一. 相册内数据转沙盒应用场景

• 使用ReplayKit时,需要将保存到相册的视频上传至服务器,这时需要把相册的数据转换到沙盒中.

二. Photos库--从相册取最近一次的图片/视频复制一份到沙盒

• 注意: ALAssetLibrary在ios8已经过期,操作相册苹果推荐用更新的Photos类库,此处使用Photos类库讲解,ALAssetLibrary不再阐述.
• 访问相册需要提前获取相册权限,修改权限会重启应用

基本思路

• PHAsset 对象能获取图片相关的信息,非图片本身.
• 相册和沙盒都在一个文件系统中,所以不需要把相册图片/视频全部加载到内存中(会导致内存暴增)再存储
• 使用PHAssetResource和PHAssetResourceManager就可以直接复制图片/视频到沙盒中,不会导致内存暴增.
• 使用assetResourcesForAsset:方法可以把PHAsset转化为PHAssetResource

1.判断相册权限

AVAuthorizationStatus authStatus = [AVCaptureDevice authorizationStatusForMediaType:AVMediaTypeVideo];
    if (authStatus == AVAuthorizationStatusRestricted || authStatus ==AVAuthorizationStatusDenied)
    {
        MLNewCustomDialog *ncd=[[MLNewCustomDialog alloc] initWithTitle:@"温馨提示" andMoreText:@"请您设置允许本应用访问您的相机\n设置>隐私>相机" andButton1:@"好的" andButton2:nil andBackViewForBlurImage:self.view];
        ncd.delegate=self;
        [self.view addSubview:ncd];
        [ncd show];
        return ;
    }

2.拷贝相册中最近一次的图片/视频到沙盒中,方便上传到服务器.

#import <Photos/Photos.h>

- (void)saveVideoSuccess:(void(^)())success{
    //获取最近一次的相册图片/视频的信息PHAsset
    PHFetchOptions *options = [[PHFetchOptions alloc] init];
    options.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"creationDate" ascending:NO]];
    options.includeAssetSourceTypes = PHAssetSourceTypeNone;//默认相册
    PHFetchResult *assetsFetchResults = [PHAsset fetchAssetsWithOptions:options];
    PHAsset *asset = [assetsFetchResults firstObject];
    PHAssetResource *assetRescource = [[PHAssetResource assetResourcesForAsset:asset] firstObject];

    //创建保存到沙盒的路径
    NSString *uuidString = [[NSUUID UUID] UUIDString];
    NSString *fileName = uuidString;
    NSString *documentPath = [NSString stringWithFormat:@"%@/photosFile", [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) firstObject]];
    NSFileManager *fileManager = [NSFileManager defaultManager];
    BOOL isDir= NO;
    BOOL existed = [fileManager fileExistsAtPath:documentPath isDirectory:&isDir];
    if (!(existed&&isDir)){
        [fileManager createDirectoryAtPath:documentPath withIntermediateDirectories:YES attributes:nil error:nil];
    }
    NSString *filePath=[documentPath stringByAppendingPathComponent:fileName];

    //保存到沙盒
     __weak typeof(self) weakSelf = self;
    PHAssetResourceManager *manager = [PHAssetResourceManager defaultManager];
    [manager writeDataForAssetResource:assetRescource toFile:[NSURL fileURLWithPath:filePath] options:nil completionHandler:^(NSError * _Nullable error) {
        if (error==nil) {
            if(success)success();
            NSLog(@"保存沙盒成功");
            [self showStudentAndTeacherView];
        }else{
            [weakSelf saveVideoSuccess:success];
            NSLog(@"保存沙盒失败,重新尝试");
        }
    }];
}

• 附相关博文推荐
  iOS 开发之照片框架详解之二 —— PhotoKit 详解
  http://kayosite.com/ios-development-and-detail-of-photo-framework-part-two.html
  Photos框架之获取系统所有相册与照片
  http://blog.imerc.xyz/2016/12/12/photokit-get-all-albums-and-photos/
  Photos框架之视频相关
  http://blog.imerc.xyz/2017/01/31/photokit-video/

作者：Jesscia_Liu
链接：https://www.jianshu.com/p/e63ae8d90c3a
来源：简书
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