From 45bee6b24c8d181eafce339dc90d11b5e1bec74e Mon Sep 17 00:00:00 2001
From: Vadim Tryshev <vadimt@google.com>
Date: Mon, 19 Sep 2016 11:00:37 -0700
Subject: [PATCH] For pre-N apps, cascade LOCATION and DROP events.

To restore the pre-N behavior, if a view returns false from its
LOCATION or DROP event handler, the event goes to its parent.

Bug: 31559942
Change-Id: I322099ae1e8a5cbbcf8814f2cd274fbae53b6848
---
 core/java/android/view/View.java         | 13 +++++++++++++
 core/java/android/view/ViewGroup.java    | 17 ++++++++++++-----
 core/java/android/view/ViewRootImpl.java |  4 ++--
 3 files changed, 27 insertions(+), 7 deletions(-)

diff --git a/core/java/android/view/View.java b/core/java/android/view/View.java
index 37b54a87965a9..86d3f62865827 100644
--- a/core/java/android/view/View.java
+++ b/core/java/android/view/View.java
@@ -829,6 +829,17 @@ public class View implements Drawable.Callback, KeyEvent.Callback,
      */
     protected static boolean sPreserveMarginParamsInLayoutParamConversion;
 
+    /**
+     * Prior to N, when drag enters into child of a view that has already received an
+     * ACTION_DRAG_ENTERED event, the parent doesn't get a ACTION_DRAG_EXITED event.
+     * ACTION_DRAG_LOCATION and ACTION_DROP were delivered to the parent of a view that returned
+     * false from its event handler for these events.
+     * Starting from N, the parent will get ACTION_DRAG_EXITED event before the child gets its
+     * ACTION_DRAG_ENTERED. ACTION_DRAG_LOCATION and ACTION_DROP are never propagated to the parent.
+     * sCascadedDragDrop is true for pre-N apps for backwards compatibility implementation.
+     */
+    static boolean sCascadedDragDrop;
+
     /**
      * This view does not want keystrokes. Use with TAKES_FOCUS_MASK when
      * calling setFlags.
@@ -4065,6 +4076,8 @@ public class View implements Drawable.Callback, KeyEvent.Callback,
             // in apps so we target check it to avoid breaking existing apps.
             sPreserveMarginParamsInLayoutParamConversion = targetSdkVersion >= N;
 
+            sCascadedDragDrop = targetSdkVersion < N;
+
             sCompatibilityDone = true;
         }
     }
diff --git a/core/java/android/view/ViewGroup.java b/core/java/android/view/ViewGroup.java
index 7111f28f5741b..d4b7d3bdd76aa 100644
--- a/core/java/android/view/ViewGroup.java
+++ b/core/java/android/view/ViewGroup.java
@@ -1451,7 +1451,7 @@ public abstract class ViewGroup extends View implements ViewParent, ViewManager
             View target = findFrontmostDroppableChildAt(event.mX, event.mY, localPoint);
 
             if (target != mCurrentDragChild) {
-                if (mContext.getApplicationInfo().targetSdkVersion < Build.VERSION_CODES.N) {
+                if (sCascadedDragDrop) {
                     // For pre-Nougat apps, make sure that the whole hierarchy of views that contain
                     // the drag location is kept in the state between ENTERED and EXITED events.
                     // (Starting with N, only the innermost view will be in that state).
@@ -1494,10 +1494,17 @@ public abstract class ViewGroup extends View implements ViewParent, ViewManager
                     event.mX = tx;
                     event.mY = ty;
 
-                    if (!event.mEventHandlerWasCalled && mIsInterestedInDrag) {
-                        // The child didn't invoke any event handler, but this view is interested in
-                        // drag, so the event goes to this view.
-                        retval = super.dispatchDragEvent(event);
+                    if (mIsInterestedInDrag) {
+                        final boolean eventWasConsumed;
+                        if (sCascadedDragDrop) {
+                            eventWasConsumed = retval;
+                        } else {
+                            eventWasConsumed = event.mEventHandlerWasCalled;
+                        }
+
+                        if (!eventWasConsumed) {
+                            retval = super.dispatchDragEvent(event);
+                        }
                     }
                 } else {
                     retval = super.dispatchDragEvent(event);
diff --git a/core/java/android/view/ViewRootImpl.java b/core/java/android/view/ViewRootImpl.java
index 0f161cdbc900e..e95fa5e6a2ee1 100644
--- a/core/java/android/view/ViewRootImpl.java
+++ b/core/java/android/view/ViewRootImpl.java
@@ -5524,7 +5524,7 @@ public final class ViewRootImpl implements ViewParent,
                 // A direct EXITED event means that the window manager knows we've just crossed
                 // a window boundary, so the current drag target within this one must have
                 // just been exited. Send the EXITED notification to the current drag view, if any.
-                if (mTargetSdkVersion < Build.VERSION_CODES.N) {
+                if (View.sCascadedDragDrop) {
                     mView.dispatchDragEnterExitInPreN(event);
                 }
                 setDragFocus(null, event);
@@ -5644,7 +5644,7 @@ public final class ViewRootImpl implements ViewParent,
     }
 
     public void setDragFocus(View newDragTarget, DragEvent event) {
-        if (mCurrentDragView != newDragTarget && mTargetSdkVersion >= Build.VERSION_CODES.N) {
+        if (mCurrentDragView != newDragTarget && !View.sCascadedDragDrop) {
             // Send EXITED and ENTERED notifications to the old and new drag focus views.
 
             final float tx = event.mX;