在沙盒应用中访问桌面

Question

我正在构建一个具有打开新截图的功能的应用程序.我想使用Mac App Store分发它.不幸的是,它需要沙盒.

为了找到新的屏幕截图,我运行了一个NSMetaDataQuery.它会返回一些条目,但遗憾的是我无法获取他们的URL,因为它们位于桌面上(在我的应用程序的沙箱中).

我怎样才能解决这个问题 ？

这是一些代码

query = [[NSMetadataQuery alloc] init];

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(queryUpdated:) name:NSMetadataQueryDidStartGatheringNotification object:query];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(queryUpdated:) name:NSMetadataQueryDidUpdateNotification object:query];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(queryUpdated:) name:NSMetadataQueryDidFinishGatheringNotification object:query];

[query setDelegate:self];
[query setPredicate:[NSPredicate predicateWithFormat:@"kMDItemIsScreenCapture = 1"]];
[query startQuery];

---

numberOfScreenshots = [query resultCount];
[self uploadToAmazonS3:[[[query results]objectAtIndex:([query resultCount]-1)]valueForAttribute:NSMetadataItemURLKey]];

谢谢

Answer 1

在不询问用户权限的情况下,您只能访问音乐,电影,图片和下载文件夹.

您必须要求用户授予您访问桌面文件夹的权限.然后使用名为Security-Scoped Bookmarks的机制,在AppSandboxDesignGuide中阅读更多相关信息.

1. 使用NSOpenPanel选择目录.
2. 保存书签以备将来使用,例如在NSUserDefaults中.
3. 获取访问权限

1和2

    NSOpenPanel *openPanel = [[NSOpenPanel alloc] init];
    [openPanel setCanChooseFiles:NO];
    [openPanel setCanChooseDirectories:YES];
    [openPanel setCanCreateDirectories:YES];

    [openPanel beginWithCompletionHandler:^(NSInteger result){
        if (result == NSFileHandlingPanelOKButton) {
            for (NSURL *fileURL in [openPanel URLs]) {
                NSString *filename = [fileURL path];
                [[NSUserDefaults standardUserDefaults] setObject:filename forKey:@"PathToFolder"];

                NSError *error = nil;
                NSData *bookmark = [fileURL bookmarkDataWithOptions:NSURLBookmarkCreationWithSecurityScope
                     includingResourceValuesForKeys:nil
                                      relativeToURL:nil
                                              error:&error];
                if (error) {
                    NSLog(@"Error creating bookmark for URL (%@): %@", fileURL, error);
                    [NSApp presentError:error];
                } else {
                    [[NSUserDefaults standardUserDefaults] setObject:bookmark forKey:@"PathToFolder"];
                    [[NSUserDefaults standardUserDefaults] synchronize];
                }
                break;
            }
        }        
}];

3.

    NSError *error = nil;
    NSData *bookmark = [[NSUserDefaults standardUserDefaults] objectForKey:@"PathToFolder"];
    bookmarkedURL = [NSURL URLByResolvingBookmarkData:bookmark options:NSURLBookmarkResolutionWithSecurityScope relativeToURL:nil bookmarkDataIsStale:nil error:&error];
    BOOL ok = [bookmarkedURL startAccessingSecurityScopedResource];
    NSLog(@"Accessed ok: %d %@", ok, [bookmarkedURL relativePath]);

所以,那就是它.

Answer 2

允许访问后，您还需要获取真实主文件夹的路径 - 所有其他文件 API 仅提供沙盒文件夹的路径，即使已启用对真实文件夹的访问也是如此。为了解决这个烦人的问题，Apple 建议这样做以获取真正的主文件夹：

#include <sys/types.h>
#include <pwd.h>

const char *home = getpwuid(getuid())->pw_dir;
NSString *path = [[NSFileManager defaultManager] 
                  stringWithFileSystemRepresentation:home
                  length:strlen(home)];
NSString *realHomeDirectory = [[NSURL fileURLWithPath:path isDirectory:YES] path];