获取 ALAsset 的路径

Question

如何获取 ALAsset 数组中每个项目的路径？

我想获取图像，以便将它们添加到电子邮件中，

例如

NSString *path = [[NSBundle mainBundle] pathForResource:@"sample" ofType:@"png"];
NSData *myData = [NSData dataWithContentsOfFile:path];
[mailViewController addAttachmentData:myData mimeType:@"image/png" fileName:@"sample"];

这怎么能做到呢？

Answer 1

假设您已经有权访问 ALAsset 对象数组，您可以像这样检索它们的 URL：

someAsset.defaultRepresentation.url

Answer 2

假设您有资产 URL，例如 asset-library://asset/asset.JPG?id=1000000477&ext=JPG：

      ALAssetsLibraryAssetForURLResultBlock resultblock = ^(ALAsset *myasset)
      {
             // [[myasset defaultRepresentation] fullResolutionImage]
             // is a CGImageRef so you can process it like you would any CGImageRef to save to disk, resize, etc. 

                NSURL *urlPath = [[NSURL fileURLWithPath:[[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject]] URLByAppendingPathComponent:@"somefile.png"];

                CGImageDestinationRef ref = CGImageDestinationCreateWithURL((CFURLRef)urlPath, kUTTypePNG, 1, NULL);
                CGImageDestinationAddImage(ref, (CGImageRef)[[myasset defaultRepresentation] fullResolutionImage], NULL);

                NSDictionary *props = [[NSDictionary dictionaryWithObjectsAndKeys:
                                        [NSNumber numberWithFloat:1.0], kCGImageDestinationLossyCompressionQuality,
                                        nil] retain];

                CGImageDestinationSetProperties(ref, (CFDictionaryRef) props);

                CGImageDestinationFinalize(ref);
                CFRelease(ref);

        };

        NSURL *asseturl = [NSURL URLWithString:mediaurl];
        ALAssetsLibrary* assetslibrary = [[[ALAssetsLibrary alloc] init] autorelease];

        NSString *asseturl = @"assets-library://asset/asset.JPG?id=1000000477&ext=JPG";

        [assetslibrary assetForURL:asseturl 
                       resultBlock:resultblock
                      failureBlock:^(NSError *error) {
                          NSLog(@"error couldn't get photo");
                      }]; 

Answer 3

如果您有 ALAsset 数组，则可以加载资产数据。

for (ALAsset *asset in assetsArray)
{
    // You cannot use ALAsset URL for file access in NSFileManager or NSData.
    // Get asset data. But be careful with very large data:
    ALAssetRepresentation *rep = [asset defaultRepresentation];
    unsigned long repSize      = (unsigned long)rep.size;

    Byte *buffer      = (Byte *)malloc(repSize);
    NSUInteger length = [rep getBytes:buffer fromOffset:0 length:repSize error:nil];

    NSData *myData = [NSData dataWithBytesNoCopy:buffer length:length freeWhenDone:YES];


    // fileName parameter in addAttachmentData:mimeType:fileName: can be any string.
    // You can take asset file name:
    NSString *fileName = [rep filename];

    // Then use in call:
    [mailViewController addAttachmentData:myData mimeType:@"image/png" fileName:fileName];
}