通过自定义相册来介绍photo library的使用

　　因为我在模仿美图秀秀的功能，在使用相册时候，UIImagePickerController本来就是一个UINavigationController的子类，所以没有办法使用push，所以做了一个自定义的非UINavigationController子类的相册。使用的api是ios8以上提供的photokit。

　　一、获取相册的所有相册集

　　例如：个人收藏，最近添加，相机胶卷等。

　　1.使用+ (PHFetchResult<PHAssetCollection *> *)fetchAssetCollectionsWithType:(PHAssetCollectionType)type subtype:(PHAssetCollectionSubtype)subtype options:(nullable PHFetchOptions *)options方法来获取相册集集合

PHFetchResult返回了结果

　　2.使用+ (PHFetchResult<PHAsset *> *)fetchAssetsInAssetCollection:(PHAssetCollection *)assetCollection options:(nullable PHFetchOptions *)options方法来获取相册集内的所有照片资源

　　

- (PHFetchResult *)fetchAssetsInAssetCollection:(PHAssetCollection *)assetCollection ascending:(BOOL)ascending
{
    PHFetchOptions *options = [[PHFetchOptions alloc] init];
    options.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"creationDate" ascending:ascending]];
    PHFetchResult *result = [PHAsset fetchAssetsInAssetCollection:assetCollection options:options];
    
    return result;
}

- (NSArray <PHAsset *> *)getAssetsInAssetCollection:(PHAssetCollection *)assetCollection ascending:(BOOL)ascending
{
    NSMutableArray <PHAsset *> *mArr = [NSMutableArray array];
    PHFetchResult *result = [self fetchAssetsInAssetCollection:assetCollection ascending:ascending];
    [result enumerateObjectsUsingBlock:^(PHAsset *  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        if (obj.mediaType == PHAssetMediaTypeImage) {
            [mArr addObject:obj];
        }
    }];
    
    return mArr;
}

- (NSArray<PHAsset *> *)getAllAssetInPhotoAblumWithAscending:(BOOL)ascending
{
    NSMutableArray<PHAsset *> *assets = [NSMutableArray array];
    
    PHFetchOptions *option = [[PHFetchOptions alloc] init];
    
    option.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"creationDate" ascending:ascending]];
    
    PHFetchResult *result = [PHAsset fetchAssetsWithMediaType:PHAssetMediaTypeImage options:option];
    
    [result enumerateObjectsUsingBlock:^(PHAsset *  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        [assets addObject:obj];
    }];
    
    return assets;
}

- (NSArray <FWPhotoAlbums *> *)getPhotoAlbums
{
    NSMutableArray<FWPhotoAlbums *> *mArr = [NSMutableArray array];
    PHFetchResult *smartAlbum = [PHAssetCollection fetchAssetCollectionsWithType:PHAssetCollectionTypeSmartAlbum subtype:PHAssetCollectionSubtypeAlbumRegular options:nil];
    [smartAlbum enumerateObjectsUsingBlock:^(PHAssetCollection *  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        if (obj.assetCollectionSubtype != 202 && obj.assetCollectionSubtype < 212) {
            NSArray <PHAsset *> *assets = [self getAssetsInAssetCollection:obj ascending:NO];
            if ([assets count]) {
                FWPhotoAlbums *pa = [[FWPhotoAlbums alloc] init];
                pa.albumName = [self TitleOfAlbumForChinse:obj.localizedTitle];
                pa.albumImageCount = [assets count];
                pa.firstImageAsset = assets.firstObject;
                pa.assetCollection = obj;
                [mArr addObject:pa];
            }
        }
    }];
    
    PHFetchResult *userAlbums = [PHAssetCollection fetchAssetCollectionsWithType:PHAssetCollectionTypeAlbum subtype:PHAssetCollectionSubtypeSmartAlbumUserLibrary options:nil];
    [userAlbums enumerateObjectsUsingBlock:^(PHAssetCollection * _Nonnull collection, NSUInteger idx, BOOL * _Nonnull stop) {
        NSArray<PHAsset *> *assets = [self getAssetsInAssetCollection:collection ascending:YES];
        if (assets.count > 0) {
            FWPhotoAlbums *pa = [[FWPhotoAlbums alloc] init];
            pa.albumName = collection.localizedTitle;
            pa.albumImageCount = [assets count];
            pa.firstImageAsset = assets.firstObject;
            pa.assetCollection = collection;
            [mArr addObject:pa];
        }
    }];
    
