metatext/Views/UIKit/Content Views/LoadMoreView.swift

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Swift
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// Copyright © 2020 Metabolist. All rights reserved.
import Combine
import UIKit
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final class LoadMoreView: UIView {
private let leadingArrowImageView = UIImageView()
private let trailingArrowImageView = UIImageView()
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private let label = UILabel()
private let activityIndicatorView = UIActivityIndicatorView()
private var loadMoreConfiguration: LoadMoreContentConfiguration
private var loadingCancellable: AnyCancellable?
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private var directionChange = LoadMoreView.directionChangeMax
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init(configuration: LoadMoreContentConfiguration) {
self.loadMoreConfiguration = configuration
super.init(frame: .zero)
initialSetup()
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applyLoadMoreConfiguration()
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}
@available(*, unavailable)
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
}
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extension LoadMoreView {
static let accessibilityCustomAction =
Notification.Name("com.metabolist.metatext.load-more-view.accessibility-custom-action")
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static var estimatedHeight: CGFloat {
.defaultSpacing * 2 + UIFont.preferredFont(forTextStyle: .title2).lineHeight
}
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func directionChanged(up: Bool) {
guard !loadMoreConfiguration.viewModel.loading else { return }
if up, directionChange < Self.directionChangeMax {
directionChange += Self.directionChangeIncrement
} else if !up, directionChange > -Self.directionChangeMax {
directionChange -= Self.directionChangeIncrement
}
updateDirectionChange(animated: false)
}
func finalizeDirectionChange() {
directionChange = directionChange > 0 ? Self.directionChangeMax : -Self.directionChangeMax
updateDirectionChange(animated: true)
}
}
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extension LoadMoreView: UIContentView {
var configuration: UIContentConfiguration {
get { loadMoreConfiguration }
set {
guard let loadMoreConfiguration = newValue as? LoadMoreContentConfiguration else { return }
self.loadMoreConfiguration = loadMoreConfiguration
applyLoadMoreConfiguration()
}
}
}
private extension LoadMoreView {
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static let directionChangeMax = CGFloat.pi
static let directionChangeIncrement = CGFloat.pi / 10
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// swiftlint:disable:next function_body_length
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func initialSetup() {
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for arrowImageView in [leadingArrowImageView, trailingArrowImageView] {
addSubview(arrowImageView)
arrowImageView.translatesAutoresizingMaskIntoConstraints = false
arrowImageView.image = UIImage(
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systemName: "arrow.up",
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withConfiguration: UIImage.SymbolConfiguration(
pointSize: UIFont.preferredFont(forTextStyle: .title2).pointSize))
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arrowImageView.contentMode = .scaleAspectFit
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arrowImageView.setContentHuggingPriority(.required, for: .horizontal)
}
addSubview(label)
label.translatesAutoresizingMaskIntoConstraints = false
label.textAlignment = .center
label.font = .preferredFont(forTextStyle: .title2)
label.adjustsFontForContentSizeCategory = true
label.textColor = label.tintColor
label.text = NSLocalizedString("load-more", comment: "")
label.setContentHuggingPriority(.defaultLow, for: .horizontal)
addSubview(activityIndicatorView)
activityIndicatorView.translatesAutoresizingMaskIntoConstraints = false
activityIndicatorView.hidesWhenStopped = true
NSLayoutConstraint.activate([
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heightAnchor.constraint(greaterThanOrEqualToConstant: .minimumButtonDimension * 2),
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leadingArrowImageView.leadingAnchor.constraint(equalTo: readableContentGuide.leadingAnchor),
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leadingArrowImageView.topAnchor.constraint(greaterThanOrEqualTo: readableContentGuide.topAnchor),
leadingArrowImageView.bottomAnchor.constraint(greaterThanOrEqualTo: readableContentGuide.bottomAnchor),
leadingArrowImageView.centerYAnchor.constraint(equalTo: centerYAnchor),
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label.leadingAnchor.constraint(equalTo: leadingArrowImageView.trailingAnchor),
label.topAnchor.constraint(greaterThanOrEqualTo: readableContentGuide.topAnchor),
label.bottomAnchor.constraint(greaterThanOrEqualTo: readableContentGuide.bottomAnchor),
label.trailingAnchor.constraint(equalTo: trailingArrowImageView.leadingAnchor),
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label.centerYAnchor.constraint(equalTo: centerYAnchor),
trailingArrowImageView.topAnchor.constraint(greaterThanOrEqualTo: readableContentGuide.topAnchor),
trailingArrowImageView.bottomAnchor.constraint(greaterThanOrEqualTo: readableContentGuide.bottomAnchor),
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trailingArrowImageView.trailingAnchor.constraint(equalTo: readableContentGuide.trailingAnchor),
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trailingArrowImageView.centerYAnchor.constraint(equalTo: centerYAnchor),
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activityIndicatorView.centerXAnchor.constraint(equalTo: centerXAnchor),
activityIndicatorView.centerYAnchor.constraint(equalTo: centerYAnchor)
])
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isAccessibilityElement = true
accessibilityLabel = NSLocalizedString("load-more", comment: "")
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let aboveAccessibilityActionName: String
let belowAccessibilityActionName: String
switch loadMoreConfiguration.viewModel.identityContext.appPreferences.statusWord {
case .toot:
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aboveAccessibilityActionName = NSLocalizedString("load-more.above.accessibility.toot", comment: "")
belowAccessibilityActionName = NSLocalizedString("load-more.below.accessibility.toot", comment: "")
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case .post:
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aboveAccessibilityActionName = NSLocalizedString("load-more.above.accessibility.post", comment: "")
belowAccessibilityActionName = NSLocalizedString("load-more.below.accessibility.post", comment: "")
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}
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accessibilityCustomActions = [
UIAccessibilityCustomAction(
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name: aboveAccessibilityActionName) { [weak self] _ in
self?.directionChange = -Self.directionChangeMax
self?.updateDirectionChange(animated: false)
NotificationCenter.default.post(name: Self.accessibilityCustomAction, object: self)
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return true
},
UIAccessibilityCustomAction(
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name: belowAccessibilityActionName) { [weak self] _ in
self?.directionChange = Self.directionChangeMax
self?.updateDirectionChange(animated: false)
NotificationCenter.default.post(name: Self.accessibilityCustomAction, object: self)
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return true
}
]
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}
func applyLoadMoreConfiguration() {
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loadingCancellable = loadMoreConfiguration.viewModel.$loading.sink { [weak self] in
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guard let self = self else { return }
self.label.isHidden = $0
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if $0 {
self.activityIndicatorView.startAnimating()
} else {
self.activityIndicatorView.stopAnimating()
}
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}
}
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func updateDirectionChange(animated: Bool) {
if animated {
UIView.animate(withDuration: 0.1) {
self.performDirectionChangeUpdates()
}
} else {
self.performDirectionChangeUpdates()
}
}
func performDirectionChangeUpdates() {
loadMoreConfiguration.viewModel.direction = directionChange > 0 ? .up : .down
leadingArrowImageView.transform = CGAffineTransform(rotationAngle: .pi / 2 - directionChange / 2)
trailingArrowImageView.transform = CGAffineTransform(rotationAngle: -.pi / 2 + directionChange / 2)
}
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}