如何在iPhone庫中獲取最新照片？

Question

在我的應用程序中有一個按鈕，用戶只需單擊它，然后可以直接在屏幕上檢索庫中的最新照片。 如何在圖書館中獲取最新照片？

---

2012/02/17

這可以獲得ALAsset

void (^assetEnumerator)(ALAsset *, NSUInteger, BOOL *) = ^(ALAsset *result, NSUInteger index, BOOL *stop)
    {
        if(result != nil)
        {

            [self.assets addObject:result];

        }
    };

    void (^assetGroupEnumerator)(ALAssetsGroup *, BOOL *) = ^(ALAssetsGroup *group, BOOL *stop)
    {
        if(group != nil)
        {
            [group setAssetsFilter:[ALAssetsFilter allPhotos]];
            [group enumerateAssetsUsingBlock:assetEnumerator];
        }else{
            self.image = [self getLastImage];

        }

    };
    ALAssetsLibraryAccessFailureBlock failureblock = ^(NSError *myerror){
        NSLog(@"error occour =%@", [myerror localizedDescription]);
    };


    assets = [[NSMutableArray alloc] init];
    ALAssetsLibrary *assetsLibrary = [[ALAssetsLibrary alloc] init];
    [assetsLibrary enumerateGroupsWithTypes:ALAssetsGroupAll usingBlock:assetGroupEnumerator failureBlock:failureblock];
    [assetsLibrary release];

要獲取文件日期，我使用它

    assetURLArray = [[NSMutableArray alloc] init];
    for (ALAsset *asset in self.assets) {
        NSDate * date = [asset valueForProperty:ALAssetPropertyDate];

然后我發現最新的圖像總是屬於assetURLArray的頂級圖像，所以我終於得到了這樣的最新圖像

if (self.assets && [self.assets count]) {
        ALAsset *asset = [self.assets objectAtIndex:([self.assets count] - 1)];
        CGImageRef ref = [[asset defaultRepresentation]fullResolutionImage];

我不知道如果這總是有效的......希望任何人都可以證明我。

在那里，我正在尋找一種同步線程的方法......

Answer 1

您可以通過遵循ALAssetsGroup的方法來完成

(void)enumerateAssetsWithOptions:(NSEnumerationOptions)options usingBlock:(ALAssetsGroupEnumerationResultsBlock)enumerationBlock;**

    applying **NSEnumerationReverse** option

    void (^assetEnumerator)(ALAsset *, NSUInteger, BOOL *) = ^(ALAsset *result, NSUInteger index, BOOL *stop)
        {
            if(result != nil)
            {

                [self.assets addObject:result];

            }
        };

        void (^assetGroupEnumerator)(ALAssetsGroup *, BOOL *) = ^(ALAssetsGroup *group, BOOL *stop)
        {
            if(group != nil)
            {
                [group setAssetsFilter:[ALAssetsFilter allPhotos]];
                [group enumerateAssetsWithOptions:NSEnumerationReverse usingBlock:assetEnumerator];
            }

        };
        ALAssetsLibraryAccessFailureBlock failureblock = ^(NSError *myerror){
            NSLog(@"error occour =%@", [myerror localizedDescription]);
        };


        assets = [[NSMutableArray alloc] init];
        ALAssetsLibrary *assetsLibrary = [[ALAssetsLibrary alloc] init];
        [assetsLibrary enumerateGroupsWithTypes:ALAssetsGroupSavedPhotos usingBlock:assetGroupEnumerator failureBlock:failureblock];
        [assetsLibrary release];


    **Your self.assets array will have latest images**

Answer 2

此代碼段可以檢索ALAsset ：

void (^assetEnumerator)(ALAsset *, NSUInteger, BOOL *) = ^(ALAsset *result, NSUInteger   
index, BOOL *stop) {
    if(result != nil) {
        [self.assets addObject:result];
    }
};

void (^assetGroupEnumerator)(ALAssetsGroup *, BOOL *) = ^(ALAssetsGroup *group, BOOL *stop) {
    if(group != nil) {
        [group setAssetsFilter:[ALAssetsFilter allPhotos]];
        [group enumerateAssetsUsingBlock:assetEnumerator];
    } else {
        self.image = [self getLastImage];
    }
};