    return mArr;
}

由于系统返回的相册集名称为英文，我们需要转换为中文

- (NSString *)TitleOfAlbumForChinse:(NSString *)title
{
    if ([title isEqualToString:@"Slo-mo"]) {
        return @"慢动作";
    } else if ([title isEqualToString:@"Recently Added"]) {
        return @"最近添加";
    } else if ([title isEqualToString:@"Favorites"]) {
        return @"个人收藏";
    } else if ([title isEqualToString:@"Recently Deleted"]) {
        return @"最近删除";
    } else if ([title isEqualToString:@"Videos"]) {
        return @"视频";
    } else if ([title isEqualToString:@"All Photos"]) {
        return @"所有照片";
    } else if ([title isEqualToString:@"Selfies"]) {
        return @"自拍";
    } else if ([title isEqualToString:@"Screenshots"]) {
        return @"屏幕快照";
    } else if ([title isEqualToString:@"Camera Roll"]) {
        return @"相机胶卷";
    }
    return nil;
}

二、获取照片

- (void)requestImageForAsset:(PHAsset *)asset size:(CGSize)size resizeMode:(PHImageRequestOptionsResizeMode)resizeMode completion:(void (^)(UIImage *, NSDictionary *))completion
{
    static PHImageRequestID requestID = -1;
    CGFloat scale = [UIScreen mainScreen].scale;
    CGFloat width = MIN(WIDTH, 800);
    if (requestID >= 1 && size.width/width==scale) {
        [[PHCachingImageManager defaultManager] cancelImageRequest:requestID];
    }
    
    PHImageRequestOptions *option = [[PHImageRequestOptions alloc] init];
    option.resizeMode = resizeMode;
    option.networkAccessAllowed = YES;
    
    requestID = [[PHCachingImageManager defaultManager] requestImageForAsset:asset targetSize:size contentMode:PHImageContentModeAspectFill options:option resultHandler:^(UIImage * _Nullable image, NSDictionary * _Nullable info) {
        BOOL downloadFinined = ![[info objectForKey:PHImageCancelledKey] boolValue] && ![info objectForKey:PHImageErrorKey];
        if (downloadFinined && completion) {
            completion(image, info);
        }
    }];
}

 三、拍照

  [_mCamera capturePhotoAsJPEGProcessedUpToFilter:_mFilter withCompletionHandler:^(NSData *processedJPEG, NSError *error){
        [[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
        [[PHAssetCreationRequest creationRequestForAsset] addResourceWithType:PHAssetResourceTypePhoto data:processedJPEG options:nil];
        } completionHandler:^(BOOL success, NSError * _Nullable error) {
            
        }];
    }];

效果

 　　　　　　

代码

1.模型类，存储相册集名称，相片数，第一张照片以及该相册集包含的所有照片集合

#import <Foundation/Foundation.h>
#import <photos/photos.h>

@interface FWPhotoAlbums : NSObject

@property (nonatomic, copy) NSString *albumName; //相册名字
@property (nonatomic, assign) NSUInteger albumImageCount; //该相册内相片数量
@property (nonatomic, strong) PHAsset *firstImageAsset; //相册第一张图片缩略图
@property (nonatomic, strong) PHAssetCollection *assetCollection; //相册集，通过该属性获取该相册集下所有照片

@end

#import "FWPhotoAlbums.h"

@implementation FWPhotoAlbums

@end

2.照片管理类，负责获取资源集合，请求照片

#import <Foundation/Foundation.h>
#import "FWPhotoAlbums.h"

@interface FWPhotoManager : NSObject

+ (instancetype)sharedManager;

- (NSArray <FWPhotoAlbums *> *)getPhotoAlbums;

- (NSArray<PHAsset *> *)getAllAssetInPhotoAblumWithAscending:(BOOL)ascending;

- (NSArray<PHAsset *> *)getAssetsInAssetCollection:(PHAssetCollection *)assetCollection ascending:(BOOL)ascending;

- (void)requestImageForAsset:(PHAsset *)asset size:(CGSize)size resizeMode:(PHImageRequestOptionsResizeMode)resizeMode completion:(void (^)(UIImage *image, NSDictionary *info))completion;

