我有一个显示基于最新“creationDate”的库照片的UICollectionView。为此，我使用以下代码：
struct AssetsData {
var creationDate: Date, assetResult: PHFetchResult<PHAsset>
}
func fetchPhotos() -> [AssetsData] {
//Date Formatter
let formatter = DateFormatter()
formatter.dateStyle = DateFormatter.Style.medium
formatter.timeStyle = DateFormatter.Style.none
//Photos fetch
let fetchOptions = PHFetchOptions()
let sortOrder = [NSSortDescriptor(key: "creationDate", ascending: false)]
fetchOptions.sortDescriptors = sortOrder
let assetsFetchResult = PHAsset.fetchAssets(with: .image, options: fetchOptions)
var arrCreationDate = [Date]()
var arrDates = [String]()
//Getting All dates
for index in 0..<assetsFetchResult.count {
if let creationDate = assetsFetchResult[index].creationDate {
let formattedDate = formatter.string(from: creationDate)
if !arrDates.contains(formattedDate) {
arrDates.append(formattedDate)
arrCreationDate.append(creationDate)
}
}
}
//Fetching Assets based on Dates
var arrPhotoAssetsData = [AssetsData]()
for createdDate in arrCreationDate {
if let startDate = getDate(forDay: createdDate.day, forMonth: createdDate.month, forYear: createdDate.year, forHour: 0, forMinute: 0, forSecond: 0), let endDate = getDate(forDay: createdDate.day, forMonth: createdDate.month, forYear: createdDate.year, forHour: 23, forMinute: 59, forSecond: 59) {
fetchOptions.predicate = NSPredicate(format: "creationDate > %@ AND creationDate < %@", startDate as NSDate, endDate as NSDate)
let assetsPhotoFetchResult = PHAsset.fetchAssets(with: PHAssetMediaType.image, options: fetchOptions)
arrPhotoAssetsData.append(AssetsData(creationDate: createdDate, assetResult: assetsPhotoFetchResult))
}
}
return arrPhotoAssetsData
}
func getDate(forDay day: Int, forMonth month: Int, forYear year: Int, forHour hour: Int, forMinute minute: Int, forSecond second: Int) -> Date? {
var dateComponents = DateComponents()
dateComponents.day = day
dateComponents.month = month
dateComponents.year = year
dateComponents.hour = hour
dateComponents.minute = minute
dateComponents.second = second
var gregorian = Calendar(identifier: Calendar.Identifier.gregorian)
gregorian.timeZone = NSTimeZone.system
return gregorian.date(from: dateComponents)
}
代码工作得很好！但问题是加载10k+照片需要7-9秒。直到6k照片没有问题，但我真的需要一些有效的方法，以便我可以加载一些
asset中的UICollectionView，其余的我可以添加以后。我需要的是，不管照片的数量，不应该超过2-3秒。有人能帮忙吗？ 最佳答案
假设你有八千张照片。因此，您将遍历两个“for”循环，以获得arrCreationDate和arrPhotoAssets数据（这是所需工作的两倍）
相反，你可以尝试通过一个循环来完成。有一个粗略的方法：-
let assetsFetchResult = PHAsset.fetchAssets(with: .image, options: fetchOptions)
let fetchOptions = PHFetchOptions()
var arrCreationDate = [Date]()
var arrPhotoAssetsData = [AssetsData]()
var arrDates = [String]()
for index in 0..<assetsFetchResult.count {
if let creationDate = assetsFetchResult[index].creationDate {
let formattedDate = formatter.string(from: creationDate)
if !arrDates.contains(formattedDate) {
//You can convert the formattedDate to actual date here and do a check similar to this, do what you do in the other loop here too
if(actualDate < actualDateOfTheFirstElementAtArray){
arrCreationDate.insert(actualDate, at: 0)
fetchOptions.predicate = NSPredicate(format: "creationDate > %@ AND creationDate < %@", startDate as NSDate, endDate as NSDate)
let assetsPhotoFetchResult = PHAsset.fetchAssets(with: PHAssetMediaType.image, options: fetchOptions)
arrPhotoAssetsData.insert(AssetsData(creationDate: createdDate, assetResult: assetsPhotoFetchResult), at: 0)
}
}
}
}
这只是为了让你大致了解我在说什么，因为这样可以减轻一半的负担（只是一个循环）
也可以尝试使用集合视图的预取数据源来预加载一些数据
编辑：-
我想你已经试过了：-
func fetchPhotos() -> [AssetsData] {
//Date Formatter
let formatter = DateFormatter()
formatter.dateStyle = DateFormatter.Style.medium
formatter.timeStyle = DateFormatter.Style.none
//Photos fetch
let fetchOptions = PHFetchOptions()
let sortOrder = [NSSortDescriptor(key: "creationDate", ascending: false)]
fetchOptions.sortDescriptors = sortOrder
let assetsFetchResult = PHAsset.fetchAssets(with: .image, options: fetchOptions)
var arrCreationDate = [Date]()
var arrDates = [String]()
var arrPhotoAssetsData = [AssetsData]()
//Getting All dates
for index in 0..<assetsFetchResult.count {
if let creationDate = assetsFetchResult[index].creationDate {
let formattedDate = formatter.string(from: creationDate)
if !arrDates.contains(formattedDate) {
arrDates.append(formattedDate)
arrCreationDate.append(creationDate)
convertToAssetsDataAndAppend(date: creationDate, fetchOptions: fetchOptions, toArray: &arrPhotoAssetsData)
}
}
}
return arrPhotoAssetsData
}
func convertToAssetsDataAndAppend(date: Date, fetchOptions: PHFetchOptions, toArray: inout [AssetsData]){
if let startDate = getDate(forDay: date.day, forMonth: date.month, forYear: date.year, forHour: 0, forMinute: 0, forSecond: 0), let endDate = getDate(forDay: date.day, forMonth: date.month, forYear: date.year, forHour: 23, forMinute: 59, forSecond: 59) {
fetchOptions.predicate = NSPredicate(format: "creationDate > %@ AND creationDate < %@", startDate as NSDate, endDate as NSDate)
let assetsPhotoFetchResult = PHAsset.fetchAssets(with: PHAssetMediaType.image, options: fetchOptions)
toArray.append(AssetsData(creationDate: date, assetResult: assetsPhotoFetchResult))
}
}
func getDate(forDay day: Int, forMonth month: Int, forYear year: Int, forHour hour: Int, forMinute minute: Int, forSecond second: Int) -> Date? {
var dateComponents = DateComponents()
dateComponents.day = day
dateComponents.month = month
dateComponents.year = year
dateComponents.hour = hour
dateComponents.minute = minute
dateComponents.second = second
var gregorian = Calendar(identifier: Calendar.Identifier.gregorian)
gregorian.timeZone = NSTimeZone.system
return gregorian.date(from: dateComponents)
}
如果这不起作用，那么在每次循环迭代之后用某种回调重新加载collection视图怎么样？（采用上述方法）
这样，你就不会让用户等到整个东西都加载了
Idk，这些看起来可能很小，但我只是想帮忙：）
关于swift - 在Swift [Faster Way？]中基于creationDate从图库中获取所有照片。，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/53098339/