Fix all apps tab fling detection

It is a regression when we changed from ViewPager to PagedView.
Unlike ViewPager, PagedView does not take "yDiff" into account
when determining should it intercept its child MotionEvent.

Override determineScrollingStart, just like what we did in Workspace

Change-Id: I25f7415c45c370629558d944f59bf95c741b9319
FIX: 73878167

2 files changed, 40 insertions, 1 deletions

diff --git a/src/com/android/launcher3/PagedView.java b/src/com/android/launcher3/PagedView.java
index ccb0a955d..4be32b207 100644
--- a/src/com/android/launcher3/PagedView.java
+++ b/src/com/android/launcher3/PagedView.java
@@ -1892,6 +1892,14 @@ public abstract class PagedView<T extends View & PageIndicator> extends ViewGrou
                 getNextPage() + 1, getChildCount());
     }
 
+    protected float getDownMotionX() {
+        return mDownMotionX;
+    }
+
+    protected float getDownMotionY() {
+        return mDownMotionY;
+    }
+
     @Override
     public boolean onHoverEvent(android.view.MotionEvent event) {
         return true;
diff --git a/src/com/android/launcher3/allapps/AllAppsPagedView.java b/src/com/android/launcher3/allapps/AllAppsPagedView.java
index 86186fdb5..3b4450bf8 100644
--- a/src/com/android/launcher3/allapps/AllAppsPagedView.java
+++ b/src/com/android/launcher3/allapps/AllAppsPagedView.java
@@ -18,12 +18,17 @@ package com.android.launcher3.allapps;
 import android.content.Context;
 import android.util.AttributeSet;
 
+import android.view.MotionEvent;
 import com.android.launcher3.PagedView;
 import com.android.launcher3.R;
 
 public class AllAppsPagedView extends PagedView<PersonalWorkSlidingTabStrip> {
 
-    public AllAppsPagedView(Context context) {
+  final static float START_DAMPING_TOUCH_SLOP_ANGLE = (float) Math.PI / 6;
+  final static float MAX_SWIPE_ANGLE = (float) Math.PI / 3;
+  final static float TOUCH_SLOP_DAMPING_FACTOR = 4;
+
+  public AllAppsPagedView(Context context) {
         this(context, null);
     }
 
@@ -46,4 +51,30 @@ public class AllAppsPagedView extends PagedView<PersonalWorkSlidingTabStrip> {
         super.onScrollChanged(l, t, oldl, oldt);
         mPageIndicator.setScroll(l, mMaxScrollX);
     }
+
+    @Override
+    protected void determineScrollingStart(MotionEvent ev) {
+        float absDeltaX = Math.abs(ev.getX() - getDownMotionX());
+        float absDeltaY = Math.abs(ev.getY() - getDownMotionY());
+
+        if (Float.compare(absDeltaX, 0f) == 0) return;
+
+        float slope = absDeltaY / absDeltaX;
+        float theta = (float) Math.atan(slope);
+
+        if (absDeltaX > mTouchSlop || absDeltaY > mTouchSlop) {
+            cancelCurrentPageLongPress();
+        }
+
+        if (theta > MAX_SWIPE_ANGLE) {
+            return;
+        } else if (theta > START_DAMPING_TOUCH_SLOP_ANGLE) {
+            theta -= START_DAMPING_TOUCH_SLOP_ANGLE;
+            float extraRatio = (float)
+                    Math.sqrt((theta / (MAX_SWIPE_ANGLE - START_DAMPING_TOUCH_SLOP_ANGLE)));
+            super.determineScrollingStart(ev, 1 + TOUCH_SLOP_DAMPING_FACTOR * extraRatio);
+        } else {
+            super.determineScrollingStart(ev);
+        }
+    }
 }