Fix horizontal fling

The horizontal flinging was broken because the 'canScrollHorizontally' used the left and right direction incorrectly. This combined with the missing negation in 'clampViewPositionHorizontal' caused the scrolling to work, but flinging to fail.

Author: AlexKolpa

library/src/main/java/com/liuguangqiang/swipeback/SwipeBackLayout.java

@@ -274,11 +274,11 @@ public boolean canChildScrollDown() {
     }
 
     private boolean canChildScrollRight() {
-        return ViewCompat.canScrollHorizontally(scrollChild, -1);
+        return ViewCompat.canScrollHorizontally(scrollChild, 1);
     }
 
     private boolean canChildScrollLeft() {
-        return ViewCompat.canScrollHorizontally(scrollChild, 1);
+        return ViewCompat.canScrollHorizontally(scrollChild, -1);
     }
 
     private void finish() {
@@ -327,11 +327,11 @@ public int clampViewPositionHorizontal(View child, int left, int dx) {
 
             int result = 0;
 
-            if (dragEdge == DragEdge.LEFT && !canChildScrollRight() && left > 0) {
+            if (dragEdge == DragEdge.LEFT && !canChildScrollLeft() && left > 0) {
                 final int leftBound = getPaddingLeft();
                 final int rightBound = horizontalDragRange;
                 result = Math.min(Math.max(left, leftBound), rightBound);
-            } else if (dragEdge == DragEdge.RIGHT && !canChildScrollLeft() && left < 0) {
+            } else if (dragEdge == DragEdge.RIGHT && !canChildScrollRight() && left < 0) {
                 final int leftBound = -horizontalDragRange;
                 final int rightBound = getPaddingLeft();
                 result = Math.min(Math.max(left, leftBound), rightBound);