如何正确使用具有本地标识符的获取资产？
How do I correctly use fetch assets with a local identifier?
我正在尝试弄清楚如何获取标识符数组并以编程方式将它们放入集合视图中。如果我错了请纠正我，但我相信最好的方法是使用 PHAsset.fetchAssets。我最多预计用户会获取 10 张图像（平均 3-4 张），因此我认为该过程不会占用大量资源。我正在使用特定的标识符数组测试下面的代码。在我分配资产的那一行的 cellForItemAt 函数中，我收到一条错误消息。请参阅该行上方的注释。我在 SO 上看到过类似的问题，但我无法应用我发现的任何内容。我做错了什么？
var identifier: [String] = ["83BDF9C0-E1FB-4F68-9F2C-99649A67E218/L0/001", "18D08CEC-4075-4488-BFD1-E9403B214356/L0/001", "74257416-6D9C-48B2-9CE0-C23B56CB4171/L0/001", "2EA7CACE-9B9B-4FC9-ABC5-03BCE2BDAA2A/L0/001", "46A4CD2B-4FEB-4BBE-86DC-B79ED49BC300/L0/001", "E4290EB0-2B16-46AE-9B98-83379F6128F3/L0/001", "7C0B36FF-320D-4083-92E4-5A1F464FFFB1/L0/001", "DEE1414C-2B92-4147-8C3C-A1775FB324AD/L0/001"]
class DetailViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout{
var myCollectionView: UICollectionView!
let imgManager = PHImageManager.default()
let requestOptions = PHImageRequestOptions()
var fetchResult: PHFetchResult<PHAsset>!
override func viewDidLoad() {
requestOptions.isSynchronous = false
requestOptions.deliveryMode = .opportunistic
let layout = UICollectionViewFlowLayout()
myCollectionView = UICollectionView(frame: self.view.frame, collectionViewLayout: layout)
myCollectionView.delegate = self
myCollectionView.dataSource = self
myCollectionView.backgroundColor = UIColor.white
myCollectionView.allowsMultipleSelection = true
myCollectionView.register(ImageEditCell.self, forCellWithReuseIdentifier: "Cell")
myCollectionView.showsVerticalScrollIndicator = false
self.view.addSubview(myCollectionView)
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as! ImageEditCell
cell.representedAssetIdentifier = identifier[0]
let requestOptions = PHImageRequestOptions()
requestOptions.isSynchronous = false
// LINE BELOW PRODUCES ERROR: Cannot convert value of type '[String]' to expected element type 'Array<String>.ArrayLiteralElement' (aka 'String')
let asset = PHAsset.fetchAssets(withLocalIdentifiers: [identifier], options: .none).firstObject
imgManager.requestImage(for: asset!, targetSize: CGSize(width:120, height: 120),
contentMode: .aspectFill,
options: requestOptions,
resultHandler: { result, info in
if cell.representedAssetIdentifier == self.identifier {
cell.imageview.image = result
}
})
}
}
在这里，我已将获取功能移至 viewDidLoad 以防止出现其他错误，而且我不确定您要获取的内容是否是带有图像的数组（如果是，则通过放置 .firstObject 获取单个图片可能会导致错误）
var identifier: [String] = ["83BDF9C0-E1FB-4F68-9F2C-99649A67E218/L0/001", "18D08CEC-4075-4488-BFD1-E9403B214356/L0/001", "74257416-6D9C-48B2-9CE0-C23B56CB4171/L0/001", "2EA7CACE-9B9B-4FC9-ABC5-03BCE2BDAA2A/L0/001", "46A4CD2B-4FEB-4BBE-86DC-B79ED49BC300/L0/001", "E4290EB0-2B16-46AE-9B98-83379F6128F3/L0/001", "7C0B36FF-320D-4083-92E4-5A1F464FFFB1/L0/001", "DEE1414C-2B92-4147-8C3C-A1775FB324AD/L0/001"]
class DetailViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout{
var myCollectionView: UICollectionView!
let imgManager = PHImageManager.default()
let requestOptions = PHImageRequestOptions()
var fetchResult: PHFetchResult<PHAsset>!
override func viewDidLoad() {
let requestOptions = PHImageRequestOptions()
requestOptions.isSynchronous = false
let layout = UICollectionViewFlowLayout()
myCollectionView = UICollectionView(frame: self.view.frame, collectionViewLayout: layout)
myCollectionView.delegate = self
myCollectionView.dataSource = self
myCollectionView.backgroundColor = UIColor.white
myCollectionView.allowsMultipleSelection = true
myCollectionView.register(ImageEditCell.self, forCellWithReuseIdentifier: "Cell")
myCollectionView.showsVerticalScrollIndicator = false
self.view.addSubview(myCollectionView)
let asset = PHAsset.fetchAssets(withLocalIdentifiers: [identifier], options: .none)
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as! ImageEditCell
cell.representedAssetIdentifier = identifier[indexPath.row]
imgManager.requestImage(for: asset!, targetSize: CGSize(width:120, height: 120),
contentMode: .aspectFill,
options: requestOptions,
resultHandler: { result, info in
if cell.representedAssetIdentifier == self.identifier {
cell.imageview.image = result
}
})
}
}
我终于明白了。我意识到我没有正确地将标识符转换为 UIImage，所以即使我修复了 OP 中的错误，它仍然无法工作，因为许多其他人会提出该解决方案。以下是我开始工作的解决方案：
var myCollectionView: UICollectionView!
