从用户照片库中获取最后一张照片，返回两张照片

Posted 2023-02-23

【中文标题】从用户照片库中获取最后一张照片，返回两张照片

【英文标题】：Getting last picture taken from users photo library returning two pictures

【发布时间】：2015-09-07 01:54:12

【问题描述】：

使用以下代码时，它会获取我的最后一张图片，但会复制它。它总是得到最后一张图片，但它成对返回：

UIImageView *imageView = (UIImageView *) [self.photoCollectionView viewWithTag:101];
PHFetchOptions *fetchOptions = [[PHFetchOptions alloc] init];
fetchOptions.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"creationDate" ascending:YES]];
PHFetchResult *fetchResult = [PHAsset fetchAssetsWithMediaType:PHAssetMediaTypeImage options:fetchOptions];
PHAsset *lastAsset = [fetchResult lastObject];
[[PHImageManager defaultManager] requestImageForAsset:lastAsset
                                targetSize:imageView.bounds.size
                                contentMode:PHImageContentModeAspectFill
                                options:nil
                                resultHandler:^(UIImage *result, NSDictionary *info) 
                                NSLog(@"PHImageManager request results %@ and info %@", result, info);
                                dispatch_async(dispatch_get_main_queue(), ^
                                    [user_photos addObject:result];
                                    NSLog(@"%lu",user_photos.count);
                                    [self.photoCollectionView reloadData];
                                    NSLog(@"%lu",user_photos.count);
                                );
];

发生这种情况的任何原因？以下是日志语句：

2015-09-06 21:48:22.153[41357:11390462] PHImageManager request results <UIImage: 0x7fd1336b8f40>, 60, 40 and info 
PHImageFileOrientationKey = 0;
PHImageResultDeliveredImageFormatKey = 4031;
PHImageResultIsDegradedKey = 1;
PHImageResultRequestIDKey = 1;
PHImageResultWantedImageFormatKey = 5003;

2015-09-06 21:48:22.158[41357:11390462] 2
2015-09-06 21:48:22.159[41357:11390462] 2

2015-09-06 21:48:22.166[41357:11390462] PHImageManager request results <UIImage: 0x7fd13374c3b0>, 386, 256 and info 
PHImageFileOrientationKey = 0;
PHImageResultDeliveredImageFormatKey = 5003;
PHImageResultIsDegradedKey = 0;
PHImageResultRequestIDKey = 1;
PHImageResultWantedImageFormatKey = 5003;

2015-09-06 21:48:22.167[41357:11390462] 3
2015-09-06 21:48:22.167[41357:11390462] 3

这发生在模拟器和设备上。不使用第 3 方软件，没关系，我想。为什么会被调用两次？我在 uialertaction 块中调用它

【参考方案1】：

好吧，在对“PHImageResultIsDegradedKey”的作用和作用进行了一些研究之后，很自然地，它归结为操作系统正在检索图像数据，在它得到它之后，它正在根据设置调整它的大小以实现质量输出，这就是我看到的原因第二张图片。

所以我所做的是在实际请求资产之前添加 PHImageRequestOptions 参数，它只检索到我想要的照片：

...
PHAsset *lastAsset = [fetchResult lastObject];
PHImageRequestOptions * options = [[PHImageRequestOptions alloc] init];
options.deliveryMode = PHImageRequestOptionsDeliveryModeHighQualityFormat;
options.synchronous = NO;
options.resizeMode = PHImageRequestOptionsVersionOriginal;
options.networkAccessAllowed = NO;
[[PHImageManager defaultManager] requestImageForAsset:lastAsset
                             targetSize:imageView.bounds.size
                             contentMode:PHImageContentModeAspectFit
                             options:options
                             resultHandler:^(UIImage *result, NSDictionary *info) 
                             ...

【参考方案2】：

将代码中的 PHAsset *lastAsset=[fetchResult lastObject]; 替换为

PHAsset *lastAsset=fetchResult;