ALAssetsLibraryAccessFailureBlock failureblock = ^(NSError *myerror) {
    NSLog(@"error occour =%@", [myerror localizedDescription]);
};

assets = [[NSMutableArray alloc] init];
ALAssetsLibrary *assetsLibrary = [[ALAssetsLibrary alloc] init];
[assetsLibrary enumerateGroupsWithTypes:ALAssetsGroupAll usingBlock:assetGroupEnumerator failureBlock:failureblock];
[assetsLibrary release];

要獲取文件日期，我使用：

assetURLArray = [[NSMutableArray alloc] init];
for (ALAsset *asset in self.assets) {
    NSDate * date = [asset valueForProperty:ALAssetPropertyDate];

然后我發現最新的圖像總是屬於assetURLArray的頂級圖像，所以我終於得到了這樣的最新圖像：

if (self.assets && [self.assets count]) {
    ALAsset *asset = [self.assets objectAtIndex:([self.assets count] - 1)];
    CGImageRef ref = [[asset defaultRepresentation] fullResolutionImage];

我不知道這是否總能奏效......我希望有人能夠澄清我的疑慮。

在那里，我正在尋找一種同步線程的方法......

---

2012-04-03更新

現在我使用NSNotification來解決這個問題：

- (void)gotLastImageCallBack {
    if (notifyName) {
        [[NSNotificationCenter defaultCenter] postNotificationName:notifyName object:nil];
    }
}

獲取圖像后，通知會將回調發送回相關類。

Answer 3

您需要將所有照片創建日期，然后按日期對其進行排序。

- (NSDictionary *) attributesForFile:(NSURL *)anURI {

// note: singleton is not thread-safe
NSFileManager *fileManager = [NSFileManager defaultManager];
NSString *aPath = [anURI path];

if (![fileManager fileExistsAtPath:aPath]) return nil;

NSError *attributesRetrievalError = nil;
NSDictionary *attributes = [fileManager attributesOfItemAtPath:aPath
                           error:&attributesRetrievalError];

if (!attributes) {
   NSLog(@"Error for file at %@: %@", aPath, attributesRetrievalError);
   return nil;
}

NSMutableDictionary *returnedDictionary = 
   [NSMutableDictionary dictionaryWithObjectsAndKeys:
        [attributes fileType], @"fileType",
        [attributes fileModificationDate], @"fileModificationDate",
        [attributes fileCreationDate], @"fileCreationDate",
        [NSNumber numberWithUnsignedLongLong:[attributes fileSize]], @"fileSize",
    nil];

return returnedDictionary;
}

Answer 4

UIButton *photoAlbum = [[UIButton alloc] init];
[photoAlbum addTarget:self action:@selector(getLatestPhoto:) forControlEvents:UIControlEventTouchDown];

 -(void)getLatestPhoto
{
    ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];

    [library enumerateGroupsWithTypes:ALAssetsGroupLibrary usingBlock:^(ALAssetsGroup *group, BOOL *stop)
    {
        [group setAssetsFilter:[ALAssetsFilter allPhotos]];
        if ([group numberOfAssets] > 0)
        {
            [group enumerateAssetsAtIndexes:[NSIndexSet indexSetWithIndex:[group numberOfAssets]-1] options:0
                             usingBlock:^(ALAsset *alAsset, NSUInteger index, BOOL *innerStop)
             {

             }];
        }
    }
        failureBlock: ^(NSError *error)
    {
        NSLog(@"No Photo");
    }];
}

Answer 5

做這個家伙吧

void (^enumerate)(ALAssetsGroup *, BOOL *) = ^(ALAssetsGroup *group, BOOL *stop)
{
    if ([[group valueForProperty:@"ALAssetsGroupPropertyType"] intValue] == ALAssetsGroupSavedPhotos)
    {
        NSLog(@"Camera roll");
        [group enumerateAssetsUsingBlock:^(ALAsset *result, NSUInteger index, BOOL *stop) {
            if(result != nil){
                ALAssetRepresentation *rep = [result defaultRepresentation];
                [thumbnailsArray insertObject:rep atIndex:0];
            }

        }];
    }