使用QLPreviewController显示ALAsset

Question

我想使用QLPreviewController来显示来自照片流的ALAssets QLPreviewController需要一个NSURL来显示项目

如果是文件URL (如/var/mobile/Applications/5374......9E0/Documents/image33.png )，则效果很好

我有一个ALAsset，但是使用[asset defaultRepresentation url]可以得到一个NSURL类型。

assets-library://asset/asset.JPG?id=00000000-0000-0000-0000-000000000075&ext=JPG

但这并不显示QLPreviewController只是一直显示正在加载?？

有什么想法吗？提前感谢

Answer 1

也许不是最快最有效的方法，但它解决了问题。请按照文档中的说明使用NSFilemanager而不是NSTemporaryDirectory :-)确保链接到ImageIO.framework

    #import <ImageIO/ImageIO.h>

    ....
    NSURL *outURLToUseWithQLPreviewController = nil;

    ALAsset *myAsset = ... // received somehow
    ALAssetRepresentation *represent = myAsset.defaultRepresentation;
    CGImageRef representFullScreen = represent.fullScreenImage;

    NSString *tempDir = NSTemporaryDirectory();
    NSString *imagePath = [tempDir stringByAppendingPathComponent:represent.filename];
    NSURL *tempURL = [NSURL fileURLWithPath:imagePath];

    CGImageDestinationRef destination = CGImageDestinationCreateWithURL((__bridge CFURLRef)(tempURL), (__bridge CFStringRef)(represent.UTI), 1, NULL);
    CGImageDestinationAddImage(destination, representFullScreen, nil);
    if ( CGImageDestinationFinalize(destination) ) {
        outURLToUseWithQLPreviewController = tempURL;
    }
    return outURLToUseWithQLPreviewController;