var imageViews = [UIImageView]()
var identifier = [
"83BDF9C0-E1FB-4F68-9F2C-99649A67E218/L0/001",
"18D08CEC-4075-4488-BFD1-E9403B214356/L0/001",
"74257416-6D9C-48B2-9CE0-C23B56CB4171/L0/001",
"2EA7CACE-9B9B-4FC9-ABC5-03BCE2BDAA2A/L0/001",
"46A4CD2B-4FEB-4BBE-86DC-B79ED49BC300/L0/001",
"E4290EB0-2B16-46AE-9B98-83379F6128F3/L0/001",
"7C0B36FF-320D-4083-92E4-5A1F464FFFB1/L0/001",
"DEE1414C-2B92-4147-8C3C-A1775FB324AD/L0/001"
]
override func viewDidLoad() {
let layout = UICollectionViewFlowLayout()
myCollectionView = UICollectionView(frame: self.view.frame, collectionViewLayout: layout)
myCollectionView.delegate = self
myCollectionView.dataSource = self
myCollectionView.backgroundColor = UIColor.white
myCollectionView.allowsMultipleSelection = true
myCollectionView.showsVerticalScrollIndicator = false
myCollectionView.register(CollectionCell.self, forCellWithReuseIdentifier: "Cell")
self.view.addSubview(myCollectionView)
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return identifier.count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as! CollectionCell
let options = PHFetchOptions()
let results = PHAsset.fetchAssets(withLocalIdentifiers: identifier, options: options)
let manager = PHImageManager.default()
results.enumerateObjects { (thisAsset, _, _) in
manager.requestImage(for: thisAsset, targetSize: CGSize(width: 200.0, height: 200.0), contentMode: .aspectFit, options: nil, resultHandler: {(thisImage, _) in
self.imageViews.append(UIImageView(image: thisImage))
})
}
let image = imageViews[indexPath.item]
cell.imageView.image = image.image
return cell
}
我正在尝试弄清楚如何获取标识符数组并以编程方式将它们放入集合视图中。如果我错了请纠正我，但我相信最好的方法是使用 PHAsset.fetchAssets。我最多预计用户会获取 10 张图像（平均 3-4 张），因此我认为该过程不会占用大量资源。我正在使用特定的标识符数组测试下面的代码。在我分配资产的那一行的 cellForItemAt 函数中，我收到一条错误消息。请参阅该行上方的注释。我在 SO 上看到过类似的问题，但我无法应用我发现的任何内容。我做错了什么？
var identifier: [String] = ["83BDF9C0-E1FB-4F68-9F2C-99649A67E218/L0/001", "18D08CEC-4075-4488-BFD1-E9403B214356/L0/001", "74257416-6D9C-48B2-9CE0-C23B56CB4171/L0/001", "2EA7CACE-9B9B-4FC9-ABC5-03BCE2BDAA2A/L0/001", "46A4CD2B-4FEB-4BBE-86DC-B79ED49BC300/L0/001", "E4290EB0-2B16-46AE-9B98-83379F6128F3/L0/001", "7C0B36FF-320D-4083-92E4-5A1F464FFFB1/L0/001", "DEE1414C-2B92-4147-8C3C-A1775FB324AD/L0/001"]
class DetailViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout{
var myCollectionView: UICollectionView!
let imgManager = PHImageManager.default()
let requestOptions = PHImageRequestOptions()
var fetchResult: PHFetchResult<PHAsset>!
