ViewPager patch to allow the adapter not know the exact number of items, only two adjoining ones

ViewPagerInexact.patch.java

/*
This patch lets a ViewPagerAdapter{subclass} not know the exact number of items, and only keep prev and next.

- Return some arbitrary large number from getCount
- Maintain prev and next data items (not whole list)
- In instantiateItem, return null for item positions other than prev/next, or when there is no prev/next item

With this patch, ViewPager will notice the "null"'s and treat them like "end of list" markers.
*/

diff -r dfe398558897 AquaSupport/src/android/support/v4/view/ViewPagerEx.java
--- a/AquaSupport/src/android/support/v4/view/ViewPagerEx.java	Thu Nov 19 17:56:39 2015 +0300
+++ b/AquaSupport/src/android/support/v4/view/ViewPagerEx.java	Thu Nov 19 21:55:58 2015 +0300
@@ -1311,7 +1311,22 @@
 		float offset = curItem.offset;
 		int pos = curItem.position - 1;
 		mFirstOffset = curItem.position == 0 ? curItem.offset : -Float.MAX_VALUE;
-		mLastOffset = curItem.position == N - 1 ? curItem.offset + curItem.widthFactor - 1 : Float.MAX_VALUE;
+		// kman begin
+		if (curItem.position == 0) {
+			mFirstOffset = curItem.offset;
+		} else if (curIndex > 0 && mItems.get(curIndex - 1).object == null) {
+			mFirstOffset = curItem.offset;
+		} else {
+			mFirstOffset = -Float.MAX_VALUE;
+		}
+		if (curItem.position == N - 1) {
+			mLastOffset = curItem.offset + curItem.widthFactor - 1;
+		} else if (curIndex < itemCount - 1 && mItems.get(curIndex + 1).object == null) {
+			mLastOffset = curItem.offset + curItem.widthFactor - 1;
+		} else {
+			mLastOffset = Float.MAX_VALUE;
+		}
+		// kman end
 		// Previous pages
 		for (int i = curIndex - 1; i >= 0; i--, pos--) {
 			final ItemInfo ii = mItems.get(i);
@@ -2220,10 +2235,22 @@
 		if (firstItem.position != 0) {
 			leftAbsolute = false;
 			leftBound = firstItem.offset * width;
+			// kman begin
+			if (firstItem.object == null) {
+				leftAbsolute = true;
+				leftBound = width * mFirstOffset;
+			}
+			// kman end
 		}
 		if (lastItem.position != mAdapter.getCount() - 1) {
 			rightAbsolute = false;
 			rightBound = lastItem.offset * width;
+			// kman begin
+			if (lastItem.object == null) {
+				rightAbsolute = true;
+				rightBound = width * mLastOffset;
+			}
+			// kman end
 		}
 
 		if (scrollX < leftBound) {
@@ -2308,6 +2335,16 @@
 
 			// Only let the user target pages we have items for
 			targetPage = Math.max(firstItem.position, Math.min(targetPage, lastItem.position));
+
+			// kman
+			if (lastItem.position == targetPage && lastItem.object == null) {
+				targetPage = currentPage;
+			} else if (firstItem.position == targetPage && firstItem.object == null) {
+				targetPage = currentPage;
+			}
+		} else {
+			// kman
+			targetPage = currentPage;
 		}
 
 		return targetPage;