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Compatible with
  • iOS

AMScrollingNavbar 2.0.9.0

Xamarin Inc

A custom UINavigationController that enables the scrolling of the navigation bar alongside the scrolling of an observed content view

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AMScrollingNavbar provides a custom UINavigationController that enables the scrolling of the navigation bar alongside the scrolling of an observed content view.

Usage

Make sure to use a subclass of ScrollingNavigationController for your UINavigationController. Either set the class of your UINavigationController in your storyboard, or create programmatically a ScrollingNavigationController instance in your code.

Use the FollowScrollView() method to start following the scrolling of a scrollable view (e.g.: a UIScrollView or UITableView):

public override void ViewDidAppear (bool animated)
{
    base.ViewDidAppear (animated);

    var scrolling = NavigationController as ScrollingNavigationController;
    if (scrolling != null) {
        // Enable the navbar scrolling
        scrolling.FollowScrollView (scrollView, 100.0);
    }
}

Use the StopFollowingScrollview() method to stop the behaviour. Remember to call this function on disappear:

public override void ViewDidDisappear (bool animated)
{
    base.ViewDidDisappear (animated);

    var scrolling = NavigationController as ScrollingNavigationController;
    if (scrolling != null) {
        scrolling.StopFollowingScrollView (true);
    }
}

As the navigation bar may be hidden, we should make sure to show it whenever the view is about to disappear:

public override void ViewWillDisappear (bool animated)
{
    base.ViewWillDisappear (animated);

    var scrolling = NavigationController as ScrollingNavigationController;
    if (scrolling != null) {
        scrolling.ShowNavbar (true);
    }
}

StateChanged Event

You can attach an event handler to receive a call when the state of the navigation bar changes:

public override void ViewDidAppear (bool animated)
{
    base.ViewDidAppear (animated);

    var scrolling = NavigationController as ScrollingNavigationController;
    if (scrolling != null) {
        scrolling.StateChanged += OnStateChanged;
    }
}

Similar to attaching the behaviour, you should detach the event on disappear:

public override void ViewWillDisappear (bool animated)
{
    base.ViewWillDisappear (animated);

    var scrolling = NavigationController as ScrollingNavigationController;
    if (scrolling != null) {
        scrolling.StateChanged -= OnStateChanged;
    }
}

Scrolling To Top

When the user taps the status bar, by default a scrollable view scrolls to the top of its content. If you want to also show the navigation bar, make sure implement the IUIScrollViewDelegate interface and include this in your controller:

[Export ("scrollViewShouldScrollToTop:")]
public bool ShouldScrollToTop (UIScrollView scrollView)
{
    var scrolling = NavigationController as ScrollingNavigationController;
    if (scrolling != null) {
        scrolling.ShowNavbar (true);
    }
    return true;
}

You then need to attach this method to the scroll view:

// for UIScrollView
scrollView.ShouldScrollToTop = ShouldScrollToTop;

// for UIWebView
webView.ScrollView.ShouldScrollToTop = ShouldScrollToTop;

Nothing has to be done for a UITableViewController as it will automatically pick up the method.

ScrollingNavigationViewController & ScrollingNavigationTableViewController

To DRY things up you can let your view controller subclass ScrollingNavigationViewController or ScrollingNavigationViewController, which provide the base setup implementation.

You will just need to call the FollowScrollView() method. This class provides a ScrollingNavigationController property to help keep the code as clean as possible:

public override void ViewDidAppear (bool animated)
{
    base.ViewDidAppear (animated);

    if (ScrollingNavigationController != null) {
        // Enable the navbar scrolling
        ScrollingNavigationController.FollowScrollView (scrollView, 100.0);
    }
}

Instead of having to manage the StateChanged event, you can override the ScrollingNavigationStateChanged method:

public override void ScrollingNavigationStateChanged (NavigationBarState state)
{
    // handle the new state
}

To handle the scroll-to-top mechanism, you still need to attach the ShouldScrollToTop method to the scroll view. To perform custom logic when this happens, you can just override the ShouldScrollToTop method.

Write a Review

1 review

AnhNH rates this with
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This is great component! But i have found problem.

When i call NavigationController.PopToRoot, then scroll my TableView, Application will be crash :(. Anyone help me?

Posted on: December 14, 2015 / Version: 2.0.9.0