85 lines
3.4 KiB
Swift
85 lines
3.4 KiB
Swift
//
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// SelfSizingCollectionView.swift
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// VDS
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//
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// Created by Matt Bruce on 11/18/22.
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//
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import Foundation
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import UIKit
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/// UICollectionView subclassed to deal with Changing the size of itself based on its children and layout and changes of its contentSize.
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@objc(VDSSelfSizingCollectionView)
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public final class SelfSizingCollectionView: UICollectionView {
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//--------------------------------------------------
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// MARK: - Initialization
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//--------------------------------------------------
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/// Initializer
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/// - Parameters:
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/// - frame: Frame needed
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/// - layout: Layout used for this CollectionView
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public override init(frame: CGRect, collectionViewLayout layout: UICollectionViewLayout) {
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super.init(frame: frame, collectionViewLayout: layout)
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self.setupContentSizeObservation()
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}
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public required init?(coder: NSCoder) {
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super.init(coder: coder)
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self.setupContentSizeObservation()
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}
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//--------------------------------------------------
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// MARK: - Private Properties
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//--------------------------------------------------
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private var contentSizeObservation: NSKeyValueObservation?
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//--------------------------------------------------
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// MARK: - Overrides
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//--------------------------------------------------
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/// The natural size for the receiving view, considering only properties of the view itself.
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public override var intrinsicContentSize: CGSize {
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let contentSize = self.contentSize
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//print(#function, contentSize)
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return CGSize(width: UIView.noIntrinsicMetric, height: contentSize.height)
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}
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/// Overridden to deal with Appearance Changes
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public override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
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//print(type(of: self), #function)
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super.traitCollectionDidChange(previousTraitCollection)
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// We need to handle any change that will affect layout and/or anything that affects size of a UILabel
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if self.traitCollection.hasDifferentTextAppearance(comparedTo: previousTraitCollection) {
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self.collectionViewLayout.invalidateLayout()
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}
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}
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//--------------------------------------------------
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// MARK: - Private Methods
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//--------------------------------------------------
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private func setupContentSizeObservation() {
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// Observing the value of contentSize seems to be the only reliable way to get the contentSize after the collection view lays out its subviews.
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self.contentSizeObservation = self.observe(\.contentSize, options: [.old, .new]) { [weak self] _, change in
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// If we don't specify `options: [.old, .new]`, the change.oldValue and .newValue will always be `nil`.
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if change.newValue != change.oldValue {
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self?.invalidateIntrinsicContentSize()
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}
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}
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}
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}
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extension UITraitCollection {
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/// Used within SelfSizingCollectionView to determine if there is an appearance change.
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/// - Parameter traitCollection: TraitCollection to compare.
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/// - Returns: True/False based on the trailCollection passed in.
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public func hasDifferentTextAppearance(comparedTo traitCollection: UITraitCollection?) -> Bool {
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var result = self.preferredContentSizeCategory != traitCollection?.preferredContentSizeCategory
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result = result || self.legibilityWeight != traitCollection?.legibilityWeight
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return result
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}
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}
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