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ALAssetsgroup
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Enumerating Assets(遍歷資源)
– enumerateAssetsUsingBlock:(用一個block來遍歷組裏的資源)
– enumerateAssetsWithOptions:usingBlock:(在枚舉選項的條件下,用一個block來遍歷組裏的資源)
– enumerateAssetsAtIndexes:options:usingBlock:(在枚舉選項的條件下,用一個block來遍歷組裏特定index的資源)
-
Adding Assets(添加資源)
-
– addAsset:(添加一個已存在的asset到接收者。返回yes成功;反之,失敗。)
editable
property(指示程序是否可以編輯組,只讀屬性,打印看了一下,系統自帶的是不能編輯的,其它可以編輯)-
Filtering(過濾)
– numberOfAssets(返回組過濾器條件下的資源個數,若沒有設置過濾器,則返回組裏的資源個數)
– setAssetsFilter:(設置組的過濾器)
-
Accessing Properties(訪問屬性)
– valueForProperty:(通過組屬性名稱,獲取組屬性:組名稱,組類型,組永久性ID,組URL)
– posterImage(組的封面)
ALAsset
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Asset Properties
– valueForProperty:
(1.ALAssetPropertyType 資源的類型(照片,視頻)
2.ALAssetPropertyLocation 資源地理位置(無位置信息返回null)
3.ALAssetPropertyDuation 播放時長(照片返回ALErorInvalidProperty)
- 4.ALAssetPropertyOrientation 方向(共有8個方向,參見:ALAssetOrientation)
- 5.ALAssetPropertyDate 拍攝時間(包含了年與日時分秒)
- 6.ALAssetPropertyRepresentations 描述(打印看了下,只有帶後綴的名稱)
- 7.ALAssetPropertyURLs(返回一個字典,鍵值分別是文件名和文件的url)
- 8.ALAssetPropertyAssetURL 文件的url )
editable
property(指示資源是否可以編輯,只讀屬性)originalAsset
property(原始資源。若沒有保存修改後資源,則原始資源爲nil)
Accessing Representations
– defaultRepresentation
– representationForUTI:
– thumbnail(小正方形的縮略圖)
– aspectRatioThumbnail(按原始資源長寬比例的縮略圖)
Setting New Image and Video Data
– setImageData:metadata:completionBlock:
用給定的image data 替換接收者的image data。
- – setVideoAtPath:completionBlock:
- 用給定的URL的video
替換接收者的video data。
Saving to the Saved Photos Album
– writeModifiedImageDataToSavedPhotosAlbum:metadata:completionBlock:
保存image data到Saved Photos album
– writeModifiedVideoAtPathToSavedPhotosAlbum:completionBlock:
保存video到Saved Photos album的指定路徑
ALAssetRepresentation
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ALAssetRepresentation對象封裝了一個給定ALAsset對象的陳述。
Getting Image Representations
– CGImageWithOptions:
– fullResolutionImage(完全分辨率的圖片)
– fullScreenImage(滿屏的圖片)
Getting Image Attributes
– orientation(文件方向)
– scale(長寬比例)
– filename(文件名字)
Getting Raw Data
– size(文件尺寸,以byte爲單位)
– getBytes:fromOffset:length:error:
Getting Metadata
Getting an URL
使用
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- -(void)getGroup
- {
- @autoreleasepool
- {
- ALAssetsLibraryAccessFailureBlock failureblock =
- ^(NSError *myerror)
- {
- NSLog(@"相冊訪問失敗 =%@", [myerror localizedDescription]);
- if ([myerror.localizedDescription rangeOfString:@"Global denied access"].location!=NSNotFound) {
- NSLog(@"無法訪問相冊.請在'設置->定位服務'設置爲打開狀態.");
- }else{
- NSLog(@"相冊訪問失敗.");
- }
- };
- ALAssetsLibraryGroupsEnumerationResultsBlock
- libraryGroupsEnumeration = ^(ALAssetsGroup* group,BOOL* stop)
- {
- if (group!=nil)
- {
- [self.groupArray addObject:group];
- }
- else
- {
- if (!_groupTable)
- {
- _groupTable = [[UITableView alloc] initWithFrame:EZRECT(0, 0, SCREEN_SIZE_WIDTH, SCREEN_SIZE_HEIGHT - 44)
- style:UITableViewStylePlain];
- _groupTable.delegate = self;
- _groupTable.dataSource = self;
- [self.view addSubview:_groupTable];
- }
- [_groupTable performSelectorOnMainThread:@selector(reloadData) withObject:nil waitUntilDone:NO];
- }
- };
- [[DataCenter defaultAssetsLibrary] enumerateGroupsWithTypes:ALAssetsGroupAll
- usingBlock:libraryGroupsEnumeration
- failureBlock:failureblock];
- }
- }
由於分組在添加到groupArray中,後面要在外面的函數中調用,這樣會發生警告,所以,將ALAssetsLibrary的獲取寫成一個單例
- + (ALAssetsLibrary *)defaultAssetsLibrary
- {
- static dispatch_once_t pred = 0;
- static ALAssetsLibrary *library = nil;
- dispatch_once(&pred,
- ^{
- library = [[ALAssetsLibrary alloc] init];
- });
- return library;
- }
利用獲得的分組再來獲取資源文件:
- -(void)filterImageWithGroup:(ALAssetsGroup *)group
- {
- [self.images removeAllObjects];
- ALAssetsGroupEnumerationResultsBlock groupEnumerAtion =
- ^(ALAsset *result,NSUInteger index, BOOL *stop)
- {
- if (result!=NULL)
- {
- if ([[result valueForProperty:ALAssetPropertyType]isEqualToString:ALAssetTypePhoto])
- {
- [self.images addObject:result];
- }
- }
- else
- {
- //主線程中刷新UI
- }
- };
- [group enumerateAssetsUsingBlock:groupEnumerAtion];
- }