Avoiding duplicates when getting pictures with PHA

问题:

On iOS 8, I want to get all pictures stored on the device. My problem is that I do get them, but some are present more than once. The PHAsset properties (hidden, mediaSubtypes, etc.) are the same for all pictures, so I can't for example rule out the PHAssetMediaSubtypePhotoHDR subtypes. The only way I found is not adding multiple pictures with the same date, but this is a problem when multiple photos were saved with the same creation date.

Does anybody know why I get these duplicates and what I can do to avoid them?

This is how I get the pictures:

    PHFetchOptions *fetchOptions = [PHFetchOptions new];
    fetchOptions.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"creationDate" ascending:YES],];
    PHFetchResult *phAssets = [PHAsset fetchAssetsWithMediaType:PHAssetMediaTypeImage options:fetchOptions];

回答1:

You can try to use Moments Collections:

PHFetchResult * moments = [PHAssetCollection fetchMomentsWithOptions:nil];            
for (PHAssetCollection * moment in moments) {
    PHFetchResult * assetsFetchResults = [PHAsset fetchAssetsInAssetCollection:moment options:nil];
    for (PHAsset * asset in assetsFetchResults) {
        //Do something with asset, for example add them to array
    }
}

回答2:

Since iOS 8.1, the behavior of the fetchAssetsWithMediaType: and fetchAssetsWithOptions: methods has changed, and they no longer include photos synchronized to the device from iTunes or photos stored in an iCloud Shared Photo Stream.

Source: Document Revision History and PHAsset Class Reference.

回答3:

I had the same problem, and for me, the duplicates were images that were in the my photostream album. To work around the issue, i now use the FetchMoments method from the PHAssetCollection class, and then I fetch all assets for each moment in the fetch result. This way i get all images without getting repeated images.

If someone finds a better solution, please let me know.

回答4:

On a flyer, are these assets are part of a burst? (cf. PHAsset.burstIdentifier, etc.) If so, you can adjust accordingly.

回答5:

you can use the "PHImageRequestOptions" to setup only high quality images for example!

//Setting up the deliveryMode in PHImageRequestOptions()
fileprivate func imageRequestOptions() -> PHImageRequestOptions {
    let requestOption = PHImageRequestOptions()
    requestOption.deliveryMode = .highQualityFormat
    return requestOption
}

fileprivate func fetchImages(){

    let fetchOptions = assetsFetchOptions() //get fetchOptions only. Don`t worry
    let allPhotos = PHAsset.fetchAssets(with: .image, options: fetchOptions)

    allPhotos.enumerateObjects({ (asset, index, stop) in
        print(asset)

        let imageManager = PHImageManager.default()
        let targetSize = CGSize(width: 200, height: 200)

        //This function uses the "imageRequestOptions()" function to set up the "options:" field in this .requestImage() function.
        imageManager.requestImage(for: asset, targetSize: targetSize, contentMode: .aspectFit, options: self.imageRequestOptions(), resultHandler: { (image, info) in

            if let image = image {
                self.images.append(image)
                self.assets.append(asset)

                if self.selectedImage == nil {
                    self.selectedImage = image
                }
            }

            if index == allPhotos.count - 1 {
                self.collectionView?.reloadData()
            }
        })
    })
}