Ios 如何在UICollectionView中对照片库中的图像进行分页

我已经在UICollectionView中从photoLibrary导入了图像，collectionView在collectionView中初始化照片需要花费大量时间，因此我需要通过垂直滚动对这些图像进行分页。首先，我想在collectionView中加载10个图像，然后用户对加载10个图像进行分页，然后继续此过程

import UIKit
import Photos
import XLPagerTabStrip

private let reuseIdentifier = "Cell"

class PhotosRecyclerCollection: UICollectionViewController, UICollectionViewDelegateFlowLayout, UINavigationControllerDelegate {

    var imageArray = [UIImage]()

    override func viewDidLoad() {
        grabPhotos()
    }

    func grabPhotos(){

        let imgManager = PHImageManager.default()

        let requestOptions = PHImageRequestOptions()
        requestOptions.isSynchronous = true
        requestOptions.deliveryMode = .highQualityFormat

        let fetchOptions = PHFetchOptions()
        fetchOptions.sortDescriptors = [NSSortDescriptor(key: "creationDate", ascending: false)]

        if let fetchResult : PHFetchResult = PHAsset.fetchAssets(with: .image, options: fetchOptions) {

            if fetchResult.count > 0 {

                for i in 0..<fetchResult.count{

                    imgManager.requestImage(for: fetchResult.object(at: i) as! PHAsset, targetSize: CGSize(width: 200, height: 200), contentMode: .aspectFill, options: requestOptions, resultHandler: {

                        image , error in

                        self.imageArray.append(image!)
                    })
                }
            }

            else {

                print("You got no photos")

                self.collectionView?.reloadData()
            }
        }

    }





    override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return imageArray.count
    }

    override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "PhotosCollectionViewCell", for: indexPath) as! PhotosCollectionViewCell

        let imageView = cell.viewWithTag(1) as! UIImageView

        imageView.image = imageArray[indexPath.row]

        return cell
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {

        let width = collectionView.frame.width / 4 - 1


        return CGSize(width: width, height: width)



    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
        return 1.0
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
        return 1.0
    }

    override func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        let mainStoryBoard:UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
        let desVC = mainStoryBoard.instantiateViewController(withIdentifier: "imageCropper") as! ImageCropperViewController
        desVC.image = imageArray[indexPath.row]
        self.navigationController?.pushViewController(desVC, animated: true)
    }

}

导入UIKit
导入照片
导入XLPagerTabStrip
private let reuseIdentifier=“Cell”
类PhotoRecyclerCollection:UICollectionViewController、UICollectionViewDelegateFlowLayout、UINavigationControllerDelegate{
var imageArray=[UIImage]（）
重写func viewDidLoad（）{
抓取照片（）
}
func grabPhotos（）{
让imgManager=PHImageManager.default（）
让requestOptions=PHImageRequestOptions（）
requestOptions.isSynchronous=true
requestOptions.deliveryMode=.highQualityFormat
让fetchOptions=PHFetchOptions（）
fetchOptions.sortDescriptors=[NSSortDescriptor（键：“creationDate”，升序：false）]
如果让fetchResult:PHFetchResult=PHAsset.fetchAssets（带：。图像，选项：fetchOptions）{
如果fetchResult.count>0{
对于0..Int中的i{
返回imageArray.count
}
重写func collectionView（collectionView:UICollectionView，cellForItemAt indexPath:indexPath）->UICollectionViewCell{
让cell=collectionView.dequeueReusableCell（带有reuseidentifier:“photocollectionviewcell”，for:indexath）作为！photocollectionviewcell
让imageView=cell.viewWithTag（1）为！UIImageView
imageView.image=imageArray[indexPath.row]
返回单元
}
func collectionView（collectionView:UICollectionView，布局collectionViewLayout:UICollectionViewLayout，sizeForItemAt indexPath:indexPath）->CGSize{
let width=collectionView.frame.width/4-1
返回CGSize（宽度：宽度，高度：宽度）
}
func collectionView（collectionView:UICollectionView，布局collectionViewLayout:UICollectionViewLayout，MinimumLineSpacingforSection:Int）->CGFloat{
返回1.0
}
func collectionView（collectionView:UICollectionView，布局collectionViewLayout:UICollectionViewLayout，MinimumItemSpacingForSection:Int）->CGFloat{
返回1.0
}
重写func collectionView（collectionView:UICollectionView，didSelectItemAt indexPath:indexPath）{
let mainStoryBoard:UIStoryboard=UIStoryboard（名称：“Main”，bundle:nil）
让desVC=mainStoryBoard.instanceeviewcontroller（标识符为：“imageCropper”）作为！ImageCropperServicewcontroller
desVC.image=imageArray[indexPath.row]
self.navigationController？.pushViewController（desVC，动画：true）
}
}

您不需要分页。因为您正在预加载所有图像，所以加载需要花费大量时间

只需停止在内存中预加载图像，并在实际需要时获取相关图像即可

为此，添加

fetchResult

作为实例变量：

private var fetchResult: PHFetchResult?

替换

if let fetchResult : PHFetchResult = PHAsset.fetchAssets(with: .image, options: fetchOptions) {

            if fetchResult.count > 0 {

                for i in 0..<fetchResult.count{

                    imgManager.requestImage(for: fetchResult.object(at: i) as! PHAsset, targetSize: CGSize(width: 200, height: 200), contentMode: .aspectFill, options: requestOptions, resultHandler: {

                        image , error in

                        self.imageArray.append(image!)
                    })
                }
            }

将

返回imageArray.count

替换为

返回self.fetchResult？.count±0

最后：

let imageView = cell.viewWithTag(1) as! UIImageView
imageView.image = imageArray[indexPath.row]

与

---

您不需要分页。因为您正在预加载所有图像，所以加载需要很多时间

只需停止在内存中预加载图像，并在实际需要时获取相关图像即可

为此，添加

fetchResult

作为实例变量：

private var fetchResult: PHFetchResult?

替换

if let fetchResult : PHFetchResult = PHAsset.fetchAssets(with: .image, options: fetchOptions) {

            if fetchResult.count > 0 {

                for i in 0..<fetchResult.count{

                    imgManager.requestImage(for: fetchResult.object(at: i) as! PHAsset, targetSize: CGSize(width: 200, height: 200), contentMode: .aspectFill, options: requestOptions, resultHandler: {

                        image , error in

                        self.imageArray.append(image!)
                    })
                }
            }

将

返回imageArray.count

替换为

返回self.fetchResult？.count±0

最后：

let imageView = cell.viewWithTag(1) as! UIImageView
imageView.image = imageArray[indexPath.row]

与

---

当我滚动collectionView时，我的图像在几毫秒后刷新，首先显示随机图像，然后更改为实际图像。当我滚动collectionView时，我的图像在几毫秒后刷新，首先显示随机图像，然后更改为实际图像。