# ScrollingFollowView

[![Platform](http://img.shields.io/badge/platform-ios-blue.svg?style=flat
)](https://developer.apple.com/iphone/index.action)
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)](https://developer.apple.com/swift)
<a href="https://github.com/Carthage/Carthage/"><img src="https://img.shields.io/badge/Carthage-compatible-4BC51D.svg?style=flat"></a>

ScrollingFollowView is a simple view which follows UIScrollView scrolling.

#### ScrollingFollowView Sample Images
- SearchBarSample    : SearchBar Area
- ProfileViewSample  : Like Profile View Area
- BottomButtonSample : SearchBar and Bottom Button Area

![](./SampleImage/SearchBarSample.gif)
![](./SampleImage/ProfileViewSample.gif)
![](./SampleImage/BottomButtonSample.gif)

## Installation
### CocoaPods
ScrollingFollowView is available through [CocoaPods](http://cocoapods.org). To install it simply add the following line to your Podfile:

```
pod "ScrollingFollowView"
```

Then you can import it with:

```
import ScrollingFollowView
```

### Carthage
ScrollingFollowView is available throught [Carthage](https://github.com/Carthage/Carthage). To install it simply add the following line to your Cartfile:

```
github "ktanaka117/ScrollingFollowView"
```

Run `carthage update` to build the framework and drag the built `ScrollingFollowView.framework` into your Xcode project.

Click below link if you would like to know more about using Carthage: https://github.com/Carthage/Carthage#if-youre-building-for-ios-tvos-or-watchos

## How to Use
### Layout InterfaceBuilder
ScrollingFollowView only supports Autolayout use. 
(I don't force this feature on library users. I'm going to modify this feature. Plz look Future Improvements.)
You must make layouts with InterfaceBuilder like under sample image.

![](./SampleImage/HowToUse.png)
![](./SampleImage/module.jpg)

### Code
```swift
@IBOutlet weak var scrollingFollowView: ScrollingFollowView!

// NSLayoutConstraint of moving edge.
@IBOutlet weak var constraint: NSLayoutConstraint!

override func viewDidLoad() {
    super.viewDidLoad()

    let scrollingFollowViewHeight = scrollingFollowView.frame.size.height
    let statusBarHeight = UIApplication.sharedApplication().statusBarFrame.size.height

    // First setup
    // In default use, maxFollowPoint should be maxPoint of following to scroll DOWN.
    // In default use, minFollowPoint should be maxPoint of following to scroll UP.
    scrollingFollowView.setup(constraint: constraint, maxFollowPoint: scrollingFollowViewHeight + statusBarHeight, minFollowPoint: 0)
}
```

```swift
func scrollViewDidScroll(scrollView: UIScrollView) {
	// scrollingFollowView follows UIScrollView scrolling.
    scrollingFollowView.didScroll(scrollView)
}
```

## Advanced Use
### Use show(animated:) and hide(animated:)
You can use `show(animated:)` and `hide(animated:)` methods to ScrollingFollowView object like these:

```swift
// show
@IBAction func showButton() {
	scrollingFollowView.show(true)
	scrollingFollowView.resetPreviousPoint(scrollView)
}
// hide
@IBAction func hideButton() {
	scrollingFollowView.hide(false)
	scrollingFollowView.resetPreviousPoint(scrollView)
}
```

`resetPreviousPoint(scrollView:)` must call after `show(animated:)` and `hide(animated)`, `previousPoint` is ScrollingFollowView's private property which used changing constraint.constant value.

And show and hide methods are declared as:
```swift
func show(animated: Bool, duration: Double = 0.2, completionHandler: (()->())? = nil)
func hide(animated: Bool, duration: Double = 0.2, completionHandler: (()->())? = nil)
```

so you can set `animation duration` and `completionHandler` which used after animation:

```swift
// show
@IBAction func showButton() {
	scrollingFollowView.show(true, duration: 0.6) { print("showed") }
	scrollingFollowView.resetPreviousPoint(scrollView)
}
// hide
@IBAction func hideButton() {
	scrollingFollowView.hide(true, duration: 0.5) { print("hid") }
	scrollingFollowView.resetPreviousPoint(scrollView)
}
```

### Use DelayPoints
You can use hide and show delay points like under gif:

![](./SampleImage/DelaySample.gif)

Add `setupDelayPoints(pointOfStartingHiding:pointOfStartingShowing:)`.
For example, write in `viewDidLoad()`:

```swift
override func viewDidLoad() {
    super.viewDidLoad()

    let scrollingFollowViewHeight = scrollingFollowView.frame.size.height
    let statusBarHeight = UIApplication.sharedApplication().statusBarFrame.size.height

    scrollingFollowView.setup(constraint: constraint, maxFollowPoint: scrollingFollowViewHeight + statusBarHeight, minFollowPoint: 0)

    scrollingFollowView.setupDelayPoints(pointOfStartingHiding: 100, pointOfStartingShowing: 50)
}
```

### Use Controlling Half-Display

You can control half-display state like under gif:

allowHalfDisplay

![](./SampleImage/allowHalfDisplay.gif)

disallowHalfDisplay(Auto Animation)

![](./SampleImage/disallowHalfDisplay.gif)

You have to add parameter `allowHalfDisplay` to `setup(constraint:maxFollowPoint:minFollowPoint:allowHalfDesplay:)` function.

```swift
override func viewDidLoad() {
    super.viewDidLoad()

    let scrollingFollowViewHeight = scrollingFollowView.frame.size.height
    let statusBarHeight = UIApplication.sharedApplication().statusBarFrame.size.height

    // allowHalfDisplay: Default is false.
    // When allowHalfDisplay is true, ScrollingFollowView can display following scrolling state.
    // When allowHalfDisplay is false, ScrollingFollowView can't display following scrolling state. (If ScrollingFollowView is half-display state, it automatically animates.)
    scrollingFollowView.setup(constraint: constraint, maxFollowPoint: scrollingFollowViewHeight + statusBarHeight, minFollowPoint: 0, allowHalfDisplay: true)
}
```

and you also have to call `didEndScrolling()` and `didEndScrolling(_ decelerate:)` at `scrollViewDidEndDecelerating(_ scrollView:)` and `scrollViewDidEndDragging(_ scrollView:willDecelerate:)`.

```swift
extension ViewController: UIScrollViewDelegate {
    func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
        navBarScrollingFollowView.didEndScrolling()
    }
    
    func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
        navBarScrollingFollowView.didEndScrolling(decelerate)
    }
}
```

## Runtime Requirements

- iOS 8.0 or later
- Swift 3.0 or later
- Xcode 8.0 or later

## Future Improvements
- Refactoring.💪
- Enable to use like UITabBarController.
- Enable to implement only using code.
- Enable to move ScrollingFollowView using frame layout.
- Enable to horizontally move ScrollingFollowView.
- Enable to manage constraint without passing constraint argument. (I think we only want to chose an edge which follows scrolling. Like .Top, .Bottom, .Left, .Right.)

## Contact
When you have some opinions or ideas about this library, send me a reply on Twitter.🍣
[@ktanaka117](https://twitter.com/ktanaka117)

## License
ScrollingFollowView is released under the MIT license. Go read the LICENSE file for more information.