 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te
         isScrap[0] = false;
         View scrapView;
 
+        scrapView = mRecycler.getTransientStateView(position);
+        if (scrapView != null) {
+            return scrapView;
+        }
+
         scrapView = mRecycler.getScrapView(position);
 
         View child;
@@ -2021,6 +2035,13 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te
             }
 
             child = mAdapter.getView(position, scrapView, this);
+            if (mAdapterHasStableIds) {
+                LayoutParams lp = (LayoutParams) child.getLayoutParams();
+                if (lp == null) {
+                    lp = (LayoutParams) generateDefaultLayoutParams();
+                }
+                lp.itemId = mAdapter.getItemId(position);
+            }
 
             if (ViewDebug.TRACE_RECYCLER) {
                 ViewDebug.trace(child, ViewDebug.RecyclerTraceType.BIND_VIEW,
@@ -4543,7 +4564,9 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te
 
         if (count > 0) {
             detachViewsFromParent(start, count);
+            mRecycler.removeSkippedScrap();
         }
+
         offsetChildrenTopAndBottom(incrementalDeltaY);
 
         if (down) {
@@ -4853,6 +4876,9 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te
             confirmCheckedPositionsById();
         }
 
+        // TODO: In the future we can recycle these views based on stable ID instead.
+        mRecycler.clearTransientStateViews();
+
         if (count > 0) {
             int newPos;
             int selectablePos;
@@ -5735,6 +5761,11 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te
          */
         int scrappedFromPosition;
 
+        /**
+         * The ID the view represents
+         */
+        long itemId = -1;
+
         public LayoutParams(Context c, AttributeSet attrs) {
             super(c, attrs);
         }
@@ -5807,6 +5838,10 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te
 
         private ArrayList<View> mCurrentScrap;
 
+        private ArrayList<View> mSkippedScrap;
+
+        private SparseArray<View> mTransientStateViews;
+
         public void setViewTypeCount(int viewTypeCount) {
             if (viewTypeCount < 1) {
                 throw new IllegalArgumentException("Can't have a viewTypeCount < 1");
@@ -5838,6 +5873,12 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te
                     }
                 }
             }
+            if (mTransientStateViews != null) {
+                final int count = mTransientStateViews.size();
+                for (int i = 0; i < count; i++) {
+                    mTransientStateViews.valueAt(i).forceLayout();
+                }
+            }
         }
 
         public boolean shouldRecycleViewType(int viewType) {
@@ -5864,6 +5905,9 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te
                     }
                 }
             }
+            if (mTransientStateViews != null) {
+                mTransientStateViews.clear();
+            }
         }
 
         /**
@@ -5910,6 +5954,28 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te
             return null;
         }
 
+        View getTransientStateView(int position) {
+            if (mTransientStateViews == null) {
+                return null;
+            }
+            final int index = mTransientStateViews.indexOfKey(position);
+            if (index < 0) {
+                return null;
+            }
+            final View result = mTransientStateViews.valueAt(index);
+            mTransientStateViews.removeAt(index);
+            return result;
+        }
+
+        /**
+         * Dump any currently saved views with transient state.
+         */
+        void clearTransientStateViews() {
+            if (mTransientStateViews != null) {
+                mTransientStateViews.clear();
+            }
+        }
+
         /**
          * @return A view from the ScrapViews collection. These are unordered.
          */
@@ -5926,7 +5992,7 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te
         }
 
         /**
-         * Put a view into the ScapViews list. These views are unordered.
+         * Put a view into the ScrapViews list. These views are unordered.
          *
          * @param scrap The view to add
          */
@@ -5936,23 +6002,32 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te
                 return;
             }
 
+            lp.scrappedFromPosition = position;
+
             // Don't put header or footer views or views that should be ignored
             // into the scrap heap
             int viewType = lp.viewType;
-            if (!shouldRecycleViewType(viewType)) {
-                if (viewType != ITEM_VIEW_TYPE_HEADER_OR_FOOTER) {
-                    removeDetachedView(scrap, false);
+            final boolean scrapHasTransientState = scrap.hasTransientState();
+            if (!shouldRecycleViewType(viewType) || scrapHasTransientState) {
+                if (viewType != ITEM_VIEW_TYPE_HEADER_OR_FOOTER || scrapHasTransientState) {
+                    if (mSkippedScrap == null) {
+                        mSkippedScrap = new ArrayList<View>();
+                    }
+                    mSkippedScrap.add(scrap);
+                }
+                if (scrapHasTransientState) {
+                    if (mTransientStateViews == null) {
+                        mTransientStateViews = new SparseArray<View>();
+                    }
+                    mTransientStateViews.put(position, scrap);
                 }
                 return;
             }
 
