界面搭建 1 （没有自定义cell）

//  PicPickerViewController.swift
//  
//

import UIKit

private let reuseIdentifier = "Cell"

class PicPickerViewController: UICollectionViewController {
    // MARK:- 定义属性
    private lazy var images : [UIImage] = [UIImage]()
    
    // MARK:- 系统回调的函数
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // Register cell classes
        self.collectionView!.registerNib(UINib(nibName: "PicPickerViewCell", bundle: nil), forCellWithReuseIdentifier: reuseIdentifier)
    }
}


// MARK:- CollectioView的数据源方法
extension PicPickerViewController {
    override func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return images.count + 1
    }
    
    override func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
        // 1.创建cell
        let cell = collectionView.dequeueReusableCellWithReuseIdentifier(reuseIdentifier, forIndexPath: indexPath) as! PicPickerViewCell
        
        // 2.给cell设置数据
        cell.backgroundColor = UIColor.redColor()
        cell.image = indexPath.item <= images.count - 1 ? images[indexPath.item] : nil
        cell.delegate = self
        
        return cell
    }
}


// MARK:- Cell的代理方法
extension PicPickerViewController : PicPickerViewCellDelegate {
    func addPhotoBtnClickFor(cell: UICollectionViewCell) {
        // 1.判断照片源是否可用
        if !UIImagePickerController.isSourceTypeAvailable(.PhotoLibrary) {
            return
        }
        
        // 2.创建照片选择控制器
        let ipc = UIImagePickerController()
        
        // 3.设置照片源
        ipc.sourceType = .PhotoLibrary
        
        // 4.设置代理
        ipc.delegate = self
        
        // 6.弹出控制器
        presentViewController(ipc, animated: true, completion: nil)
    }
}


// MARK:- UIImagePickerController的代理方法
extension PicPickerViewController : UIImagePickerControllerDelegate, UINavigationControllerDelegate {
    func imagePickerController(picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : AnyObject]) {
        // 1.取出用户选择的image
        guard let image = info[UIImagePickerControllerOriginalImage] as? UIImage else {
            picker.dismissViewControllerAnimated(true, completion: nil)
            return
        }
        
        // 2.将图片放入到数组中
        images.append(image)
        
        // 3.刷新表格
        collectionView?.reloadData()
        
        // 4.退出照片选择控制器
        picker.dismissViewControllerAnimated(true, completion: nil)
    }
}

// MARK:- 自定义CollectionView的Layout
class PicPickerCollectionViewLayout : UICollectionViewFlowLayout {
    override func prepareLayout() {
        super.prepareLayout()
        
        // 0.定义间距的常量
        let itemPadding : CGFloat = 15
        let itemWH = (UIScreen.mainScreen().bounds.width - 4 * itemPadding) / 3
        
        // 1.设置布局相关的属性
        itemSize = CGSize(width: itemWH, height: itemWH)
        minimumInteritemSpacing = itemPadding
        minimumLineSpacing = itemPadding
        
        // 2.设置collectionView相关的属性
        collectionView?.contentInset = UIEdgeInsets(top: itemPadding, left: itemPadding, bottom: itemPadding, right: itemPadding)
    }
}