Embedding container view into UIScrollView

Question

I've been searching high and low to try and figure this out hopefully someone can help (I think this is probably fairly trivial but I'm just over confusing the situation!)

I'm using XCode 5 and storyboards. I have a container view which takes up around 75% of the screen space on an iPhone. Above this I have some buttons (and other widgets). I want to be able to load in a view controller into the container when pushing one of the buttons.

So far all of this works ok, but the view controllers that are being loaded in are of different sizes, and could change in future. I would like to be able to allow the child view (of arbitrary size) to scroll.

I've tried embedding the container in a scroll view, but then as part of the process of add the new child view, you have to set the frame size, but I want the child to figure out how big it should be and then set everything accordingly.

I'm not entirely sure what the best way to go about this is (either setting constraints in the story board, or programmatically?)

Any advice would be great! Or a link to a tutorial would be very useful, the only ones I could find were for adding view controllers to a container view or adding views to a scroll view, none of which seem to work quite as expected with Xcode 5 (iOS 7)

Thanks!

-Edit-

Here's the code I used to present a detail view controller of arbitrary size, the rest was all set in the storyboard (just in case this is useful to anyone in future!) This now works:

- (void)presentDetailController:(UIViewController*)detailVC{

//0. Remove the current Detail View Controller shown
if(self.currentDetailViewController){
    [self removeCurrentDetailViewController];
}

//1. Add the detail controller as child of the container
[self addChildViewController:detailVC];

//2. DO NOT Define the detail controller's view size
//detailVC.view.frame = [self frameForDetailController];

//3. Add the Detail controller's view to the Container's detail view and save a reference to the detail View Controller
[self.detailView addSubview:detailVC.view];
self.currentDetailViewController = detailVC;

// Pin the height to the container to make it scrollable?
[self.detailView addConstraint:[NSLayoutConstraint constraintWithItem:self.detailView attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeHeight multiplier:1.0f constant:detailVC.view.bounds.size.height]];

//4. Complete the add flow calling the function didMoveToParentViewController
[detailVC didMoveToParentViewController:self];

}

Answer 1

You can set constraints in either place and have it work correctly. The secret is this: you must set your container view's constraints to the top, left, bottom, and right of the scroll view that contains it. Autolayout will then calculate the scroll view's content size correctly based on what is inside of the container view.

See the section titled Pure Auto Layout Approach in the iOS 6 release notes. There's even some example code.

// parentView is the thing you want to add the scroll view to


// setup the scroll view, and add it to the parent view
UIScrollView* scrollView = [[UIScrollView alloc] init];
scrollView.backgroundColor = [UIColor colorWithWhite:0.9f alpha:1.0f];

[parentView addSubview:scrollView];

scrollView.translatesAutoresizingMaskIntoConstraints = NO;

NSDictionary* views = NSDictionaryOfVariableBindings(scrollView);

[parentView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[scrollView]|" options:0 metrics:nil views:views]];
[parentView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[scrollView]|" options:0 metrics:nil views:views]];


// set up the content
UILabel* firstLongLabel = [[UILabel alloc] init];
firstLongLabel.numberOfLines = 0;
firstLongLabel.text = @" Four score and seven years ago our fathers brought forth, on this continent, a new nation, conceived in Liberty, and dedicated to the proposition that all men are created equal.\n\nNow we are engaged in a great civil war, testing whether that nation, or any nation so conceived, and so dedicated, can long endure. We are met on a great battle-field of that war. We have come to dedicate a portion of that field, as a final resting-place for those who here gave their lives, that that nation might live. It is altogether fitting and proper that we should do this.";
firstLongLabel.backgroundColor = [UIColor greenColor];

UIButton* middleButton = [UIButton buttonWithType:UIButtonTypeSystem];
[middleButton setTitle:@"Middle Button" forState:UIControlStateNormal];
middleButton.backgroundColor = [UIColor purpleColor];

UILabel* lastLongLabel = [[UILabel alloc] init];
lastLongLabel.numberOfLines = 0;
lastLongLabel.text = @"But, in a larger sense, we can not dedicate, we can not consecrate – we can not hallow – this ground. The brave men, living and dead, who struggled here, have consecrated it far above our poor power to add or detract. The world will little note, nor long remember what we say here, but it can never forget what they did here. It is for us the living, rather, to be dedicated here to the unfinished work which they who fought here have thus far so nobly advanced. It is rather for us to be here dedicated to the great task remaining before us – that from these honored dead we take increased devotion to that cause for which they here gave the last full measure of devotion - that we here highly resolve that these dead shall not have died in vain – that this nation, under God, shall have a new birth of freedom, and that government of the people, by the people, for the people, shall not perish from the earth.";
lastLongLabel.backgroundColor = [UIColor yellowColor];


// now create a content view and add all of our previously created content to it
UIView* contentView = [[UIView alloc] init];
contentView.backgroundColor = [UIColor blueColor];

[contentView addSubview:firstLongLabel];
[contentView addSubview:middleButton];
[contentView addSubview:lastLongLabel];

[scrollView addSubview:contentView];


// and now comes the important part.. the constraints
firstLongLabel.translatesAutoresizingMaskIntoConstraints = middleButton.translatesAutoresizingMaskIntoConstraints = lastLongLabel.translatesAutoresizingMaskIntoConstraints = contentView.translatesAutoresizingMaskIntoConstraints = NO;

views = NSDictionaryOfVariableBindings(firstLongLabel, middleButton, lastLongLabel, contentView);

// first, add constraints dealing with the content inside the content view
// these are simple and should be easily understood
[contentView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-10-[firstLongLabel]-10-|" options:0 metrics:nil views:views]];
[contentView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-10-[middleButton]-10-|" options:0 metrics:nil views:views]];
[contentView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-10-[lastLongLabel]-10-|" options:0 metrics:nil views:views]];

[contentView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-10-[firstLongLabel]-10-[middleButton]-10-[lastLongLabel]-10-|" options:0 metrics:nil views:views]];

// then add constraints dealing with the content view that we put into the scroll view...
// the trick here is that we lock the content to only partially the width
// of the scroll view's parent. if we don't do that, then the labels will force the scroll
// view to expand horizontally instead of vertically.
//
// as an exercise, you can try locking the left and right to the scroll view instead of the parent view to see what happens
[parentView addConstraint:[NSLayoutConstraint constraintWithItem:contentView attribute:NSLayoutAttributeLeft relatedBy:NSLayoutRelationEqual toItem:parentView attribute:NSLayoutAttributeLeft multiplier:1 constant:10]];
[parentView addConstraint:[NSLayoutConstraint constraintWithItem:contentView attribute:NSLayoutAttributeRight relatedBy:NSLayoutRelationEqual toItem:parentView attribute:NSLayoutAttributeRight multiplier:1 constant:-10]];

// by locking the content view's vertical edges to that of the scroll view, it'll cause the
// scroll view to expand vertically to accomodate the entire content view
[scrollView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-10-[contentView]-10-|" options:0 metrics:nil views:views]];