CCScrollLayer doesn't call delegate method when [scrollLayer selectPage:1];

[draganjovev]

Steps to reproduce issue

scrollLayer = [[CCScrollLayer alloc] initWithLayers:someLayers
widthOffset:0];
[scrollLayer selectPage:1];
[scrollLayer setDelegate:self];
[self addChild:scrollLayer];

• (void) scrollLayer: (CCScrollLayer *) sender scrolledToPageNumber: (int) page {
  NSLog(@"Delegate called");
  }

Since you're on page 1, try to go to page 0 and you will see that delegate method is not called because currentScreen_ and prevScreen_ are equal.

Solution si to replace line 119 to

currentScreen_ = NSNotFound;

[liamoreilly]

I can confirm this bug. Although the line number in the previous post has changed with the current version.

[liamoreilly]

To Clarify. draganjovev is correct, but I disagree with his solution. His solution results in the following odd behaviour. If you setup the use case as he describes and slightly try to scroll (but make sure the page lands on the same one - i.e. no actual change page occurs) then the delegate gets fired when it should not get fired.

I propose that the solution is to swap lines 291 and 292 in -(void) selectPage:(int)page. That was the current page and previous page are recorded as the same when you use this method. If you then manually change page the delegate gets fired, but it you happen to nudge the page and it moves back to center (no page change really occurred), then the delegate wont get fired.

For completeness the method now looks like:

-(void) selectPage:(int)page
{
    if (page < 0 || page >= [layers_ count]) {
        CCLOGERROR(@"CCScrollLayer#selectPage: %d - wrong page number, out of bounds. ", page);
        return;
    }

    self.position = [self positionForPageWithNumber: page];

    // Original:
    // prevScreen_ = currentScreen_;
    // currentScreen_ = page;

    // My solution:
    currentScreen_ = page;
    prevScreen_ = currentScreen_;   
}

[KerryBatts]

I tested and confirmed the bug and also aliam13's fix.