- (void)requestImageForAsset:(PHAsset *)asset scale:(CGFloat)scale resizeMode:(PHImageRequestOptionsResizeMode)resizeMode completion:(void (^)(UIImage *image))completion;

- (void)getPhotosBytesWithArray:(NSArray *)photos completion:(void (^)(NSString *photosBytes))completion;

- (BOOL)judgeAssetisInLocalAblum:(PHAsset *)asset ;
@end

#import "FWPhotoManager.h"

@implementation FWPhotoManager

+ (instancetype)sharedManager
{
    static FWPhotoManager *manager = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        manager = [[super allocWithZone:NULL] init];
    });
    
    return manager;
}

+ (instancetype)allocWithZone:(struct _NSZone *)zone
{
    return [self sharedManager];
}

- (PHFetchResult *)fetchAssetsInAssetCollection:(PHAssetCollection *)assetCollection ascending:(BOOL)ascending
{
    PHFetchOptions *options = [[PHFetchOptions alloc] init];
    options.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"creationDate" ascending:ascending]];
    PHFetchResult *result = [PHAsset fetchAssetsInAssetCollection:assetCollection options:options];
    
    return result;
}

- (NSArray <PHAsset *> *)getAssetsInAssetCollection:(PHAssetCollection *)assetCollection ascending:(BOOL)ascending
{
    NSMutableArray <PHAsset *> *mArr = [NSMutableArray array];
    PHFetchResult *result = [self fetchAssetsInAssetCollection:assetCollection ascending:ascending];
    [result enumerateObjectsUsingBlock:^(PHAsset *  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        if (obj.mediaType == PHAssetMediaTypeImage) {
            [mArr addObject:obj];
        }
    }];
    
    return mArr;
}

- (NSArray<PHAsset *> *)getAllAssetInPhotoAblumWithAscending:(BOOL)ascending
{
    NSMutableArray<PHAsset *> *assets = [NSMutableArray array];
    
    PHFetchOptions *option = [[PHFetchOptions alloc] init];
    
    option.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"creationDate" ascending:ascending]];
    
    PHFetchResult *result = [PHAsset fetchAssetsWithMediaType:PHAssetMediaTypeImage options:option];
    
    [result enumerateObjectsUsingBlock:^(PHAsset *  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        [assets addObject:obj];
    }];
    
    return assets;
}

- (NSArray <FWPhotoAlbums *> *)getPhotoAlbums
{
    NSMutableArray<FWPhotoAlbums *> *mArr = [NSMutableArray array];
    PHFetchResult *smartAlbum = [PHAssetCollection fetchAssetCollectionsWithType:PHAssetCollectionTypeSmartAlbum subtype:PHAssetCollectionSubtypeAlbumRegular options:nil];
    [smartAlbum enumerateObjectsUsingBlock:^(PHAssetCollection *  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        if (obj.assetCollectionSubtype != 202 && obj.assetCollectionSubtype < 212) {
            NSArray <PHAsset *> *assets = [self getAssetsInAssetCollection:obj ascending:NO];
            if ([assets count]) {
                FWPhotoAlbums *pa = [[FWPhotoAlbums alloc] init];
                pa.albumName = [self TitleOfAlbumForChinse:obj.localizedTitle];
                pa.albumImageCount = [assets count];
                pa.firstImageAsset = assets.firstObject;
                pa.assetCollection = obj;
                [mArr addObject:pa];
            }
        }
    }];
    
    PHFetchResult *userAlbums = [PHAssetCollection fetchAssetCollectionsWithType:PHAssetCollectionTypeAlbum subtype:PHAssetCollectionSubtypeSmartAlbumUserLibrary options:nil];
    [userAlbums enumerateObjectsUsingBlock:^(PHAssetCollection * _Nonnull collection, NSUInteger idx, BOOL * _Nonnull stop) {
        NSArray<PHAsset *> *assets = [self getAssetsInAssetCollection:collection ascending:YES];
        if (assets.count > 0) {
            FWPhotoAlbums *pa = [[FWPhotoAlbums alloc] init];
            pa.albumName = collection.localizedTitle;
            pa.albumImageCount = [assets count];
            pa.firstImageAsset = assets.firstObject;
            pa.assetCollection = collection;
            [mArr addObject:pa];
        }
    }];
    
