iOS开发——系统相册操作

在我们的应用中使用图片、视频，尤其是大量的图片、视频的时候。如果存储在沙盒中，会使得该应用的沙盒文件越来越大。所以，一些图片、视频资源可以放到系统相册中保存。这样也有利于用户查看该类资源。

但是，资源存储在了系统相册，我们对其的访问就受到了一定的限制。具体解决办法如下：

1.把视频、图片存储在系统相册：

ALAssetsLibrary *library = [[ALAssetsLibraryalloc]init];

视频存储：- (void)writeVideoAtPathToSavedPhotosAlbum:(NSURL *)videoPathURL completionBlock:(ALAssetsLibraryWriteVideoCompletionBlock)completionBlock;

图片存储：- (void)writeImageDataToSavedPhotosAlbum:(NSData *)imageData metadata:(NSDictionary *)metadata completionBlock:(ALAssetsLibraryWriteImageCompletionBlock)completionBlock 

2.把图片、视频文件从相册中读取出来：

- (void)getThumImageAndURLForPhotoAndVideo
{
    __weakXYLocalAlbumViewcontroller *weakSelf =self;
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT,0), ^{
        ALAssetsLibraryGroupsEnumerationResultsBlock listGroupBlock = ^(ALAssetsGroup *group, BOOL *stop) {
            if (group !=nil) {
                [weakSelf.groupArraysaddObject:group];
                NSLog(@"[group valueForProperty:ALAssetsGroupPropertyName]: %@",[group valueForProperty:ALAssetsGroupPropertyName]);
                if ([[groupvalueForProperty:ALAssetsGroupPropertyName]isEqualToString:XIAOYIALBUM]) {
                    self.collectionViewCellCount = group.numberOfAssets;
                    NSLog(@"self.collectionViewCellCount: %ld",self.collectionViewCellCount);
                   

                    // UI的更新记得放在主线程

                    dispatch_async(dispatch_get_main_queue(), ^{
                        [selfcreateCollectionViewForAlbum];
                    });
                }
            } else {
                [weakSelf.groupArraysenumerateObjectsUsingBlock:^(id obj, NSUInteger idx,BOOL *stop) {
                    NSLog(@"obj----idx: %@---------%lu",obj, (unsignedlong)idx);
                    if ([[(ALAssetsGroup *)obj valueForProperty:ALAssetsGroupPropertyName]isEqualToString:XIAOYIALBUM]) {
                        [obj enumerateAssetsUsingBlock:^(ALAsset *result, NSUInteger index,BOOL *stop) {
                            if ([resultthumbnail] !=nil) {
                                //照片
                                if ([[resultvalueForProperty:ALAssetPropertyType]isEqualToString:ALAssetTypePhoto]){
                                   
                                    NSDate *date= [resultvalueForProperty:ALAssetPropertyDate];
                                    //                                UIImage *image = [UIImage imageWithCGImage:[result thumbnail]];
                                    NSString *fileName = [[resultdefaultRepresentation]filename];
                                    NSURL *url = [[resultdefaultRepresentation]url];
                                    int64_t fileSize = [[resultdefaultRepresentation]size];
                                   
                                    NSLog(@"date = %@",date);
                                    NSLog(@"fileName = %@",fileName);
                                    NSLog(@"url = %@",url);
                                    NSLog(@"fileSize = %lld",fileSize);
                                   
                                    // UI的更新记得放在主线程,要不然等子线程排队过来都不知道什么年代了,会很慢的
                                    dispatch_async(dispatch_get_main_queue(), ^{
                                       
                                    });
                                }
                                //视频
                                elseif ([[resultvalueForProperty:ALAssetPropertyType]isEqualToString:ALAssetTypeVideo] ){
                                   
                                    //和图片方法类似
                                    NSDate *date= [resultvalueForProperty:ALAssetPropertyDate];
                                    //                                UIImage *image = [UIImage imageWithCGImage:[result thumbnail]];
                                    NSString *fileName = [[resultdefaultRepresentation]filename];
                                    NSURL *url = [[resultdefaultRepresentation]url];
                                    int64_t fileSize = [[resultdefaultRepresentation]size];
                                   
                                    NSLog(@"date = %@",date);
                                    NSLog(@"fileName = %@",fileName);
                                    NSLog(@"url = %@",url);
                                    NSLog(@"fileSize = %lld",fileSize);
                                }
                            }
                        }];
                    }
                  
                }];
               
            }
        };
       
        ALAssetsLibraryAccessFailureBlock failureBlock = ^(NSError *error)
        {
           
            NSString *errorMessage =nil;
           
            switch ([errorcode]) {
                caseALAssetsLibraryAccessUserDeniedError:
                caseALAssetsLibraryAccessGloballyDeniedError:
                    errorMessage = @"用户拒绝访问相册,请在<隐私>中开启";
                    break;
                   
                default:
                    errorMessage = @"Reason unknown.";
                    break;
            }
           
            dispatch_async(dispatch_get_main_queue(), ^{
                UIAlertView *alertView = [[UIAlertViewalloc]initWithTitle:@"错误,无法访问!"
                                                                   message:errorMessage
                                                                  delegate:self
                                                         cancelButtonTitle:@"确定"
                                                         otherButtonTitles:nil,nil];
                [alertView show];
            });
        };
       
       
        ALAssetsLibrary *assetsLibrary = [[ALAssetsLibraryalloc] init];
        [assetsLibrary enumerateGroupsWithTypes:ALAssetsGroupAll
                                     usingBlock:listGroupBlockfailureBlock:failureBlock];
    });

}

//获取图片、视频的缩略图

- (void)getThumbnail

{

    ALAssetsLibrary *assetLibrary = [[ALAssetsLibraryalloc]init];

    for (int i = 0 ; i <self.dataArray.count; i++) {
        //获取路径
        NSString *string =self.dataArray[i];
        NSURL *url = [NSURLURLWithString:string];
        //根据图片url获取图片
        [assetLibrary assetForURL:urlresultBlock:^(ALAsset *asset) {

            if (asset != nil) {

                //缩略图img

                UIImage *image = [UIImageimageWithCGImage:asset.thumbnail];
                //
                if (image !=nil) {
                    [self.imagesArrayaddObject:image];
                   
                    //大图不需要
                   
                    //判断文件后缀,是图片还是视频,放到数组中,只有mp4格式被认为是视频
                    NSRange range = [stringrangeOfString:@"&ext="];
                    NSInteger loc = range.location + range.length;
                    NSString *subString = [stringsubstringFromIndex:loc];
                    NSString *suffix =nil;
                    if ([subStringisEqualToString:@"mp4"]) {
                        suffix = @"mp4";
                    } else {
                        suffix = @"notMp4";
                    }
                    [self.photoOrVideoArrayaddObject:suffix];
                   
                    [self.imageDictsetObject:imageforKey:string];

                    [self.typeDictsetObject:suffixforKey:string];

                }
            }


        } failureBlock:^(NSError *error) {

            

        }];
       

    }

}

除了删除操作，其他的操作基本都有了。