iOS实现微信/QQ显示最近拍摄图片的功能实例代码

import UIKit import Photos //使用图库功能时必须引用这个包 //显示最近拍摄的照片为缩略图 class ViewController: UIViewController, PHPhotoLibraryChangeObserver {  var assetsFetchResults:PHFetchResult<PHAsset>!  var imageManager: PHCachingImageManager! //带缓存的图片管理对象  var imageView: UIImageView! //用于显示缩略图  var assetGridThumbnailSize: CGSize! //缩略图大小  override func viewDidLoad() {   super.viewDidLoad()   // Do any additional setup after loading the view, typically from a nib.   imageView = UIImageView()   imageView.frame = CGRect(x: 50, y: 50, width: 100, height: 100)   imageView.contentMode = .scaleAspectFit   imageView.clipsToBounds = true   self.view.addSubview(imageView)   self.imageManager = PHCachingImageManager() //初始化和充值缓存   let scale = UIScreen.main.scale //像素比   assetGridThumbnailSize = CGSize(width: imageView.frame.width*scale,           height: imageView.frame.height*scale)   //申请权限   PHPhotoLibrary.requestAuthorization({ (status) in    if status != .authorized {     return    }    //获取所有图片资源(按照创建时间排序)    let allPhotoOptions = PHFetchOptions()    allPhotoOptions.sortDescriptors = [NSSortDescriptor(key: "creationDate",                 ascending: false)] //排序方式    allPhotoOptions.predicate = NSPredicate(format: "mediaType = %d",              PHAssetMediaType.image.rawValue) //类型    self.assetsFetchResults = PHAsset.fetchAssets(with: .image,                options: allPhotoOptions) //查询照片类型    var i = 0    while i<self.assetsFetchResults.count {     let asset = self.assetsFetchResults[i]     print(" 创建时间：/(asset.creationDate?.description)") //打印所有图片的创建时间     i += 1    }    if (self.assetsFetchResults.count > 0) {     //显示最近一张拍摄的图片（也可以根据拍摄时间远近决定是否要显示）     self.imageManager.requestImage(for: self.assetsFetchResults[0],  //最近一张图片             targetSize: self.assetGridThumbnailSize,             contentMode: .aspectFill,             options: nil, resultHandler: { (image, info) in             self.imageView.image = image //取出图像并显示出来     })    }    print("图片数量：/(self.assetsFetchResults?.count)")    //注册监听资源变化    PHPhotoLibrary.shared().register(self) //删除是unregisterChangeObserver   })  }  override func didReceiveMemoryWarning() {   super.didReceiveMemoryWarning()   // Dispose of any resources that can be recreated.  }  func photoLibraryDidChange(_ changeInstance: PHChange) {   guard let changes = changeInstance.changeDetails(for: self.assetsFetchResults as! PHFetchResult<PHObject>) else {    return   }   //异步执行，避免阻塞图片变化事件队列   DispatchQueue.main.async {    if let result = changes.fetchResultAfterChanges as? PHFetchResult<PHAsset> {     self.assetsFetchResults = result //差异结果    }    //判断是否有新增图片或删除图片的情况    if !changes.hasIncrementalChanges || changes.hasMoves {     return    } else {     print("图片数据有变化")     if let indexs = changes.changedIndexes, indexs.count>0 { //不显示0的情况      print("有/(indexs.count)张图片发生变化")     }     if let removes = changes.removedIndexes, removes.count>0 {      print("删除了/(removes.count)张图片")     }     if let inserts = changes.insertedIndexes, inserts.count>0 {      //有新增图片      print("新增了/(inserts.count)张图片")      let picture = self.assetsFetchResults[inserts.first!]      self.imageManager.requestImage(for: picture,              targetSize: self.assetGridThumbnailSize,              contentMode: .aspectFill,              options: nil, resultHandler: { (image, option) in              self.imageView.image = image //取出图像并显示出来      })     }    }   }  } }