无法弄清楚 IOS 4.2 中的此文件行为

Question

文件行为的奇怪行为。事情是这样的：我正在使用手机摄像头拍摄照片，并在内部生成缩略图。我将它们保存为文档目录中的临时文件。

这是完整的代码：

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info {

UIImage *photo = [info objectForKey:@"UIImagePickerControllerOriginalImage"];
photo = [self scaleAndRotateImage:photo];

// save photo
NSString *docsDir = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents"];
NSLog(@"Writing to %@",docsDir);

// save photo file
NSLog(@"Saving photo as %@",[NSString stringWithFormat:@"%@/temp_photo.png",docsDir]);
[UIImagePNGRepresentation(photo) writeToFile:[NSString stringWithFormat:@"%@/temp_photo.png",docsDir] atomically:YES];

// make and save thumbnail
NSLog(@"Saving thumbnail as %@",[NSString stringWithFormat:@"%@/temp_thumb.png",docsDir]);
UIImage *thumb = [self makeThumbnail:photo];
[UIImagePNGRepresentation(thumb) writeToFile:[NSString stringWithFormat:@"%@/temp_thumb.png",docsDir] atomically:YES];

NSFileManager *manager = [NSFileManager defaultManager];    
NSError *error;
NSArray *files = [manager contentsOfDirectoryAtPath:docsDir error:&error];
NSLog(@"\n\nThere are %d files in the documents directory %@",(files.count),docsDir);

for (int i = 0; i < files.count; i++) {
    NSString *filename = [files objectAtIndex:i];
    NSLog(@"Seeing filename %@",filename);
}

// done
//[photo release];
//[thumb release];
[self dismissModalViewControllerAnimated:NO];
[delegate textInputFinished];
}

如您所见，我在这里进行了大量的登录操作，试图找出我的问题（即将出现）。此时的日志输出是：

Writing to /var/mobile/Applications/77D792DC-A224-4A47-8A4C-BB7C557626F3/Documents

Saving photo as /var/mobile/Applications/77D792DC-A224-4A47-8A4C-BB7C557626F3/Documents/temp_photo.png

Saving thumbnail as /var/mobile/Applications/77D792DC-A224-4A47-8A4C-BB7C557626F3/Documents/temp_thumb.png

There are 3 files in the documents directory /var/mobile/Applications/77D792DC-A224-4A47-8A4C-BB7C557626F3/Documents

Seeing filename temp_photo.png

Seeing filename temp_text.txt

Seeing filename temp_thumb.png

这绝对符合预期。我的设备上显然有三个文件。这是下一个运行的代码 - 接收 textInputFinished 消息的代码：

- (void)textInputFinished {

NSFileManager *fileManager = [NSFileManager defaultManager];
NSString *docsDir = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents"];
NSError *error;

// get next filename
NSString *filename;
int i = 0;
do {
    i++;
    filename = [NSString stringWithFormat:@"%@/reminder_%d",docsDir,i];
    NSLog(@"Trying filename %@",filename);
} while ([fileManager fileExistsAtPath:[filename stringByAppendingString:@".txt"]]);

NSLog(@"New base filename is %@",filename);

NSArray *files = [fileManager contentsOfDirectoryAtPath:docsDir error:&error];
NSLog(@"There are %d files in the directory %@",(files.count),docsDir);

这是测试获取新的、非临时的、未使用的文件名。它确实做到了 - 但随后它说文档文件夹中没有任何文件！这是记录的输出：

Trying filename /var/mobile/Applications/77D792DC-A224-4A47-8A4C-BB7C557626F3/Documents/reminder_1

New base filename is /var/mobile/Applications/77D792DC-A224-4A47-8A4C-BB7C557626F3/Documents/reminder_1

There are 0 files in the directory /var/mobile/Applications/77D792DC-A224-4A47-8A4C-BB7C557626F3/Documents

到底是什么？这三个文件去哪了？

Answer 1

我想知道像这样获取文档目录是否会有所不同：

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];

Answer 2

这看起来像是一个奇怪的答案，但由于我最近在 UIImagePickerController 上遇到了一些特殊的图像可用性问题，请尝试以下操作：在选择器的委托调用之后立即关闭并释放它：

- (void)imagePickerController:(UIImagePickerController *)picker 
                      didFinishPickingMediaWithInfo:(NSDictionary *)info {
    [picker dismissModalViewControllerAnimated:NO];
    [picker release];

然后继续处理其余的代码。由于我不知道的原因，info 的内容直到发布后才真正可用。

如果这最终是您的解决方案，我仍然不明白为什么这些文件似乎存在然后消失。尽管如此，还是值得一试。