UIPageViewController with Peeking

I rewrite Kevin Jantzer answer in swift 4 and it's works!

override func viewDidLoad() {
    super.viewDidLoad()
    let pad: CGFloat = 20
    let items: [UIColor] = [.blue, .yellow, .red, .green]

    self.view.backgroundColor = .white

    var pageScrollView = UIScrollView(frame: self.view.frame)
    pageScrollView.isOpaque = false
    pageScrollView.showsHorizontalScrollIndicator = false
    pageScrollView.clipsToBounds = false
    pageScrollView.isPagingEnabled = true
    adjustFrame(myView: pageScrollView, x: pad, y: UIScreen.main.bounds.height / 4, w: -pad * 3, h: -UIScreen.main.bounds.height/2)

    self.view.addSubview(pageScrollView)
    let w = pageScrollView.frame.size.width

    for (i, item) in items.enumerated() {
        let myView = UIView(frame: pageScrollView.bounds)
        myView.backgroundColor = item
        setFrameX(myView: myView, x: (CGFloat(i) * w) + pad);
        setFrameW(myView: myView, w: w-(pad*1));
        pageScrollView.addSubview(myView)
    }

    pageScrollView.contentSize = CGSize(width: w * CGFloat(items.count), height: pageScrollView.frame.size.height);
}

func setFrame(myView: UIView, x: CGFloat?, y: CGFloat?, w: CGFloat?, h: CGFloat?){
    var f = myView.frame

    if let safeX = x {
        f.origin = CGPoint(x: safeX, y: f.origin.y)
    }
    if let safeY = y {
        f.origin = CGPoint(x: f.origin.x, y: safeY)
    }
    if let safeW = w {
        f.size.width = safeW
    }
    if let safeH = h {
        f.size.height = safeH
    }

    myView.frame = f
}

func setFrameX(myView: UIView, x: CGFloat) {
    setFrame(myView: myView, x: x, y: nil, w: nil, h: nil)
}
func setFrameY(myView: UIView, y: CGFloat) {
    setFrame(myView: myView, x: nil, y: y, w: nil, h: nil)
}
func setFrameW(myView: UIView, w: CGFloat) {
    setFrame(myView: myView, x: nil, y: nil, w: w, h: nil)
}
func setFrameH(myView: UIView, h: CGFloat) {
    setFrame(myView: myView, x: nil, y: nil, w: nil, h: h)
}

func adjustFrame(f: CGRect, x: CGFloat?, y: CGFloat?, w: CGFloat?, h: CGFloat?) -> CGRect {
    var rect = f

    if let safeX = x {
        rect.origin = CGPoint(x: rect.origin.x + safeX, y: f.origin.y)
    }
    if let safeY = y {
        rect.origin = CGPoint(x: f.origin.x, y: rect.origin.y + safeY)
    }
    if let safeW = w {
        rect.size.width = safeW + rect.size.width
    }
    if let safeH = h {
        rect.size.height = safeH + rect.size.height
    }

    return rect
}

func adjustFrame(myView: UIView, x: CGFloat, y: CGFloat, w: CGFloat, h: CGFloat) {
    myView.frame = adjustFrame(f: myView.frame, x: x, y: y, w: w, h: h);
}
}

Like @davew said, peeking views will need to use UIScrollView. I too searched for a way to use UIPageViewController but couldn't find any resource.

Using UIScrollView to make this feature was less painful that I had imagined.

---

Here is a simple example to see the basic controls in action.

First: make a UIViewController, then in the viewDidLoad method, add the following code:

float pad = 20;
NSArray* items = @[@"One", @"Two", @"Three", @"Four"];

self.view.backgroundColor = [UIColor greenColor];

UIScrollView* pageScrollView = [[UIScrollView alloc] initWithFrame:self.view.frame];
pageScrollView.opaque = NO;
pageScrollView.showsHorizontalScrollIndicator = NO;
pageScrollView.clipsToBounds = NO;
pageScrollView.pagingEnabled = YES;

adjustFrame(pageScrollView, pad, deviceH()/4, -pad*3, -deviceH()/2);

[self.view addSubview: pageScrollView];

float w = pageScrollView.frame.size.width;

for(int i = 0; i < [items count]; i++){
    UIView* view = [[UIView alloc] initWithFrame:pageScrollView.bounds];
    view.backgroundColor = [UIColor blueColor];
    setFrameX(view, (i*w)+pad);
    setFrameW(view, w-(pad*1));
    [pageScrollView addSubview:view];
}

pageScrollView.contentSize = CGSizeMake(w*[items count], pageScrollView.frame.size.height);

FYI, I used these util functions to adjust the size of the view frames; I get sick of manually changing them with 3+ lines of code.

Update

I have wrapped up this code in a simple ViewController and put it on GitHub

https://github.com/kjantzer/peek-page-view-controller

It is in no way complete, but it's a working start.

I was just searching for a good solution to the same feature. I found a nice tutorial on Ray Wenderlich's site titled "How To Use UIScrollView to Scroll and Zoom Content". It illustrates multiple things you can do with UIScrollView. The fourth and final is "Viewing Previous/Next Pages" which is your "peek" feature.

I haven't implemented this yet, but the key steps seem to be:

• Create a UIScrollView narrower than your screen
• Turn on Paging Enabled
• Turn off Clip Subviews
• Fill the UIScrollView with your pages side by side
• Embed the UIScrollView inside a UIView that fills the width of the screen so that you can capture and pass touches outside the Scroll View