collection中cell选中状态下分享图片的快照snapshot

总结要点

注意:
1:shouldPerformSegue(withIdentifier:sender:) -> bool 方法控制segue的效能
2: let index = selectedIcons.index(where:{$0.icon.name == deSelectedIcon.name})
index(where)条件返回index
3:snapshot生成快照
UIGraphicsBeginImageContext(bounds.size)
if let context = UIGraphicsGetCurrentContext(){
self.layer.render(in:context)
image = UIGraphicsGetImageFromCurrentImageContext()
}
UIGraphicsEndImageContext()
return image
4:let indexPaths = collectionView.indexPathsForSelectedItems返回多个索引,所以在单选的情况下,通过indexPaths.first来获取
5:prepare(for:sender:) 与 shouldPerformSegue(withIdentifier identifier: String, sender: Any?) -> Bool连用
6:@IBAction func unwindToHome(segue:UIStoryboardSegue){}//退出exit时link的方法(解除segue)

IconCollectionViewController.swift
IconDetailViewController.swift
IconCollectionViewCell.swift
Icon.swift
UIView+Snapshot.swift

IconCollectionViewController.swift

import UIKitprivate let reuseIdentifier = "Cell"class IconCollectionViewController: UICollectionViewController {private var iconSet: [Icon] = [ Icon(name: "Candle icon", imageName: "candle", description: "Halloween icons designed by Tania Raskalova.", price: 3.99, isFeatured: false),Icon(name: "Cat icon", imageName: "cat", description: "Halloween icon designed by Tania Raskalova.", price: 2.99, isFeatured: true),Icon(name: "dribbble", imageName: "dribbble", description: "Halloween icon designed by Tania Raskalova.", price: 1.99, isFeatured: false),Icon(name: "Ghost icon", imageName: "ghost", description: "Halloween icon designed by Tania Raskalova.", price: 4.99, isFeatured: false),Icon(name: "Hat icon", imageName: "hat", description: "Halloween icon designed by Tania Raskalova.", price: 2.99, isFeatured: false),Icon(name: "Owl icon", imageName: "owl", description: "Halloween icon designed by Tania Raskalova.", price: 5.99, isFeatured: true),Icon(name: "Pot icon", imageName: "pot", description: "Halloween icon designed by Tania Raskalova.", price: 1.99, isFeatured: false),Icon(name: "Pumkin icon", imageName: "pumkin", description: "Halloween icon designed by Tania Raskalova.", price: 0.99, isFeatured: false),Icon(name: "RIP icon", imageName: "rip", description: "Halloween icon designed by Tania Raskalova.", price: 7.99, isFeatured: false),Icon(name: "Skull icon", imageName: "skull", description: "Halloween icon designed by Tania Raskalova.", price: 8.99, isFeatured: false),Icon(name: "Sky icon", imageName: "sky", description: "Halloween icon designed by Tania Raskalova.", price: 0.99, isFeatured: false),Icon(name: "Toxic icon", imageName: "toxic", description: "Halloween icon designed by Tania Raskalova.", price: 2.99, isFeatured: false),Icon(name: "Book icon", imageName: "ic_book", description: "Colorful icon designed by Marin Begović.", price: 2.99, isFeatured: false),Icon(name: "Backpack icon", imageName: "ic_backpack", description: "Colorful icon designed by Marin Begović.", price: 3.99, isFeatured: false),Icon(name: "Camera icon", imageName: "ic_camera", description: "Colorful camera icon designed by Marin Begović.", price: 4.99, isFeatured: false),Icon(name: "Coffee icon", imageName: "ic_coffee", description: "Colorful icon designed by Marin Begović.", price: 3.99, isFeatured: true),Icon(name: "Glasses icon", imageName: "ic_glasses", description: "Colorful icon designed by Marin Begović.", price: 3.99, isFeatured: false),Icon(name: "Icecream icon", imageName: "ic_ice_cream", description: "Colorful icon designed by Marin Begović.", price: 4.99, isFeatured: false),Icon(name: "Smoking pipe icon", imageName: "ic_smoking_pipe", description: "Colorful icon designed by Marin Begović.", price: 6.99, isFeatured: false),Icon(name: "Vespa icon", imageName: "ic_vespa", description: "Colorful icon designed by Marin Begović.", price: 9.99, isFeatured: false)]@IBOutlet weak var shareButton: UIBarButtonItem!fileprivate var shareEnabled = falsefileprivate var selectedIcons:[(icon:Icon,snapshot:UIImage)] = []override func viewDidLoad() {super.viewDidLoad()}@IBAction func shareButtonTapped(_ sender: Any) {guard shareEnabled else {// 变更shareEnabled为YES并变更按钮文字为DoneshareEnabled = truecollectionView?.allowsMultipleSelection = trueshareButton.title = "Done"shareButton.style = UIBarButtonItemStyle.donereturn}// 确认是使用者至少有选择一个图片guard selectedIcons.count > 0  else {let alet = UIAlertController(title: "注意", message: "请选择分享的图片", preferredStyle: .alert)self.present(alet, animated: true) {alet.dismiss(animated: true, completion: nil)}return}// 取得所选图片的快照let snapshots = selectedIcons.map { $0.snapshot}// 建立分享用的动态视图控制器let activityController = UIActivityViewController(activityItems: snapshots, applicationActivities: nil)///typedef void (^UIActivityViewControllerCompletionWithItemsHandler)(UIActivityType activityType, BOOL completed, NSArray *returnedItems, NSError *activityError);activityController.completionWithItemsHandler = {(activityType, completed, returnedItems, activityError) in// 取消所有选取项目if let indexPaths = self.collectionView?.indexPathsForSelectedItems {for indexPath in indexPaths {self.collectionView?.deselectItem(at: indexPath, animated: false)}}// selectedIcons阵列中移除所有项目self.selectedIcons.removeAll(keepingCapacity: true)// 变更分享模式为NOself.shareEnabled = falseself.collectionView?.allowsMultipleSelection = falseself.shareButton.title = "Share"self.shareButton.style = UIBarButtonItemStyle.plain}present(activityController, animated: true, completion: nil)}/*很重要,注意点 因为segue是在每一个cell被按下时会被调用,但当app在分享模式下,我们不要触发这个segue,只要在单选模式时才需要触发它,*/override func shouldPerformSegue(withIdentifier identifier: String, sender: Any?) -> Bool {if identifier == "showIconDetail"{if shareEnabled {return false}}return true}@IBAction func unwindToHome(segue:UIStoryboardSegue){}override func prepare(for segue: UIStoryboardSegue, sender: Any?) {if segue.identifier == "showIconDetail"{if let indexPaths = collectionView?.indexPathsForSelectedItems{let destinationController = segue.destination as! IconDetailViewControllerdestinationController.icon = iconSet[indexPaths[0].row]collectionView?.deselectItem(at: indexPaths[0], animated: false)}}}// MARK: UICollectionViewDelegateoverride func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {// 检查分享模式是否已经启动,没有的话就离开这个方法guard shareEnabled else {return}// 使用indexPath来判断所选的项目并带入一个快照let selectedIcon = iconSet[indexPath.row]if let snapshot = collectionView.cellForItem(at: indexPath)?.snapshot {// 增加选中的item到arrayselectedIcons.append((icon: selectedIcon, snapshot: snapshot))}}override func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath) {// 检查分享模式是否启动,没有的话就离开这个方法guard shareEnabled else {return}let deSelectedIcon = iconSet[indexPath.row]/* 找到所选图示的索引,这里我们使用索引方法并传递一个闭包.在闭包中我们对所选图示的名称与所选图示阵列的所有项目做比较,如果名称有符合的话,这个索引方法将会回传其索引值,用这个索引值移除这个item*/if let index = selectedIcons.index(where: {$0.icon.name == deSelectedIcon.name}){selectedIcons.remove(at: index)}}// MARK: UICollectionViewDataSourceoverride func numberOfSections(in collectionView: UICollectionView) -> Int {// Return the number of sectionsreturn 1}override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {// Return the number of itemsreturn iconSet.count}override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {let cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPath) as! IconCollectionViewCell// Configure the celllet icon = iconSet[indexPath.row]cell.iconImageView.image = UIImage(named: icon.imageName)cell.iconPriceLabel.text = "$\(icon.price)"cell.backgroundView = (icon.isFeatured) ? UIImageView(image: UIImage(named: "feature-bg")) : nilcell.selectedBackgroundView = UIImageView(image: UIImage(named: "icon-selected"))return cell}}

