Defer loading off-screen pages. The current behavior preloads off-scr…

…een synchronously before displaying the current page incurring unnecessary latency.
developeral · Jul 11, 2014 · a97cebe · a97cebe
1 parent 3f3013c
commit a97cebe
Showing 1 changed file with 14 additions and 7 deletions.
diff --git a/src/pagingscrollview/src/NIPagingScrollView.m b/src/pagingscrollview/src/NIPagingScrollView.m
@@ -311,6 +311,16 @@ - (void)recyclePageAtIndex:(NSInteger)pageIndex {
   }
 }
 
+- (void)preloadOffscreenPages {
+  NSRange rangeOfVisiblePages = [self rangeOfVisiblePages];
+  for (NSUInteger pageIndex = rangeOfVisiblePages.location;
+       pageIndex < NSMaxRange(rangeOfVisiblePages); ++pageIndex) {
+    if (![self isDisplayingPageForIndex:pageIndex]) {
+      [self displayPageAtIndex:pageIndex];
+    }
+  }
+}
+
 - (void)updateVisiblePagesShouldNotifyDelegate:(BOOL)shouldNotifyDelegate {
   // Before updating _centerPageIndex, notify delegate
   if (shouldNotifyDelegate && (self.numberOfPages > 0) &&
@@ -345,13 +355,10 @@ - (void)updateVisiblePagesShouldNotifyDelegate:(BOOL)shouldNotifyDelegate {
       [self displayPageAtIndex:_centerPageIndex];
     }
 
-    // Add missing pages.
-    for (NSUInteger pageIndex = rangeOfVisiblePages.location;
-         pageIndex < NSMaxRange(rangeOfVisiblePages); ++pageIndex) {
-      if (![self isDisplayingPageForIndex:pageIndex]) {
-        [self displayPageAtIndex:pageIndex];
-      }
-    }
+    // Add missing pages after displaying the current page.
+    [self performSelector:@selector(preloadOffscreenPages)
+               withObject:nil
+               afterDelay:0];
   } else {
     _centerPageIndex = -1;
   }