Photo selector collectionview

1. Definition PicturePickerController 

import UIKit
// reusable  Cell
private let PicturePickerCellId = "PicturePickerCellId"
// Maximum number of selected photos 
private let PicturePickerMaxCount = 8
//MARK: -  Photo picker 
class PicturePickerController: UICollectionViewController {
    
    // Matching array 
    lazy var pictures = [UIImage]()
    // The photo index selected by the current user 
    private var selectedIndex = 0
    //MARK: -  Constructors 
    init(){
        super.init(collectionViewLayout: PicturePickerLayout())
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    //  stay  collectionViewController  in  collectionView ！= view
    override func viewDidLoad() {
        super.viewDidLoad()
        //self.collectionView.backgroundColor = .orange
        self.collectionView!.register(PicturePickerCell.self, forCellWithReuseIdentifier: PicturePickerCellId)
    }
   
    // Photo selector layout 
    private class PicturePickerLayout: UICollectionViewFlowLayout{
        override func prepare() {
            // iOS 9.0  after  ,iPad  Support split screen , It is not recommended to rely too much on  UIScreen  As a layout reference 
            super.prepare()
            let count = 4.0
            let margin = UIScreen.main.scale * 4
            let w = (collectionView!.bounds.width - (count + 1) * margin) / count
            itemSize = CGSize(width: w, height: w)
            sectionInset = UIEdgeInsets(top: margin, left: margin, bottom: 0, right: margin)
            minimumLineSpacing = margin
            minimumInteritemSpacing = margin
        }
    }
}

2. Extended classification , Data source implementation

extension PicturePickerController{
    
    override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        // Make sure there is a plus button at the end   If it reaches the upper limit , No display  +  Button  pictures.count + (pictures.count == PicturePickerMaxCount ? 0 : 1)
        return pictures.count + 1
    }

    override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: PicturePickerCellId, for: indexPath) as! PicturePickerCell
        cell.pictureDelegate = self
        cell.image = indexPath.item < pictures.count ? pictures[indexPath.item] : nil
        cell.hiddenButton = (indexPath.item == PicturePickerMaxCount)
        return cell
    }
}

3. Realization Cell Medium proxy method

//MARK: - PicturePickerCellDelegate
extension PicturePickerController: PicturePickerCellDelegate{
    
    func picturePickerCellDidAdd(cell: PicturePickerCell) {
        
        // Determine whether to allow access to the album 
        /**
          PhotoLibrary   Saved photos  +  Synced photos 
          SavedPhotosAlbum   Saved photos / Screenshot of the screen / Taking pictures 
         */
        if !UIImagePickerController.isSourceTypeAvailable(.savedPhotosAlbum){
            print(" Unable to access Photo Gallery ")
            return
        }
        // Record the photo index selected by the current user 
        selectedIndex =  collectionView!.indexPath(for: cell)?.item ?? 0
        let picker = UIImagePickerController()
        picker.modalPresentationStyle = .fullScreen
        picker.delegate = self
        //picker.allowsEditing = true
        present(picker, animated: true)
    }
    
    func picturePickerCellDidRemove(cell: PicturePickerCell) {
        //1. Get photo index 
        let indexPath = collectionView.indexPath(for: cell)!
        //2. Determine whether the index exceeds the upper limit 
        if indexPath.item >= pictures.count{
            return
        }
        collectionView.performBatchUpdates {
            //3. Delete data 
            pictures.remove(at: indexPath.item)
            //4. Animation refresh data 
            collectionView.deleteItems(at: [indexPath])
        } completion: { finished in
            //5. The refresh data 
            self.collectionView.reloadData()
        }
    }
}

4.UIImagePickerController Abide by the agreement

//MARK: - UIImagePickerController  Abide by the agreement 
extension PicturePickerController: UIImagePickerControllerDelegate, UINavigationControllerDelegate{
    
    ///  Photo selection complete 
    /// - Parameters:
    ///   - picker:  Photo selection controller 
    ///   - info: info  Dictionaries 
    ///   -  Tips ：  Once the proxy method is implemented , Must oneself  dismiss
    func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey : Any]) {
       
        /**
            If you use  cocos2dx  To develop a  ‘ Blank template ’ game , Memory footprint  70M iOS UI  A blank application for , Probably  19M
            General applications , In memory  100M  Both sides are acceptable , No matter how high you are, you need to pay attention 
         */
        let image = info[UIImagePickerController.InfoKey.originalImage] as! UIImage
        let scaleImage = image.scaleToWith(width: 600)
        
        // Add image to array 
        // Judge whether the currently selected index exceeds the array 
        if selectedIndex >= pictures.count{
            pictures.append(scaleImage)
        }else{
            pictures[selectedIndex] = scaleImage
        }
        // Release the controller 
        dismiss(animated: true) {
            // refresh the view 
            self.collectionView.reloadData()
        }
    }
}

5.PicturePickerCellDelegate agent

///PicturePickerCellDelegate  agent 
/// If the agreement includes  optional  Function of , The protocol needs to use  @objc  modification 
@objc
protocol PicturePickerCellDelegate: NSObjectProtocol{
    ///  Add photo 
     @objc optional func picturePickerCellDidAdd(cell: PicturePickerCell)
    ///  Remove the photo 
     @objc optional func picturePickerCellDidRemove(cell: PicturePickerCell)
}

6. Photo selection Cell

// Photo selection  Cell
class PicturePickerCell: UICollectionViewCell{
    
    // Photo selection agent 
    weak var pictureDelegate: PicturePickerCellDelegate?
    
    var image: UIImage? {
        didSet{
            addButton.setImage(image ?? UIImage(named: "compose_pic_add"), for: .normal)
            // Hide delete button  image == nil  Is to add a new button 
            removeButton.isHidden = (image == nil)
        }
    }
    
    var hiddenButton: Bool? {
        didSet{
            addButton.isHidden = hiddenButton ?? false
        }
    }
    
    //MARK: -  Monitoring methods 
    /// Add photo 
     @objc func addPicture(){
         pictureDelegate?.picturePickerCellDidAdd?(cell: self)
    }
    
    /// Remove the photo 
    @objc func removePicture(){
        pictureDelegate?.picturePickerCellDidRemove?(cell: self)
    }
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        setupUI()
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    // Setting controls 
    private func setupUI(){
        //1. add controls 
        contentView.addSubview(addButton)
        contentView.addSubview(removeButton)
        
        //2. Setting up layout 
        addButton.frame = bounds
        removeButton.snp.makeConstraints { make in
            make.top.equalTo(contentView.snp.top)
            make.right.equalTo(contentView.snp.right)
        }
        
        //3. Monitoring methods 
        addButton .addTarget(self, action: #selector(addPicture), for: .touchUpInside)
        removeButton.addTarget(self, action: #selector(removePicture), for: .touchUpInside)
        
        //4. Set fill mode 
        addButton.imageView?.contentMode = .scaleAspectFill
    }
    
    //MARK: -  Lazy load control 
    /// Add a button 
    private lazy var addButton = UIButton(imageName: "compose_pic_add", backImageName: nil)
    /// Delete button 
    private lazy var removeButton = UIButton(imageName: "compose_photo_close", backImageName: nil)
}

7. design sketch