-            lp.scrappedFromPosition = position;
-
+            scrap.dispatchStartTemporaryDetach();
             if (mViewTypeCount == 1) {
-                scrap.dispatchStartTemporaryDetach();
                 mCurrentScrap.add(scrap);
             } else {
-                scrap.dispatchStartTemporaryDetach();
                 mScrapViews[viewType].add(scrap);
             }
 
@@ -5962,6 +6037,20 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te
         }
 
         /**
+         * Finish the removal of any views that skipped the scrap heap.
+         */
+        void removeSkippedScrap() {
+            if (mSkippedScrap == null) {
+                return;
+            }
+            final int count = mSkippedScrap.size();
+            for (int i = 0; i < count; i++) {
+                removeDetachedView(mSkippedScrap.get(i), false);
+            }
+            mSkippedScrap.clear();
+        }
+
+        /**
          * Move all views remaining in mActiveViews to mScrapViews.
          */
         void scrapActiveViews() {
@@ -5980,11 +6069,19 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te
 
                     activeViews[i] = null;
 
-                    if (!shouldRecycleViewType(whichScrap)) {
+                    final boolean scrapHasTransientState = victim.hasTransientState();
+                    if (!shouldRecycleViewType(whichScrap) || scrapHasTransientState) {
                         // Do not move views that should be ignored
-                        if (whichScrap != ITEM_VIEW_TYPE_HEADER_OR_FOOTER) {
+                        if (whichScrap != ITEM_VIEW_TYPE_HEADER_OR_FOOTER ||
+                                scrapHasTransientState) {
                             removeDetachedView(victim, false);
                         }
+                        if (scrapHasTransientState) {
+                            if (mTransientStateViews == null) {
+                                mTransientStateViews = new SparseArray<View>();
+                            }
+                            mTransientStateViews.put(mFirstActivePosition + i, victim);
+                        }
                         continue;
                     }
 
diff --git a/core/java/android/widget/EdgeEffect.java b/core/java/android/widget/EdgeEffect.java
index 326587e..83aa8ba 100644
--- a/core/java/android/widget/EdgeEffect.java
+++ b/core/java/android/widget/EdgeEffect.java
@@ -56,7 +56,7 @@ public class EdgeEffect {
     // Time it will take in ms for a pulled glow to decay to partial strength before release
     private static final int PULL_DECAY_TIME = 1000;
 
-    private static final float MAX_ALPHA = 0.8f;
+    private static final float MAX_ALPHA = 1.f;
     private static final float HELD_EDGE_ALPHA = 0.7f;
     private static final float HELD_EDGE_SCALE_Y = 0.5f;
     private static final float HELD_GLOW_ALPHA = 0.5f;
diff --git a/core/java/android/widget/GridView.java b/core/java/android/widget/GridView.java
index be2df8e..6bc5a15 100644
--- a/core/java/android/widget/GridView.java
+++ b/core/java/android/widget/GridView.java
@@ -1205,6 +1205,7 @@ public class GridView extends AbsListView {
             // Clear out old views
             //removeAllViewsInLayout();
             detachAllViewsFromParent();
+            recycleBin.removeSkippedScrap();
 
             switch (mLayoutMode) {
             case LAYOUT_SET_SELECTION:
diff --git a/core/java/android/widget/ListView.java b/core/java/android/widget/ListView.java
index 67fd059..46c2c07 100644
--- a/core/java/android/widget/ListView.java
+++ b/core/java/android/widget/ListView.java
@@ -1591,6 +1591,7 @@ public class ListView extends AbsListView {
 
             // Clear out old views
             detachAllViewsFromParent();
+            recycleBin.removeSkippedScrap();
 
             switch (mLayoutMode) {
             case LAYOUT_SET_SELECTION: