好些天沒寫點東西了，最近公司要做新項目，有點小忙。不想我的堅持就此中斷，我把我前些天研究的東西拿出來給大家看看。
這次整理的是AssetsLibrary和PhotoKit的使用。本人處女座，有點強迫癥，之前寫的項目里用的是AssetsLibrary寫的調取相冊內的媒體文件，但是Xcode總是報警告錯誤，雖然能夠編譯并展示效果，但是十幾個警告錯誤掛在那，心里總不是滋味，所以我就研究了一下AssetLibrary和PhotoKit。
在 iOS 8 出現(xiàn)之前，開發(fā)者只能使用 AssetsLibrary 框架來訪問設備的照片庫，這是一個有點跟不上 iOS 應用發(fā)展步伐以及代碼設計原則但確實強大的框架，考慮到 iOS7 仍占有不少的滲透率，因此 AssetsLibrary 也是本文重點介紹的部分。而在 iOS8 出現(xiàn)之后，蘋果提供了一個名為 PhotoKit 的框架，一個可以讓應用更好地與設備照片庫對接的框架。
一、AssetsLibrary 組成
AssetsLibrary 的組成比較符合照片庫本身的組成，照片庫中的完整照片庫對象、相冊、相片都能在 AssetsLibrary 中找到一一對應的組成，這使到 AssetsLibrary 的使用變得直觀而方便。想要了解AssetsLibrary得從它的類開始。
AssetsLibrary: 代表整個設備中的資源庫（照片庫），通過 AssetsLibrary 可以獲取和包括設備中的照片和視頻
@話不多說,直接上代碼
#import <AssetsLibrary/AssetsLibrary.h> // 必須導入 // 照片原圖路徑 #define KOriginalPhotoImagePath / [[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) objectAtIndex:0] stringByAppendingPathComponent:@"OriginalPhotoImages"] // 視頻URL路徑 #define KVideoUrlPath / [[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) objectAtIndex:0] stringByAppendingPathComponent:@"VideoURL"] // caches路徑 #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]; // 測試BarItem self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"測試" style:UIBarButtonItemStylePlain target:self action:@selector(testRun)]; // 測試手勢 UIPanGestureRecognizer *panRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(didClickPanGestureRecognizer:)]; [self.navigationController.view addGestureRecognizer:panRecognizer]; // 圖片或者視頻的縮略圖顯示 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, BOOLBOOL *stop) { if (group != nil) { [weakSelf.groupArrays addObject:group]; } else { [weakSelf.groupArrays enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOLBOOL *stop) { [obj enumerateAssetsUsingBlock:^(ALAsset *result, NSUInteger index, BOOLBOOL *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的更新記得放在主線程,要不然等子線程排隊過來都不知道什么年代了,會很慢的 dispatch_async(dispatch_get_main_queue(), ^{ self.litimgView.image = image; }); } // 視頻 else if ([[result valueForProperty:ALAssetPropertyType] isEqualToString:ALAssetTypeVideo] ){ // 和圖片方法類似 } } }]; }]; } }; ALAssetsLibraryAccessFailureBlock failureBlock = ^(NSError *error) { NSString *errorMessage = nil; switch ([error code]) { case ALAssetsLibraryAccessUserDeniedError: case ALAssetsLibraryAccessGloballyDeniedError: errorMessage = @"用戶拒絕訪問相冊,請在<隱私>中開啟"; break; default: errorMessage = @"Reason unknown."; break; } dispatch_async(dispatch_get_main_queue(), ^{ UIAlertView *alertView = [[UIAlertView alloc]initWithTitle:@"錯誤,無法訪問!" message:errorMessage delegate:self cancelButtonTitle:@"確定" otherButtonTitles:nil, nil nil]; [alertView show]; }); }; ALAssetsLibrary *assetsLibrary = [[ALAssetsLibrary alloc] init]; [assetsLibrary enumerateGroupsWithTypes:ALAssetsGroupAll usingBlock:listGroupBlock failureBlock:failureBlock]; }); } 
@但是:
按照上面方法直接取出來的路徑是無法傳輸?shù)?必須自己轉化成NSData對象重新寫入沙盒路徑
// 將原始圖片的URL轉化為NSData數(shù)據(jù),寫入沙盒 - (void)imageWithUrl:(NSURL *)url withFileName:(NSString *)fileName { // 進這個方法的時候也應該加判斷,如果已經(jīng)轉化了的就不要調用這個方法了 // 如何判斷已經(jīng)轉化了,通過是否存在文件路徑 ALAssetsLibrary *assetLibrary = [[ALAssetsLibrary alloc] init]; // 創(chuàng)建存放原始圖的文件夾--->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]; } }); } // 將原始視頻的URL轉化為NSData數(shù)據(jù),寫入沙盒 - (void)videoWithUrl:(NSURL *)url withFileName:(NSString *)fileName { // 解析一下,為什么視頻不像圖片一樣一次性開辟本身大小的內存寫入? // 想想,如果1個視頻有1G多,難道直接開辟1G多的空間大小來寫? 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 constconst *cvideoPath = [videoPath UTF8String]; FILEFILE *file = fopen(cvideoPath, "a+"); if (file) { const int bufferSize = 11024 * 1024; // 初始化一個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);//沒到結尾，沒出錯，ok繼續(xù) } // 釋放緩沖區(qū)，關閉文件 free(buffer); buffer = NULL; fclose(file); file = NULL; } } failureBlock:nil]; } }); } 以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持武林網(wǎng)。
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