UIImageWriteToSavedPhotosAlbum 仅保存 10 张图像中的 5 张。为什么？

Question

正如标题所示，我遇到了问题。 是否有任何限制，例如“每秒仅导出 3 个图像”或类似的限制？

        for (int frameStepper = 0; frameStepper < [Something frameCount]; frameStepper++)
        {
            //Get the filename.
            imagePath = [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"frame_%i.jpg", frameStepper]];

            //Read image.
            UIImage *image = [[[UIImage alloc] initWithContentsOfFile:imagePath] autorelease];

            //Write image.
            UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil);
        }

执行此代码后，我导出了 10 张图像中的 5 张。看不出为什么。请帮忙，非常感谢。

Answer 1

这个的一个变体帮助了我：
http://iphoneincubator.com/blog/tag/uiimagewritetosavedphotosalbum

{
    UIImageWriteToSavedPhotosAlbum(image, self, @selector(imageSavedToPhotosAlbum: didFinishSavingWithError: contextInfo:), nil);

}


- (void)imageSavedToPhotosAlbum:(UIImage *)image didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo {
    if (error) {
        [self tryWriteAgain:image];
    }
}

-(void)tryWriteAgain:(UIImage *)image
{
    UIImageWriteToSavedPhotosAlbum(image, self, @selector(imageSavedToPhotosAlbum: didFinishSavingWithError: contextInfo:), nil);
}

Answer 2

如果我记录完成错误，它会说：

Error Domain=ALAssetsLibraryErrorDomain Code=-3301 "Write busy" UserInfo=0x69e8e20 {NSLocalizedFailureReason=There was a problem writing this asset because the writing resources are busy., NSLocalizedRecoverySuggestion=Try to write again, NSLocalizedDescription=Write busy}

这意味着我必须通过实现给定的回调来等待正在运行的进程完成：

- (void)               image: (UIImage *) image
    didFinishSavingWithError: (NSError *) error
                 contextInfo: (void *) contextInfo

Hurray。