檢索ALAsset的文件名

Question

如何從ALAsset中提取文件名？

有沒有辦法通過URL或其他方式來得到這個？

Answer 1

更新：正如yeonsh注意到的，從iOS 5.0開始有更好的方法。此答案與iOS < 5.0相關。

您可以從中提取ALAsset的URL，但所有的文件名是相同的，在表格上

資產庫：//asset/asset.JPG ID = 1000000001 & EXT = JPG

如果你因爲某些原因需要不同的文件名，請嘗試的內外範例：

#import <Foundation/Foundation.h> 

@interface NSURL (NSURL_Asset) 

- (NSURL*) toExternalForm; 
- (NSURL*) fromExternalForm; 
- (NSString*) toExternalFilename;  

@end 

#import "NSURL+Asset.h" 
#import "URLParser.h" // from http://iphone.demay-fr.net/2010/04/parsing-url-parameters-in-a-nsstring/ 

static NSString *const EXTERNAL_TOKEN = @"/assetExternalForm/"; 

@implementation NSURL (NSURL_Asset) 

// assets-library://asset/asset.JPG/assetExternalForm/1000000001.JPG -> assets-library://asset/asset.JPG?id=1000000001&ext=JPG 
- (NSURL*) fromExternalForm { 
    if([self.scheme isEqualToString:@"assets-library"]) { 
     NSRange slash = [self.absoluteString rangeOfString:EXTERNAL_TOKEN options:NSBackwardsSearch]; 
     if(slash.location != NSNotFound) { 

      NSRange dot = [self.absoluteString rangeOfString:@"." options:NSBackwardsSearch]; 

      if(dot.location != NSNotFound) { 
       NSString* extention = [self.absoluteString substringFromIndex:(dot.location + dot.length)]; 
       NSString* identifier = [self.absoluteString substringWithRange:NSMakeRange(slash.location + slash.length, dot.location - (slash.location + slash.length))]; 

       return [NSURL URLWithString:[NSString stringWithFormat:@"%@?id=%@&ext=%@", [self.absoluteString substringToIndex:slash.location], identifier, extention]]; 
      } 
     } 
    } 
    return self; 
} 

// assets-library://asset/asset.JPG?id=1000000001&ext=JPG -> assets-library://asset/asset.JPG/assetExternalForm/1000000001.JPG 
- (NSURL*) toExternalForm { 
    if([self.scheme isEqualToString:@"assets-library"]) { 
     NSRange range = [self.absoluteString rangeOfString:@"?"]; 
     if(range.location != NSNotFound) { 
      URLParser *parser = [[[URLParser alloc] initWithURLString:self.absoluteString] autorelease]; 

      NSString* extention = [parser valueForVariable:@"ext"]; 
      NSString* identifier = [parser valueForVariable:@"id"]; 

      if(extention != NULL && identifier != NULL) { 
       return [NSURL URLWithString:[NSString stringWithFormat:@"%@%@%@.%@", [self.absoluteString substringToIndex:range.location], EXTERNAL_TOKEN, identifier, extention]]; 
      } 
     } 
    } 
    return self; 
} 

// assets-library://asset/asset.JPG?id=1000000001&ext=JPG -> 1000000001.JPG 
- (NSString*) toExternalFilename { 
    if([self.scheme isEqualToString:@"assets-library"]) { 
     NSRange range = [self.absoluteString rangeOfString:@"?"]; 
     if(range.location != NSNotFound) { 
      URLParser *parser = [[[URLParser alloc] initWithURLString:self.absoluteString] autorelease]; 

      NSString* extention = [parser valueForVariable:@"ext"]; 
      NSString* identifier = [parser valueForVariable:@"id"]; 

      if(extention != NULL && identifier != NULL) { 
       return [NSString stringWithFormat:@"%@.%@", identifier, extention]; 
      } 
     } 
    } 
    return NULL; 
} 

@end 

注意，你並不需要一個文件名來讀取ALAsset的內容。使用ALAsset.defaultRepresentation.getBytes方法。

Answer 2

從iOS的5.0你可以從ALAssetRepresentation類文件。

ALAssetRepresentation *rep = [anAssetItem defaultRepresentation]; 
NSString *fileName = [rep filename];