iOS开发之获取系统相册中的图片与视频(内带url转换)

#import <AssetsLibrary/AssetsLibrary.h>  // 必须导入

// 照片原图路径
#define KOriginalPhotoImagePath   
[[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) objectAtIndex:0] stringByAppendingPathComponent:@"OriginalPhotoImages"]

// 视频URL路径
#define KVideoUrlPath   
[[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) objectAtIndex:0] stringByAppendingPathComponent:@"VideoURL"]

// caches路径
#define KCachesPath   
[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) objectAtIndex:0]

// MainViewController
@interface MTHMainViewController ()

@property (nonatomic,strong) MTHNextViewController *nextVC;
@property (nonatomic,strong) NSMutableArray        *groupArrays;
@property (nonatomic,strong) UIImageView           *litimgView;

@end

@implementation MTHMainViewController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    self.navigationItem.title = @"Demo";
    self.view.backgroundColor = [UIColor clearColor];
    
    // 初始化
    self.groupArrays = [NSMutableArray array];
    
    // 测试BarItem
    self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"测试" style:UIBarButtonItemStylePlain target:self action:@selector(testRun)];
    
    // 测试手势
    UIPanGestureRecognizer *panRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(didClickPanGestureRecognizer:)];
    [self.navigationController.view addGestureRecognizer:panRecognizer];
    
    // 图片或者视频的缩略图显示
    self.litimgView = [[UIImageView alloc] initWithFrame:CGRectMake(100, 200, 120, 120)];
    [self.view addSubview:_litimgView];
}


- (void)testRun
{
    __weak MTHMainViewController *weakSelf = self;
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        ALAssetsLibraryGroupsEnumerationResultsBlock listGroupBlock = ^(ALAssetsGroup *group, BOOL *stop) {
            if (group != nil) {
                [weakSelf.groupArrays addObject:group];
            } else {
                [weakSelf.groupArrays enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
                    [obj enumerateAssetsUsingBlock:^(ALAsset *result, NSUInteger index, BOOL *stop) {
                        if ([result thumbnail] != nil) {
                            // 照片
                            if ([[result valueForProperty:ALAssetPropertyType] isEqualToString:ALAssetTypePhoto]){
                                
                                NSDate *date= [result valueForProperty:ALAssetPropertyDate];
                                UIImage *image = [UIImage imageWithCGImage:[result thumbnail]];
                                NSString *fileName = [[result defaultRepresentation] filename];
                                NSURL *url = [[result defaultRepresentation] url];
                                int64_t fileSize = [[result defaultRepresentation] 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(), ^{
                                    self.litimgView.image = image;
                                });
                            }
                            // 视频
                            else if ([[result valueForProperty:ALAssetPropertyType] isEqualToString:ALAssetTypeVideo] ){
                            
                                // 和图片方法类似
                            }
                        }
                    }];
                }];

            }
        };
        
        ALAssetsLibraryAccessFailureBlock failureBlock = ^(NSError *error)
        {
            
            NSString *errorMessage = nil;
            
            switch ([error code]) {
                case ALAssetsLibraryAccessUserDeniedError:
                case ALAssetsLibraryAccessGloballyDeniedError:
                    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 = [[UIAlertView alloc]initWithTitle:@"错误,无法访问!"
                                                                   message:errorMessage
                                                                  delegate:self
                                                         cancelButtonTitle:@"确定"
                                                         otherButtonTitles:nil, nil];
                [alertView show];
            });
        };
        
        
        ALAssetsLibrary *assetsLibrary = [[ALAssetsLibrary alloc]  init];
        [assetsLibrary enumerateGroupsWithTypes:ALAssetsGroupAll
                                     usingBlock:listGroupBlock failureBlock:failureBlock];
    });
}

按照上面方法直接取出来的路径是无法传输的,必须自己转化成NSData对象重新写入沙盒路径

// 将原始图片的URL转化为NSData数据,写入沙盒
- (void)imageWithUrl:(NSURL *)url withFileName:(NSString *)fileName
{
    // 进这个方法的时候也应该加判断,如果已经转化了的就不要调用这个方法了
    // 如何判断已经转化了,通过是否存在文件路径
    ALAssetsLibrary *assetLibrary = [[ALAssetsLibrary alloc] init];
    // 创建存放原始图的文件夹--->OriginalPhotoImages
    NSFileManager * fileManager = [NSFileManager defaultManager];
    if (![fileManager fileExistsAtPath:KOriginalPhotoImagePath]) {
        [fileManager createDirectoryAtPath:KOriginalPhotoImagePath withIntermediateDirectories:YES attributes:nil error:nil];
    }
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        if (url) {
            // 主要方法
            [assetLibrary assetForURL:url resultBlock:^(ALAsset *asset) {
                ALAssetRepresentation *rep = [asset defaultRepresentation];
                Byte *buffer = (Byte*)malloc((unsigned long)rep.size);
                NSUInteger buffered = [rep getBytes:buffer fromOffset:0.0 length:((unsigned long)rep.size) error:nil];
                NSData *data = [NSData dataWithBytesNoCopy:buffer length:buffered freeWhenDone:YES];
                NSString * imagePath = [KOriginalPhotoImagePath stringByAppendingPathComponent:fileName];
                [data writeToFile:imagePath atomically:YES];
            } failureBlock:nil];
        }
    });
}

// 将原始视频的URL转化为NSData数据,写入沙盒
- (void)videoWithUrl:(NSURL *)url withFileName:(NSString *)fileName
{
    // 解析一下,为什么视频不像图片一样一次性开辟本身大小的内存写入?
    // 想想,如果1个视频有1G多,难道直接开辟1G多的空间大小来写?
    ALAssetsLibrary *assetLibrary = [[ALAssetsLibrary alloc] init];
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        if (url) {
            [assetLibrary assetForURL:url resultBlock:^(ALAsset *asset) {
                ALAssetRepresentation *rep = [asset defaultRepresentation];
                NSString * videoPath = [KCachesPath stringByAppendingPathComponent:fileName];
                char const *cvideoPath = [videoPath UTF8String];
                FILE *file = fopen(cvideoPath, "a+");
                if (file) {
                    const int bufferSize = 1024 * 1024;
                    // 初始化一个1M的buffer
                    Byte *buffer = (Byte*)malloc(bufferSize);
                    NSUInteger read = 0, offset = 0, written = 0;
                    NSError* err = nil;
                    if (rep.size != 0)
                    {
                        do {
                            read = [rep getBytes:buffer fromOffset:offset length:bufferSize error:&err];
                            written = fwrite(buffer, sizeof(char), read, file);
                            offset += read;
                        } while (read != 0 && !err);//没到结尾，没出错，ok继续
                    }
                    // 释放缓冲区，关闭文件
                    free(buffer);
                    buffer = NULL;
                    fclose(file);
                    file = NULL;
                }
            } failureBlock:nil];
        }
    });
}