What is the extend edge property in UIViewController for ? - ios

I have read on the forums about this property, mostly its people setting this this property to false or unchecking it in the storyboard.
I have done this myself because when I have a UINavigation Controller embedded in a View, the top bar pushes my UITextView down so the text starts editing at the bottom.
Unchecking Extended Edges Under Top Bars in the StoryBoard in the UIViewController solves my problem but I don't understand what is going on.
Can someone give an explanation on what the purpose of this property is, I would like to know more about it.

By default, UITableViewController's views are automatically inset in iOS7 so that they don't start below the navigation bar/status bar. This is controller by the "Adjust scroll view insets" setting on the Attributes Inspector tab of the UITableViewController in Interface Builder, or by the setAutomaticallyAdjustsScrollViewInsets: method of UIViewController.
For a UIViewController's contents, if you don't want its view's contents to extend under the top/bottom bars, you can use the Extend Edges Under Top Bars/Under Bottom Bars settings in Interface Builder. This is accessible via the edgesForExtendedLayout property.
Reference: Why does UIViewController extend under UINavigationBar, while UITableViewController doesn't?

See the images below:
I set 44 height red topview and 44 height red footview of tableview.
UIRectEdgeTop: The top edge of the rectangle.
UIRectEdgeBottom: The bottom edge of the rectangle.

The edgesForExtendedLayout property, together with the extendedLayoutIncludesOpaqueBars property, determines whether or not view controllers' views underlap top and bottom bars (navigation bar, toolbar, etc.)

Related

UIView Under Nav and Tab Bars

Using storyboard and Swift, I have a view controller which has two elements on it. A UITextField, and a UIView, which I use merely to give a colored border to the UITextField. The UITextField is a child of the UIView. See:
The problem I am having is that despite having set the top bar and bottom bar simulated metrics attributes to Opaque Navigation Bar and Opaque Tab Bar respectively, See:
When the app builds and runs the top of the UIView is always underneath the nav bar. My over all feeling is that this is somehow a constraints issue but I have not been able to find the solution to it. How do I set the constraints so that the UIView is always immediately underneath the nav bar, and the bottom of the view is always just on top of the tab bar?
Select your UIView in storyboard and assign constraints to the top margins and to bottom margins. There is a 'Pin' button you use to do this that looks something like a Tie-Fighter ship in Star Wars, it is located at the bottom right of your storyboard view.
This will set margins to stretch to top and bottom always.
That is what the layout guides are for. Pin the top to the Top Layout Guide and the bottom to the Bottom Layout Guide. The guides will always move to adjust for any top and bottom bars.

UITableViewController Inside UINavigationController and UITabBarController Bottom Inset Off

I have a UITableView inside a UINavigationController that's inside a UITabBarController. There is a view on the bottom (I'll call it bottomView) between the table view and the tab bar that needs to stay at the bottom as the table view scrolls, so I can't put it as a footer in the table view.
The issue is that when i scroll to the bottom of the table view, there is an empty space the same height as the tab bar between the lowest content (and the scroll bar) and the top of bottomView.
I think this is because the table view is trying to automatically compensate for the tab view at the bottom, but I can't position it all the way at the bottom because of bottomView.
here's my IB layout:
and the display (last tableViewCell highlighted):
If I understand your question correct you need to set a contentInset to your tableView like this:
[self.tableView setContentInset:UIEdgeInsetsMake(0,0,44,0)];
Edit:
Ok I think I got it. Set:
self.automaticallyAdjustsScrollViewInsets=NO;
I've seen this same nav controller->tab bar->tableview situation frustratingly cause the tableview to partially overlap with the navigation bar, instead of not reaching the tab bar. To anyone having this issue when using a UITableView: ensure your navigation bar is not translucent. If you want to use this setup with a translucent navigation bar, select the UITabBarController in the Interface Builder and uncheck the "extend edges under top bars" option in the attributes inspector.

UITableView Current section floating not where it should

An image is worth a 1000 words, so here is a screen :
As you can see, the "A" section is the current section and there is space above it and I can't understand why.
FWIW : It's a UISearchResultsTableView (UITableView subclass) create by a UISearchDisplayController.
This problem appear I think after some changed in the interface builder but I can't find what exactly.
It look likes it the space is the same height as the navigationbar.
By default, UITableViewController's views are automatically inset in iOS 7 so that they don't start below the navigation bar/status bar.
This is controller by the Adjust scroll view insets setting on the Attributes Inspector tab of the UITableViewController in Interface Builder, or by the setAutomaticallyAdjustsScrollViewInsets: method of UIViewController.
For a UIViewController's contents, if you don't want its view's contents to extend under the top/bottom bars, you can use the Extend Edges Under Top Bars/Under Bottom Bars settings in Interface Builder. This is accessible via the edgesForExtendedLayout property.
Try:
self.edgesForExtendedLayout = UIRectEdgeNone;
self.automaticallyAdjustsScrollViewInsets = NO;

Autolayout adding extra padding

I have a UITableViewController in a Storyboard that I'm adding as a subview to a lone UIView in a UIViewController, my end goal is to get the UITableView flush up against the status bar so that scrolling goes underneath the status bar (not through it with clashes).
I have configured the lone UIView to have constraints of 0 on both verticals and horizontals but as demonstrated in the image I believe autolayout is then adding the 20px y offset that I am including in the layout. If I remove the 20px y offset (and size the UIView to the whole layout) I end up with the clashing.
I suggest you to set up your view controller as follows. Create a UIViewController in IB and add a simple UITableView as a subview of its main view. I almost never use the UITableViewController because it has almost no added value but it restricts you in adding subviews to your table view. Now, you position your table view's origin to (0, 20) and set up the top layout constraint of the table view to the top layout guide instead of the superview. Maybe you should open the drop down menu close to the constraint constant value in IB:
This way your table view will start right under the status bar.
Note however that iOS 7 design guidelines suggest that you would in fact extend the content under the top bars (nav bar and status bar). You should create a 20 points high semi-transparent background png, position it under the status bar, and leave the table view to scroll under the status bar. In this case you should also not forget to check in the "Adjust scroll views inset" option of your view controller.

How to make a UITableViewController subclass respect topLayoutGuide in iOS7?

in my app I have a simple UITableViewController that's just plain Objective-C code, no .xib or storyboard involved. It represents the contents of one tab in a tab bar.
Since iOS 7 its contents are overlapped by the status bar at the top and tab bar at the bottom.
Using only code, how can I make the table view add space at the top and bottom to align with topLayoutGuide and bottomLayoutGuide?
I know about
self.edgesForExtendedLayout=UIRectEdgeNone;
but that seems to simply shrink the table view to not intersect the tab bar and to disable the transparency of the tab bar. Instead I'd like the table view to add some padding.
Thanks!
Update:
I've also tried explicitly setting automaticallyAdjustsScrollViewInsets to YES, but that didn't help either (should be the default behavior anyway).
It seems this is not (yet) supported, at least for programmatically created UITableViewControllers without an UINavigationController that's embedding them.
I checked the position for both layout guides, and at run-time both off-sets read 0 distance from the edges of the screen. Hence automaticallyAdjustsScrollViewInsets won't set the insets correctly.
So now I actually modify my first section header and last section footer manually to add 21 pixels at the top and 50 pixels at the bottom respectively.
Bummer. :-(

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