检索ALAsset的文件名 [英] Retrieving a filename for an ALAsset
问题描述
如何从ALAsset中提取文件名?
How can the filename be extracted from an ALAsset?
有没有办法通过网址或其他方式获取此文件?
Is there a way to get this via the url or some other way?
推荐答案
更新:正如下面的yeonsh所述,从iOS 5.0开始,有一种更好的方法。这个答案与iOS< 5.0。
Update: As yeonsh notes below, from iOS 5.0 there is a better way. This answer is relevant for iOS < 5.0.
您可以从ALAsset中提取URL,但所有文件名都相同,格式为
You can extract an URL from the ALAsset, but all the filenames are the same, on the form
assets-library://asset/asset.JPG?id = 1000000001& ext = JPG
assets-library://asset/asset.JPG?id=1000000001&ext=JPG
如果由于某种原因需要不同的文件名,请尝试制作内部文件 - 外部范例:
If you for some reason need different file names, try making an internal-external paradigm:
#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
请注意,您不需要用于读取ALAsset内容的文件名。使用ALAsset.defaultRepresentation.getBytes方法。
Note that you do not need a filename to read the content of an ALAsset. Use the ALAsset.defaultRepresentation.getBytes method for that.
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