ALAssetsLibrary詳解

ALAssetsLibrary類是表明系統中整個資源庫，使用它能夠訪問資源庫中的資源和保存照片，視頻等功能。

    _library = [[ALAssetsLibrary alloc]init];
    //判斷當前應用是否能訪問相冊資源
    /*
     typedef NS_ENUM(NSInteger, ALAuthorizationStatus) {
     ALAuthorizationStatusNotDetermined = 0, 用戶還沒有作出了選擇這個應用程序的問候
     ALAuthorizationStatusRestricted,        此應用程序沒有被受權訪問的照片數據。多是家長控制權限。

     ALAuthorizationStatusDenied,            用戶已經明確否定了這一照片數據的應用程序訪問.
     ALAuthorizationStatusAuthorized         用戶已受權應用訪問照片數據.
     }
     */
    int author = [ALAssetsLibrary authorizationStatus];
    NSLog(@"author type:%d",author);
    //關閉監聽共享照片流產生的頻繁通知信息
    [ALAssetsLibrary disableSharedPhotoStreamsSupport];
    
    //建立一個相冊到相冊資源中，並經過block返回建立成功的相冊ALAssetsGroup
    [_library addAssetsGroupAlbumWithName:@"test" resultBlock:^(ALAssetsGroup *group) {
        //NSString *const ALAssetsGroupPropertyName;
        //NSString *const ALAssetsGroupPropertyType;
        //NSString *const ALAssetsGroupPropertyPersistentID;
        //NSString *const ALAssetsGroupPropertyURL;
        //查看相冊的名字
        NSLog(@"ALAssetsGroupPropertyName:%@",[group valueForProperty:ALAssetsGroupPropertyName]);
        //查看相冊的類型
        NSLog(@"ALAssetsGroupPropertyType:%@",[group valueForProperty:ALAssetsGroupPropertyType]);
        //查看相冊的存儲id
        NSLog(@"ALAssetsGroupPropertyPersistentID:%@",[group valueForProperty:ALAssetsGroupPropertyPersistentID]);
        //查看相冊存儲的位置地址
        NSLog(@"ALAssetsGroupPropertyURL:%@",[group valueForProperty:ALAssetsGroupPropertyURL]);
        groupURL = [group valueForProperty:ALAssetsGroupPropertyURL];

    } failureBlock:^(NSError *error) {
        
    }];

新添加了一個名爲test的相冊

    [NSThread sleepForTimeInterval:0.5];
    //經過url地址在相冊資源中獲取該地址的資源文件ALAsset，有多是相片或視頻
    [_library assetForURL:[NSURL URLWithString:@""] resultBlock:^(ALAsset *asset) {
        /*
         NSString *const ALAssetPropertyType;
         NSString *const ALAssetPropertyLocation;
         NSString *const ALAssetPropertyDuration;
         NSString *const ALAssetPropertyOrientation;
         NSString *const ALAssetPropertyDate;
         NSString *const ALAssetPropertyRepresentations;
         NSString *const ALAssetPropertyURLs;
         NSString *const ALAssetPropertyAssetURL;
         */
        //查看資源的地理位置信息
        NSLog(@"ALAssetPropertyLocation:%@",[asset valueForProperty:ALAssetPropertyLocation]);
        //若是資源是視頻，查看視頻的時長
        NSLog(@"ALAssetPropertyDuration:%@",[asset valueForProperty:ALAssetPropertyDuration]);
        //查看資源的方向，圖片的旋轉方向
        NSLog(@"ALAssetPropertyOrientation:%@",[asset valueForProperty:ALAssetPropertyOrientation]);
        //查看資源的建立時間
        NSLog(@"ALAssetPropertyDate:%@",[asset valueForProperty:ALAssetPropertyDate]);
        //查看資源的描述信息
        NSLog(@"ALAssetPropertyRepresentations:%@",[asset valueForProperty:ALAssetPropertyRepresentations]);
        NSLog(@"ALAssetPropertyURLs:%@",[asset valueForProperty:ALAssetPropertyURLs]);
        //查看資源的url路徑
        NSLog(@"ALAssetPropertyAssetURL:%@",[asset valueForProperty:ALAssetPropertyAssetURL]);
    } failureBlock:^(NSError *error) {
        
    }];
    //經過url地址獲取相冊資源中的一個相冊
    [_library groupForURL:groupURL resultBlock:^(ALAssetsGroup *group) {
        NSLog(@"ALAssetsGroupPropertyName:%@",[group valueForProperty:ALAssetsGroupPropertyName]);
    } failureBlock:^(NSError *error) {
    
    }];
    //根據選擇的類型遍歷相冊資源中的相對應類型的全部相冊，其中stop行參是指針，表示是否中止迭代，當賦值爲false則中止
    /*
     enum {
     ALAssetsGroupLibrary        = (1 << 0),
     ALAssetsGroupAlbum          = (1 << 1),
     ALAssetsGroupEvent          = (1 << 2),
     ALAssetsGroupFaces          = (1 << 3),
     ALAssetsGroupSavedPhotos    = (1 << 4),
     ALAssetsGroupPhotoStream    = (1 << 5),
     ALAssetsGroupAll            = 0xFFFFFFFF,
     };
     */
    [_library enumerateGroupsWithTypes:ALAssetsGroupAll usingBlock:^(ALAssetsGroup *group, BOOL *stop) {
        NSLog(@"group name:%@",[group valueForProperty:ALAssetsGroupPropertyName]);
    } failureBlock:^(NSError *error) {
        
    }];
    //保存圖片到系統默認的相冊中，使用nsdata的形式，並返回照片的url地址
    [_library writeImageDataToSavedPhotosAlbum:nil metadata:nil completionBlock:^(NSURL *assetURL, NSError *error) {
        
    }];
    //保存圖片到系統默認的相冊中，使用cgimageref的形式，並返回照片的url地址
    [_library writeImageToSavedPhotosAlbum:nil metadata:nil completionBlock:^(NSURL *assetURL, NSError *error) {
        
    }];
    
    //保存圖片到系統默認的相冊中，使用cgimageref的形式，而且選擇圖片以什麼旋轉方向的形式保存，並返回照片的url地址
    /*
     typedef enum {
     ALAssetOrientationUp,            // default orientation
     ALAssetOrientationDown,          // 180 deg rotation
     ALAssetOrientationLeft,          // 90 deg CCW
     ALAssetOrientationRight,         // 90 deg CW
     ALAssetOrientationUpMirrored,    // as above but image mirrored along other axis. horizontal flip
     ALAssetOrientationDownMirrored,  // horizontal flip
     ALAssetOrientationLeftMirrored,  // vertical flip
     ALAssetOrientationRightMirrored, // vertical flip
     } ALAssetOrientation;
     */
    UIImage* image = [UIImage imageNamed:@"test.png"];
    [_library writeImageToSavedPhotosAlbum:[image CGImage] orientation:ALAssetOrientationLeft completionBlock:^(NSURL *assetURL, NSError *error) {
        NSLog(@"save image:%@",assetURL);
    }];