Better focus handling after dismissing task/scrolling.

- When there is no focused task, focus the next task closest to the 
  stack scroll in the focus direction.
- Fixing small regression where no task would focus when alt-tabbing
  because the index was out of bounds.

Change-Id: I2555c9340f40affc371f52d51d88af0eeda53b2e

3 files changed, 24 insertions, 5 deletions

diff --git a/packages/SystemUI/src/com/android/systemui/recents/RecentsActivityLaunchState.java b/packages/SystemUI/src/com/android/systemui/recents/RecentsActivityLaunchState.java
index 82e786140e77..aa1437b28ee8 100644
--- a/packages/SystemUI/src/com/android/systemui/recents/RecentsActivityLaunchState.java
+++ b/packages/SystemUI/src/com/android/systemui/recents/RecentsActivityLaunchState.java
@@ -75,7 +75,7 @@ public class RecentsActivityLaunchState {
             }
 
             // If coming from another app, focus the next task
-            return numTasks - 2;
+            return Math.max(0, numTasks - 2);
         } else {
             if (!launchState.launchedWithAltTab && debugFlags.isFastToggleRecentsEnabled()) {
                 // If fast toggling, defer focusing until the next tap (which will automatically
diff --git a/packages/SystemUI/src/com/android/systemui/recents/views/TaskStackView.java b/packages/SystemUI/src/com/android/systemui/recents/views/TaskStackView.java
index 0ee9caf5be72..1707c4f4ccd0 100644
--- a/packages/SystemUI/src/com/android/systemui/recents/views/TaskStackView.java
+++ b/packages/SystemUI/src/com/android/systemui/recents/views/TaskStackView.java
@@ -964,10 +964,26 @@ public class TaskStackView extends FrameLayout implements TaskStack.TaskStackCal
                 newIndex = (newIndex + (forward ? -1 : 1) + taskCount) % taskCount;
             }
         } else {
-            // We don't have a focused task, so focus the first visible task view
-            TaskView tv = getFrontMostTaskView(stackTasksOnly);
-            if (tv != null) {
-                newIndex = mStack.indexOfStackTask(tv.getTask());
+            // We don't have a focused task
+            float stackScroll = mStackScroller.getStackScroll();
+            ArrayList<Task> tasks = mStack.getStackTasks();
+            int taskCount = tasks.size();
+            if (forward) {
+                // Walk backwards and focus the next task smaller than the current stack scroll
+                for (newIndex = taskCount - 1; newIndex >= 0; newIndex--) {
+                    float taskP = mLayoutAlgorithm.getStackScrollForTask(tasks.get(newIndex));
+                    if (Float.compare(taskP, stackScroll) <= 0) {
+                        break;
+                    }
+                }
+            } else {
+                // Walk forwards and focus the next task larger than the current stack scroll
+                for (newIndex = 0; newIndex < taskCount; newIndex++) {
+                    float taskP = mLayoutAlgorithm.getStackScrollForTask(tasks.get(newIndex));
+                    if (Float.compare(taskP, stackScroll) >= 0) {
+                        break;
+                    }
+                }
             }
         }
         if (newIndex != -1) {
diff --git a/packages/SystemUI/src/com/android/systemui/recents/views/TaskStackViewTouchHandler.java b/packages/SystemUI/src/com/android/systemui/recents/views/TaskStackViewTouchHandler.java
index 47072ba96b6b..fe504fefef26 100644
--- a/packages/SystemUI/src/com/android/systemui/recents/views/TaskStackViewTouchHandler.java
+++ b/packages/SystemUI/src/com/android/systemui/recents/views/TaskStackViewTouchHandler.java
@@ -280,6 +280,9 @@ class TaskStackViewTouchHandler implements SwipeHelper.Callback {
                                 mOverscrollSize);
                         mSv.invalidate();
                     }
+
+                    // Reset the focused task after the user has scrolled
+                    mSv.resetFocusedTask(mSv.getFocusedTask());
                 } else if (mActiveTaskView == null) {
                     // This tap didn't start on a task.
                     maybeHideRecentsFromBackgroundTap((int) ev.getX(), (int) ev.getY());