    return mArr;
}

- (NSString *)TitleOfAlbumForChinse:(NSString *)title
{
    if ([title isEqualToString:@"Slo-mo"]) {
        return @"慢动作";
    } else if ([title isEqualToString:@"Recently Added"]) {
        return @"最近添加";
    } else if ([title isEqualToString:@"Favorites"]) {
        return @"个人收藏";
    } else if ([title isEqualToString:@"Recently Deleted"]) {
        return @"最近删除";
    } else if ([title isEqualToString:@"Videos"]) {
        return @"视频";
    } else if ([title isEqualToString:@"All Photos"]) {
        return @"所有照片";
    } else if ([title isEqualToString:@"Selfies"]) {
        return @"自拍";
    } else if ([title isEqualToString:@"Screenshots"]) {
        return @"屏幕快照";
    } else if ([title isEqualToString:@"Camera Roll"]) {
        return @"相机胶卷";
    }
    return nil;
}

- (void)requestImageForAsset:(PHAsset *)asset size:(CGSize)size resizeMode:(PHImageRequestOptionsResizeMode)resizeMode completion:(void (^)(UIImage *, NSDictionary *))completion
{
    static PHImageRequestID requestID = -1;
    CGFloat scale = [UIScreen mainScreen].scale;
    CGFloat width = MIN(WIDTH, 800);
    if (requestID >= 1 && size.width/width==scale) {
        [[PHCachingImageManager defaultManager] cancelImageRequest:requestID];
    }
    
    PHImageRequestOptions *option = [[PHImageRequestOptions alloc] init];
    option.resizeMode = resizeMode;
    option.networkAccessAllowed = YES;
    
    requestID = [[PHCachingImageManager defaultManager] requestImageForAsset:asset targetSize:size contentMode:PHImageContentModeAspectFill options:option resultHandler:^(UIImage * _Nullable image, NSDictionary * _Nullable info) {
        BOOL downloadFinined = ![[info objectForKey:PHImageCancelledKey] boolValue] && ![info objectForKey:PHImageErrorKey];
        if (downloadFinined && completion) {
            completion(image, info);
        }
    }];
}

- (void)requestImageForAsset:(PHAsset *)asset scale:(CGFloat)scale resizeMode:(PHImageRequestOptionsResizeMode)resizeMode completion:(void (^)(UIImage *image))completion
{
    PHImageRequestOptions *option = [[PHImageRequestOptions alloc] init];
    option.resizeMode = resizeMode;//控制照片尺寸
    option.networkAccessAllowed = YES;
    
    [[PHCachingImageManager defaultManager] requestImageDataForAsset:asset options:option resultHandler:^(NSData * _Nullable imageData, NSString * _Nullable dataUTI, UIImageOrientation orientation, NSDictionary * _Nullable info) {
        BOOL downloadFinined = ![[info objectForKey:PHImageCancelledKey] boolValue] && ![info objectForKey:PHImageErrorKey] && ![[info objectForKey:PHImageResultIsDegradedKey] boolValue];
        if (downloadFinined && completion) {
            CGFloat sca = imageData.length/(CGFloat)UIImageJPEGRepresentation([UIImage imageWithData:imageData], 1).length;
            NSData *data = UIImageJPEGRepresentation([UIImage imageWithData:imageData], scale==1?sca:sca/2);
            completion([UIImage imageWithData:data]);
        }
    }];
}

- (BOOL)judgeAssetisInLocalAblum:(PHAsset *)asset
{
    PHImageRequestOptions *option = [[PHImageRequestOptions alloc] init];
    option.networkAccessAllowed = NO;
    option.synchronous = YES;
    
    __block BOOL isInLocalAblum = YES;
    
    [[PHCachingImageManager defaultManager] requestImageDataForAsset:asset options:option resultHandler:^(NSData * _Nullable imageData, NSString * _Nullable dataUTI, UIImageOrientation orientation, NSDictionary * _Nullable info) {
        isInLocalAblum = imageData ? YES : NO;
    }];
    return isInLocalAblum;
}



@end

3.显示相册FWPhotoAlbumTableViewController

#import <UIKit/UIKit.h>
#import <Photos/Photos.h>

@interface FWPhotoAlbumTableViewController : UITableViewController
//最大选择数
@property (nonatomic, assign) NSInteger maxSelectCount;
//是否选择了原图
@property (nonatomic, assign) BOOL isCanSelectMorePhotos;
//当前已经选择的图片
//@property (nonatomic, strong) NSMutableArray<ZLSelectPhotoModel *> *arraySelectPhotos;