override func viewDidLoad() {
requestOptions.isSynchronous = false
requestOptions.deliveryMode = .opportunistic
let layout = UICollectionViewFlowLayout()
myCollectionView = UICollectionView(frame: self.view.frame, collectionViewLayout: layout)
myCollectionView.delegate = self
myCollectionView.dataSource = self
myCollectionView.backgroundColor = UIColor.white
myCollectionView.allowsMultipleSelection = true
myCollectionView.register(ImageEditCell.self, forCellWithReuseIdentifier: "Cell")
myCollectionView.showsVerticalScrollIndicator = false
self.view.addSubview(myCollectionView)
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as! ImageEditCell
cell.representedAssetIdentifier = identifier[0]
let requestOptions = PHImageRequestOptions()
requestOptions.isSynchronous = false
// LINE BELOW PRODUCES ERROR: Cannot convert value of type '[String]' to expected element type 'Array<String>.ArrayLiteralElement' (aka 'String')
let asset = PHAsset.fetchAssets(withLocalIdentifiers: [identifier], options: .none).firstObject
imgManager.requestImage(for: asset!, targetSize: CGSize(width:120, height: 120),
contentMode: .aspectFill,
options: requestOptions,
resultHandler: { result, info in
if cell.representedAssetIdentifier == self.identifier {
cell.imageview.image = result
}
})
}
}
在这里，我已将获取功能移至 viewDidLoad 以防止出现其他错误，而且我不确定您要获取的内容是否是带有图像的数组（如果是，则通过放置 .firstObject 获取单个图片可能会导致错误）
var identifier: [String] = ["83BDF9C0-E1FB-4F68-9F2C-99649A67E218/L0/001", "18D08CEC-4075-4488-BFD1-E9403B214356/L0/001", "74257416-6D9C-48B2-9CE0-C23B56CB4171/L0/001", "2EA7CACE-9B9B-4FC9-ABC5-03BCE2BDAA2A/L0/001", "46A4CD2B-4FEB-4BBE-86DC-B79ED49BC300/L0/001", "E4290EB0-2B16-46AE-9B98-83379F6128F3/L0/001", "7C0B36FF-320D-4083-92E4-5A1F464FFFB1/L0/001", "DEE1414C-2B92-4147-8C3C-A1775FB324AD/L0/001"]
class DetailViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout{
var myCollectionView: UICollectionView!
let imgManager = PHImageManager.default()
let requestOptions = PHImageRequestOptions()
var fetchResult: PHFetchResult<PHAsset>!
override func viewDidLoad() {
let requestOptions = PHImageRequestOptions()
requestOptions.isSynchronous = false
let layout = UICollectionViewFlowLayout()
myCollectionView = UICollectionView(frame: self.view.frame, collectionViewLayout: layout)
myCollectionView.delegate = self
myCollectionView.dataSource = self
myCollectionView.backgroundColor = UIColor.white
myCollectionView.allowsMultipleSelection = true
myCollectionView.register(ImageEditCell.self, forCellWithReuseIdentifier: "Cell")
myCollectionView.showsVerticalScrollIndicator = false
self.view.addSubview(myCollectionView)
let asset = PHAsset.fetchAssets(withLocalIdentifiers: [identifier], options: .none)
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as! ImageEditCell
cell.representedAssetIdentifier = identifier[indexPath.row]
imgManager.requestImage(for: asset!, targetSize: CGSize(width:120, height: 120),
contentMode: .aspectFill,
options: requestOptions,
resultHandler: { result, info in
if cell.representedAssetIdentifier == self.identifier {
cell.imageview.image = result
}
})
}
}
我终于明白了。我意识到我没有正确地将标识符转换为 UIImage，所以即使我修复了 OP 中的错误，它仍然无法工作，因为许多其他人会提出该解决方案。以下是我开始工作的解决方案：
var myCollectionView: UICollectionView!
var imageViews = [UIImageView]()
var identifier = [
"83BDF9C0-E1FB-4F68-9F2C-99649A67E218/L0/001",
"18D08CEC-4075-4488-BFD1-E9403B214356/L0/001",
"74257416-6D9C-48B2-9CE0-C23B56CB4171/L0/001",
"2EA7CACE-9B9B-4FC9-ABC5-03BCE2BDAA2A/L0/001",
"46A4CD2B-4FEB-4BBE-86DC-B79ED49BC300/L0/001",
"E4290EB0-2B16-46AE-9B98-83379F6128F3/L0/001",
"7C0B36FF-320D-4083-92E4-5A1F464FFFB1/L0/001",
"DEE1414C-2B92-4147-8C3C-A1775FB324AD/L0/001"
]
override func viewDidLoad() {
let layout = UICollectionViewFlowLayout()
myCollectionView = UICollectionView(frame: self.view.frame, collectionViewLayout: layout)
myCollectionView.delegate = self
myCollectionView.dataSource = self
myCollectionView.backgroundColor = UIColor.white
myCollectionView.allowsMultipleSelection = true
myCollectionView.showsVerticalScrollIndicator = false
myCollectionView.register(CollectionCell.self, forCellWithReuseIdentifier: "Cell")
self.view.addSubview(myCollectionView)
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return identifier.count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as! CollectionCell
let options = PHFetchOptions()
let results = PHAsset.fetchAssets(withLocalIdentifiers: identifier, options: options)
let manager = PHImageManager.default()
results.enumerateObjects { (thisAsset, _, _) in
manager.requestImage(for: thisAsset, targetSize: CGSize(width: 200.0, height: 200.0), contentMode: .aspectFit, options: nil, resultHandler: {(thisImage, _) in
self.imageViews.append(UIImageView(image: thisImage))
})
}
let image = imageViews[indexPath.item]
cell.imageView.image = image.image
return cell
}