Adding support for keyboard based drag and drop

For keyboard DnD, we use Accessible DnD implementation.
A placeholder FloatingView draws the focus indicator
for the virtual views

Test: Visible
Bug: 178781566
Change-Id: I632fc7377dffa1e05e3f0a9c3ad18641deb5a1a4
diff --git a/src/com/android/launcher3/DropTargetBar.java b/src/com/android/launcher3/DropTargetBar.java
index ca001a3..c768493 100644
--- a/src/com/android/launcher3/DropTargetBar.java
+++ b/src/com/android/launcher3/DropTargetBar.java
@@ -131,7 +131,10 @@
         int width = MeasureSpec.getSize(widthMeasureSpec);
         int height = MeasureSpec.getSize(heightMeasureSpec);
 
-        if (mIsVertical) {
+        int visibleCount = getVisibleButtonsCount();
+        if (visibleCount == 0) {
+            // do nothing
+        } else if (mIsVertical) {
             int widthSpec = MeasureSpec.makeMeasureSpec(width, MeasureSpec.EXACTLY);
             int heightSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.AT_MOST);
 
@@ -142,7 +145,6 @@
                 }
             }
         } else {
-            int visibleCount = getVisibleButtonsCount();
             int availableWidth = width / visibleCount;
             boolean textVisible = true;
             for (ButtonDropTarget buttons : mDropTargets) {
@@ -165,7 +167,10 @@
 
     @Override
     protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
-        if (mIsVertical) {
+        int visibleCount = getVisibleButtonsCount();
+        if (visibleCount == 0) {
+            // do nothing
+        } else if (mIsVertical) {
             int gap = getResources().getDimensionPixelSize(R.dimen.drop_target_vertical_gap);
             int start = gap;
             int end;
@@ -178,7 +183,6 @@
                 }
             }
         } else {
-            int visibleCount = getVisibleButtonsCount();
             int frameSize = (right - left) / visibleCount;
 
             int start = frameSize / 2;