This component implements pure pull-to-refresh logic and you can use it for developing your own pull-to-refresh animations, like this one.

• iOS 8.0+
• Swift 5.0 (v 3.2+)
• Swift 4.2 (v 3.1+)
• Swift 3 (v. 2.0+)
• Swift 2 (v. 1.4)

use_frameworks!
pod 'PullToRefresher'

github "Yalantis/PullToRefresh"

At first, import PullToRefresh:

import PullToRefresh

The easiest way to create PullToRefresh:

let refresher = PullToRefresh()

It will create a default pull-to-refresh with a simple view which has single UIActivitiIndicatorView. To add refresher to your UIScrollView subclass:

tableView.addPullToRefresh(refresher) {
    // action to be performed (pull data from some source)
}

⚠️ Don't forget to remove pull to refresh when your view controller is releasing. ⚠️

deinit {
    tableView.removeAllPullToRefresh()
}

After the action is completed and you want to hide the refresher:

tableView.endRefreshing()

You can also start refreshing programmatically:

tableView.startRefreshing()

But you probably won’t use this component, though. UITableViewController and UICollectionViewController already have a simple type of refresher. It’s much more interesting to develop your own pull-to-refresh control.

Unfortunaly, UITableView with sections currently not supported. But you can resolve this problem in two steps:

1. Create you own PullToRefresh (see instructions below).
2. Set its shouldBeVisibleWhileScrolling property to true. It makes you PullToRefresh always visible while you're scrolling the table.

⚠️ By default PullToRefresh has transparent background which leads to unwanted overlapping behavour. ⚠️

You can disable/enable refresher in runtime:

yourRefresher.setEnable(isEnabled: false)

To create a custom refresher you would need to initialize PullToRefresh class with two objects:

• refreshView is a UIView object which will added to your scroll view;
• animator is an object which will animate elements on refreshView depending on the state of PullToRefresh.

let awesomeRefresher = PullToRefresh(refresherView: yourView, animator: yourAnimator)

1. Create a custom UIView with *.xib and add all images that you want to animate as subviews. Pin them with outlets:

class RefreshView: UIView {

    @IBOutlet private var imageView: UIImageView!
  
    // and others
}

2. Create an Animator object that conforms RefreshViewAnimator protocol and can be initialized by your custom view:

class Animator: RefreshViewAnimator {

    private let refreshView: RefreshView
    
    init(refreshView: RefreshView) {
        self.refreshView = refreshView
    }

    func animate(state: State) {
        // animate refreshView according to state
    }
}

3. According to RefreshViewAnimator protocol, your animator should implement animateState method. This method is get called by PullToRefresh object every time its state is changed. There are four states:

public enum State: Equatable, CustomStringConvertible {
    
    case initial
    case releasing(progress: CGFloat)
    case loading
    case finished
}

• Initial - refresher is ready to be pulled.
• Releasing - refresher is in the process of releasing (by a user or programmatically). This state contains a double value which represents releasing progress from 0 to 1.
• Loading - refresher is in the loading state.
• Finished - loading is finished.

Depending on the state that your animator gets from the PullToRefresh, it has to animate elements in refreshView:

func animate(state: State) {
    switch state {
      case .initial: // do inital layout for elements
      case .releasing(let progress): // animate elements according to progress
      case .loading: // start loading animations
      case .finished: // show some finished state if needed
    }
}

Place the magic of animations insted of commented lines.

4. For the convitience sake you can sublass from PullToRefresh and create separate class for your refresher:

class AwesomePullToRefresh: PullToRefresh {

    convenience init() {
        let refreshView = Bundle(for: type(of: self)).loadNibNamed("RefreshView", owner: nil, options: nil)!.first as! RefreshView
        let animator = Animator(refreshView: refreshView)
        self.init(refreshView: refreshView, animator: animator)
    }
}

5. Finally, add a refresher to a UIScrollView subclass:

tableView.addPullToRefresh(refresher) {
    // action to be performed (pull data from some source)
}

Have fun! :)

We’d be really happy if you sent us links to your projects where you use our component. Just send an email to github@yalantis.com And do let us know if you have any questions or suggestion regarding the animation.

P.S. We’re going to publish more awesomeness wrapped in code and a tutorial on how to make UI for iOS (Android) better than better. Stay tuned!

The MIT License (MIT)

Copyright © 2018 Yalantis

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