zeeshankhan

Hacking UIView animation blocks for fun and profit

In this article, I'm going to explore a way that we can create views that implement custom Core Animation property animations in a natural way.

As we know, layers in iOS come in two flavours: Backing layers and hosted layers. The only difference between them is that the view acts as the layer delegate for its backing layer, but not for any hosted sublayers.

In order to implement the UIView transactional animation blocks, UIView disables all animations by default and then re-enables them individually as required. It does this using the actionForLayer:forKey: method.

Somewhat strangely, UIView doesn't enable animations for every property that CALayer does by default. A notable example is the layer.contents property, which is animatable by default for a hosted layer, but cannot be animated using a UIView animation block.

zeeshankhan

import UIKit
import WebKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        
        // Configure the web view for JavaScript injection
        configureWebView()

zeeshankhan

// Original article here: https://www.fivestars.blog/code/swiftui-hierarchy-list.html

import SwiftUI

struct FileItem: Identifiable {
  let name: String
  var children: [FileItem]?

  var id: String { name }

zeeshankhan

import SwiftUI
import PlaygroundSupport

struct ContentView: View {
    @State var gradientAngle: Double = 0
    var colors = [
        Color(UIColor.systemRed),
        Color(UIColor.systemOrange),
        Color(UIColor.systemYellow),
        Color(UIColor.systemGreen),

zeeshankhan

// How to:
// 1. Go in the Firebase Analytics Dashboard
// 2. Filter iOS Platform only
// 3. Scroll down, select `Device` under the "What is your audience like?" widget
// 4. Export the CSV data (top right of the corner, there's a `...` menu with Download CSV option)
// 5. Open the file and select the iOS breakdown raw data
// 6. Replace your data with the sample data in this script
// 7. Run the script in a Xcode Playground
// 8. See the terminal output

zeeshankhan

// A Gist.
struct Gist {
    let id: String
}

typealias JSONDictionary = [String: AnyObject]

// These methods are "helpers" to transform Data -> JSON -> Result<[Gist]> 
func jsonFrom(data: Data) -> Result<AnyObject> {
    let json = try! JSONSerialization.jsonObject(with: data, options: [])