Customizable PullToRefresh

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

Requirements

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

Installing

with CocoaPods

use_frameworks!
pod 'PullToRefresher', '~> 3.1'

with Carthage

github "Yalantis/PullToRefresh"

Usage

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.removePullToRefresh(tableView.topPullToRefresh!)
}

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.

Usage in UITableView with sections

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

Create you own PullToRefresh (see instructions below).
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. ⚠️

Creating custom PullToRefresh

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)

Steps for creating custom PullToRefresh

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
}

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
    }
}

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.

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)
    }
}

Finally, add a refresher to a UIScrollView subclass:

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

Have fun! :)

Let us know!

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!

License

The MIT License (MIT)

Copyright © 2018 Yalantis

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.

dydus0x14/PullToRefresh