//选则完成后回调
//@property (nonatomic, copy) void (^DoneBlock)(NSArray<ZLSelectPhotoModel *> *selPhotoModels, BOOL isSelectOriginalPhoto);
//取消选择后回调
@property (nonatomic, copy) void (^CancelBlock)();


@end

#import "FWPhotoAlbumTableViewController.h"
#import "FWPhotoManager.h"
#import "UIButton+TextAndImageHorizontalDisplay.h"
#import "FWPhotoCollectionViewController.h"
#import "FWPhotosLayout.h"

@interface FWPhotoAlbumTableViewController ()
{
    NSMutableArray<FWPhotoAlbums *> *mArr;
}

@end

@implementation FWPhotoAlbumTableViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor whiteColor];
    self.title = @"相册";
    
    mArr= [[[FWPhotoManager sharedManager] getPhotoAlbums] mutableCopy];
    
    [self initNavgationBar];
    
    self.tableView.separatorStyle = UITableViewCellSeparatorStyleNone;
}

- (void)initNavgationBar
{
    UIButton *rightBar = [UIButton buttonWithType:UIButtonTypeSystem];
    rightBar.frame = CGRectMake(0, 0, 68, 32);
    [rightBar setImage:[UIImage imageNamed:@"Camera"] withTitle:@"相机" forState:UIControlStateNormal];
    [rightBar addTarget:self action:@selector(cameraClicked) forControlEvents:UIControlEventTouchUpInside];
    self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:rightBar];
}

- (void)cameraClicked
{
    
}

#pragma mark - Table view data source

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    return [mArr count];
}

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    return 100;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    static NSString *cellID = @"cellID";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellID];
    if (!cell)
    {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:cellID];
    }
    cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
    FWPhotoAlbums *album = mArr[indexPath.row];
    cell.textLabel.text =album.albumName;
    cell.detailTextLabel.text = [NSString stringWithFormat:@"%d张",album.albumImageCount];
    cell.detailTextLabel.textColor = [UIColor grayColor];
    __block UIImage *img = nil;
    [[FWPhotoManager sharedManager] requestImageForAsset:album.firstImageAsset size:CGSizeMake(60 * 3, 60 * 3) resizeMode:PHImageRequestOptionsResizeModeExact completion:^(UIImage *image, NSDictionary *info) {
        img = image;
    }];
    cell.imageView.image = img;
    cell.imageView.contentMode = UIViewContentModeScaleAspectFill;
    cell.imageView.clipsToBounds = YES;
    return cell;
}

- (BOOL)prefersStatusBarHidden
{
    return YES;
}
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    FWPhotoAlbums *model = [mArr objectAtIndex:indexPath.row];
    FWPhotosLayout *layout = [[FWPhotosLayout alloc] init];
    layout.minimumInteritemSpacing = 1.5;
    layout.minimumLineSpacing = 5.0;
    FWPhotoCollectionViewController *vc = [[FWPhotoCollectionViewController alloc] initWithCollectionViewLayout:layout model:model];
    [self.navigationController pushViewController:vc animated:YES];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

4.显示相册集内所有照片FWPhotoCollectionViewController

#import <UIKit/UIKit.h>
#import <Photos/Photos.h>
#import "FWPhotoAlbums.h"

@interface FWPhotoCollectionViewController : UICollectionViewController

@property (nonatomic, strong) FWPhotoAlbums *model;

- (instancetype)initWithCollectionViewLayout:(UICollectionViewLayout *)layout model:(FWPhotoAlbums *)model;

@end

//
//  FWPhotoCollectionViewController.m
//  FWLifeApp
//
//  Created by Forrest Woo on 16/9/23.
//  Copyright © 2016年 ForrstWoo. All rights reserved.
//

#import "FWPhotoCollectionViewController.h"
#import "FWPhotoCell.h"
#import "FWPhotoManager.h"
#import "FWPhotosLayout.h"
#import "FWDisplayBigImageViewController.h"

