关于ALAssetsLibrary的学习

添加AssetsLibrary.framework
然后引入

#import <AssetsLibrary/ALAssetsLibrary.h>

一个获取所有图片的类

.h

#import <UIKit/UIKit.h>

#include<AssetsLibrary/AssetsLibrary.h>

@interface ViewController :UIViewController{

    ALAssetsLibrary *library; 

   NSArray *imageArray;

   NSMutableArray *mutableArray;

}

-(void)allPhotosCollected:(NSArray*)imgArray;

@end

.m

#import "ViewController.h"

@interface ViewController ()

@end

staticint count=0;

@implementation ViewController

- (void)viewDidLoad

{

   [super viewDidLoad];

    [selfgetAllPictures];

}

//获取所有图片

-(void)getAllPictures

{

   imageArray=[[NSArray alloc] init];

   mutableArray =[[NSMutableArray alloc]init];

    NSMutableArray* assetURLDictionaries = [[NSMutableArrayalloc] init];

   library = [[ALAssetsLibrary alloc] init];

   void (^assetEnumerator)( ALAsset *, NSUInteger, BOOLBOOL *) = ^(ALAsset *result, NSUInteger index, BOOLBOOL *stop) {

       if(result != nil) {

           if([[result valueForProperty:ALAssetPropertyType] isEqualToString:ALAssetTypePhoto]) {

               [assetURLDictionaries addObject:[result valueForProperty:ALAssetPropertyURLs]];

               NSURL *url= (NSURL*) [[result defaultRepresentation]url];

                [library assetForURL:url resultBlock:^(ALAsset *asset) {

                           [mutableArray addObject:[UIImage imageWithCGImage:[[asset defaultRepresentation] fullScreenImage]]];

                            if ([mutableArray count]==count)

                             {                              

                                 imageArray=[[NSArray alloc] initWithArray:mutableArray];                             

                                 [self allPhotosCollected:imageArray];            

                             }                           

                        }

                       failureBlock:^(NSError *error){ NSLog(@"operation was not successfull!"); } ];

           }         

        }  

   }; 

    NSMutableArray *assetGroups = [[NSMutableArrayalloc] init];

   void (^ assetGroupEnumerator) ( ALAssetsGroup *, BOOLBOOL *)= ^(ALAssetsGroup *group, BOOLBOOL *stop) {   

       if(group != nil) {   

           [group enumerateAssetsUsingBlock:assetEnumerator];

           [assetGroups addObject:group];

            count=[group numberOfAssets]; 

       }    

   };

   assetGroups = [[NSMutableArrayalloc] init];

    [library enumerateGroupsWithTypes:ALAssetsGroupAll usingBlock:assetGroupEnumerator failureBlock:^(NSError *error) {

     NSLog(@"There is an error");}];  

}

-(void)allPhotosCollected:(NSArray*)imgArray

{

    //write your code here after getting all the photos from library...

    NSLog(@"all pictures are %@",imgArray);

}

@end

以下是关于AssetsLibrary的一些方法说明，仅供参考

//初始化，这个简单

if (!self.assetsLibrary) {

    _assetsLibrary = [[ALAssetsLibrary alloc] init];

}

//添加一个group，成功后查看一些信息

[_assetsLibrary addAssetsGroupAlbumWithName:@"tesddt" resultBlock:^(ALAssetsGroup *group) {

   //查看相册的名字

    NSLog(@"ALAssetsGroupPropertyName:%@",[group valueForProperty:ALAssetsGroupPropertyName]);

   //查看相册的类型

    NSLog(@"ALAssetsGroupPropertyType:%@",[group valueForProperty:ALAssetsGroupPropertyType]);

    //查看相册的存储id

    NSLog(@"ALAssetsGroupPropertyPersistentID:%@",[group valueForProperty:ALAssetsGroupPropertyPersistentID]);

   //查看相册存储的位置地址

    NSLog(@"ALAssetsGroupPropertyURL:%@",[group valueForProperty:ALAssetsGroupPropertyURL]);

} failureBlock:^(NSError *error) {

    

}];

可以通过valueForProperty获取到图片的信息，包括类型， Location , 时长，方向，日期，格式 ， URL地址。
NSString * nsALAssetPropertyType = [ asset valueForProperty:ALAssetPropertyType ] ;
NSString * nsALAssetPropertyLocation = [ asset valueForProperty:ALAssetPropertyLocation ] ;
NSString * nsALAssetPropertyDuration = [ asset valueForProperty:ALAssetPropertyDuration ] ;
NSString * nsALAssetPropertyOrientation = [ asset valueForProperty:ALAssetPropertyOrientation ] ;
NSString * nsALAssetPropertyDate = [ asset valueForProperty:ALAssetPropertyDate ] ;
NSString * nsALAssetPropertyRepresentations = [ asset valueForProperty:ALAssetPropertyRepresentations ] ;
NSString * nsALAssetPropertyURLs = [ asset valueForProperty:ALAssetPropertyURLs ] ;
NSString * nsALAssetPropertyAssetURL = [ asset valueForProperty:ALAssetPropertyAssetURL ] ;

//通过url地址在相册资源中获取该地址的资源文件ALAsset，有可能是相片或视频

[_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;

   //查看资源的地理位置信息

    NSLog(@"ALAssetPropertyLocation:%@",[asset valueForProperty:ALAssetPropertyLocation]);

   //如果资源是视频，查看视频的时长

    NSLog(@"ALAssetPropertyDuration:%@",[asset valueForProperty:ALAssetPropertyDuration]);

   //查看资源的方向，图片的旋转方向

    NSLog(@"ALAssetPropertyOrientation:%@",[asset valueForProperty:ALAssetPropertyOrientation]);

   //查看资源的创建时间

    NSLog(@"ALAssetPropertyDate:%@",[asset valueForProperty:ALAssetPropertyDate]);

   //查看资源的描述信息

    NSLog(@"ALAssetPropertyRepresentations:%@",[asset valueForProperty:ALAssetPropertyRepresentations]);

    NSLog(@"ALAssetPropertyURLs:%@",[asset valueForProperty:ALAssetPropertyURLs]);

    //查看资源的url路径

    NSLog(@"ALAssetPropertyAssetURL:%@",[asset valueForProperty:ALAssetPropertyAssetURL]);

} failureBlock:^(NSError *error) {

}];

//通过url地址获取相册资源中的一个相册

[_library groupForURL:groupURL resultBlock:^(ALAssetsGroup *group) {

    NSLog(@"ALAssetsGroupPropertyName:%@",[group valueForProperty:ALAssetsGroupPropertyName]);

} failureBlock:^(NSError *error) {

    

}];

//根据选择的类型遍历相册资源中的相对应类型的所有相册，其中stop行参是指针，表示是否停止迭代，当赋值为false则停止

//        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, BOOLBOOL *stop) {

    NSLog(@"group name:%@",[group valueForProperty:ALAssetsGroupPropertyName]);

} failureBlock:^(NSError *error) {

    

}];

//保存图片到系统默认的相册中，使用cgimageref的形式，并返回照片的url地址

[_library writeImageToSavedPhotosAlbum:nil metadata:nil completionBlock:^(NSURL *assetURL, NSError *error) {

    

}];

//保存图片到系统默认的相册中，使用cgimageref的形式，并且选择图片以什么旋转方向的形式保存，并返回照片的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 = [UIImageimageNamed:@"test.png"];

[_library writeImageToSavedPhotosAlbum:[image CGImage] orientation:ALAssetOrientationLeft completionBlock:^(NSURL *assetURL, NSError *error) {

    NSLog(@"save image:%@",assetURL);

}];