Reusing viewcontroller in Pagecontrol example

Discussion in 'iOS Programming' started by mrl72, Jan 30, 2011.

  1. mrl72 macrumors regular

    Apr 20, 2008
    I have implemented the lazy load view method from Apple's Pagecontrol sample project in order to create views that are lazy-loaded at run-time as the user flips through each page. Everything works great except now I want to re-use the controllers for another method in my app so that I can share the controllers and views rather than create new ones. The idea is that the user will touch a menu button which shows a particular image gallery using the views and then by selecting another menu button will display and load a new gallery but re-use the controllers. In my code I am doing the following:

    // view controllers are created lazily
    // in the meantime, load the array with placeholders which will be replaced on demand as we flip the page
    -(void)initViewControllers {
        NSMutableArray *controllers = [[NSMutableArray alloc] init];
        for (unsigned i = 0; i < kNumberOfPages; i++)
    		[controllers addObject:[NSNull null]];
        self.viewControllers = controllers;
        [controllers release];
    Then before I call my separate methods I am doing:

    //Clear and init the controllers array
            [viewControllers removeAllObjects];
    	[self initViewControllers];
    And then in each method:

    // replace the placeholder if necessary
        MyViewController *controller = [viewControllers objectAtIndex:page];
        if ((NSNull *)controller == [NSNull null])
            controller = [[MyViewController alloc] init];
            [viewControllers replaceObjectAtIndex:page withObject:controller];
            [controller release];
        // add the controller's view to the scroll view
        if (controller.view.superview == nil)
            CGRect frame = scrollView.frame;
            frame.origin.x = (frame.size.width) * page;
            frame.origin.y = 0;
            controller.view.frame = frame;
            [scrollView addSubview:controller.view];
    But what's happening is if I call my second method it's displaying the views on top of the views that were displayed in my previous method. What I want to do is ensure that before the next method is called all views and its content is destroyed/removed before adding the views again. Can anyone suggest how to do this? I have even tried assigning tags before I add each view but this did not seem to work either.


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