IconDetailViewController.swift

import UIKitclass IconDetailViewController: UIViewController {var icon:Icon?@IBOutlet weak var iconImageView: UIImageView!{didSet{iconImageView.image = UIImage(named: icon?.imageName ?? "")}}@IBOutlet weak var nameLabel: UILabel!{didSet{nameLabel.text = icon?.name}}@IBOutlet weak var descriptionLabel: UILabel!{didSet{descriptionLabel.text = icon?.descriptiondescriptionLabel.numberOfLines = 0}}@IBOutlet weak var priceLabel: UILabel!{didSet{if let icon = icon {priceLabel.text = "$\(icon.price)"}}}@IBAction func buyAction(_ sender: UIButton) {}
}

IconCollectionViewCell.swift

class IconCollectionViewCell: UICollectionViewCell {@IBOutlet var iconImageView: UIImageView!@IBOutlet var iconPriceLabel: UILabel!
}

Icon.swift

import Foundationstruct Icon {var name: String = ""var imageName = ""var description = ""var price: Double = 0.0var isFeatured: Bool = falseinit(name: String, imageName: String, description: String, price: Double, isFeatured: Bool) {self.name = nameself.imageName = imageNameself.description = descriptionself.price = priceself.isFeatured = isFeatured}
}

UIView+Snapshot.swift

import Foundation
import UIKitextension UIView {/*取得视图快照的方式:以视图的大小来建立一个点阵圆为主的图形内容(context),然后我们渲染(render)视图的Neri,并从中取得图片*/var snapshot : UIImage? {var image:UIImage? = nilUIGraphicsBeginImageContext(bounds.size)if let context = UIGraphicsGetCurrentContext(){self.layer.render(in: context)image = UIGraphicsGetImageFromCurrentImageContext()}UIGraphicsEndImageContext()return image}
}

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