@interface FWPhotoCollectionViewController () <UICollectionViewDelegateFlowLayout, UICollectionViewDataSource>
{
    NSArray<PHAsset *> *_dataSouce;
}
@property (nonatomic, strong) PHAssetCollection *assetCollection;
@end

@implementation FWPhotoCollectionViewController

static NSString * const reuseIdentifier = @"Cell";

- (instancetype)initWithCollectionViewLayout:(UICollectionViewLayout *)layout model:(FWPhotoAlbums *)model
{
    if (self = [super initWithCollectionViewLayout:layout]) {
        self.model = model;
    }
    
    return self;
}

- (void)viewDidLoad {
    [super viewDidLoad];
    
    // Uncomment the following line to preserve selection between presentations
    // self.clearsSelectionOnViewWillAppear = NO;
//    self.navigationController.navigationBarHidden = YES;
    // Register cell classes
    CGRect frame = self.collectionView.frame;
    frame.origin.y+=44;
    self.collectionView.frame = frame;
    self.view.backgroundColor = [UIColor whiteColor];

    [self initSource];
}

//- (void)setModel:(FWPhotoAlbums *)model
//{
//    self.model = model;
//    
//    [self initSource];
//}

- (BOOL)prefersStatusBarHidden
{
    return YES;
}
- (void)initSource
{
    [self.collectionView registerClass:[FWPhotoCell class] forCellWithReuseIdentifier:reuseIdentifier];
    self.title = self.model.albumName;
    self.automaticallyAdjustsScrollViewInsets = NO;
    // Do any additional setup after loading the view.
    self.assetCollection = self.model.assetCollection;
    _dataSouce = [[FWPhotoManager sharedManager] getAssetsInAssetCollection:self.assetCollection ascending:YES];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

#pragma mark <UICollectionViewDataSource>

- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
    return 1;
}


- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
    return [_dataSouce count];
}

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
    FWPhotosLayout *lay = (FWPhotosLayout *)collectionViewLayout;
    return CGSizeMake([lay cellWidth],[lay cellWidth]);
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    FWPhotoCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:reuseIdentifier forIndexPath:indexPath];
    PHAsset *asset = _dataSouce[indexPath.row];
    __block UIImage *bImage = nil;
    CGSize size = cell.frame.size;
    size.width *= 3;
    size.height *= 3;
    [[FWPhotoManager sharedManager] requestImageForAsset:asset size:size resizeMode:PHImageRequestOptionsResizeModeFast completion:^(UIImage *image, NSDictionary *info) {
        bImage = image;
    }];
    
    [cell setImage:bImage];
    
    return cell;
}

- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
    PHAsset *asset = _dataSouce[indexPath.row];

    [[FWPhotoManager sharedManager] requestImageForAsset:asset size:PHImageManagerMaximumSize resizeMode:PHImageRequestOptionsResizeModeFast completion:^(UIImage *image, NSDictionary *info) {
        FWDisplayBigImageViewController *vc = [[FWDisplayBigImageViewController alloc] initWithImage:image];
        [self.navigationController pushViewController:vc animated:YES];
    }];
   
}
#pragma mark <UICollectionViewDelegate>

@end

5.布局类

#import <UIKit/UIKit.h>

@interface FWPhotosLayout : UICollectionViewFlowLayout

@property (nonatomic, assign,readonly)CGFloat cellWidth;

@end

#import "FWPhotosLayout.h"

@interface FWPhotosLayout ()
@property NSInteger countOfRow;
@end

@implementation FWPhotosLayout

- (void)prepareLayout
{
    [super prepareLayout];
    
    self.countOfRow = ceilf([self.collectionView numberOfItemsInSection:0] / 4.0);
}

- (UICollectionViewLayoutAttributes*)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath
{
    UICollectionViewLayoutAttributes *attris = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:indexPath];
    NSInteger currentRow = indexPath.item / 4;
    
    CGRect frame = CGRectMake( (indexPath.item % 4) * ([self cellWidth] + 5),currentRow * ([self cellWidth] + 65), [self cellWidth], [self cellWidth]);
    attris.frame = frame;
    attris.zIndex = 1;
    
    return attris;
}

- (CGFloat)cellWidth
{
    return (WIDTH - 3 * 5) / 4;
}

- (CGSize)collectionViewContentSize
{
    return CGSizeMake(WIDTH, self.countOfRow * ([self cellWidth] + 5) + 44);
}
@end

代码下载