iOS:无法将文件保存到"应用程序支持"文件夹,但可以"文档"

Question

我可以将二进制文件下载并保存到'Documents'文件夹中,并且自定义名称完全正常.

如果我只是将URL更改为"应用程序支持"文件夹而不是"文档"文件夹,则无法写入该URL,表明它不存在.

这是URL构造代码:

- ( NSURL * ) getSaveFolder
{
    NSURL * appSupportDir    = nil;
    NSURL * appDirectory     = nil;
    NSArray * possibleURLs   = [[NSFileManager defaultManager] URLsForDirectory:NSApplicationSupportDirectory inDomains:NSAllDomainsMask];

    if ( [possibleURLs count] >= 1 )
    {
        appSupportDir = [possibleURLs objectAtIndex:0];
    }

    if ( appSupportDir != nil)
    {
        NSString * appBundleID = [[NSBundle mainBundle] bundleIdentifier];
        appDirectory           = [appSupportDir URLByAppendingPathComponent:appBundleID];
    }

    return appSupportDir;
}

这是保存代码:

- ( void ) writeOutDataToFile:( NSData * )data
{

    NSURL * finalURL = [self.rootPathURL URLByAppendingPathComponent:self.aFileName];

    [data writeToURL:finalURL atomically:YES];
}

---

如果我将NSArray更改为:

NSArray * possibleURLs   = [[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask];

然后它保存好.

我已经阅读了Apple Docs on File的东西,无法解决这个问题 - 我错过了什么？

Answer 1

与Documents目录不同Application Support,默认情况下,该应用程序的沙箱中不存在该目录.您需要先创建它才能使用它.

获取目录引用的一种更简单的方法是:

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSApplicationSupportDirectory, NSUserDomainMask, YES);
NSString *appSupportDirectory = paths.firstObject;

Answer 2

如果有人不确定如何做rmaddy所描述的:

NSString *appSupportDir = [NSSearchPathForDirectoriesInDomains(NSApplicationSupportDirectory, NSUserDomainMask, YES) lastObject];
//If there isn't an App Support Directory yet ... 
if (![[NSFileManager defaultManager] fileExistsAtPath:appSupportDir isDirectory:NULL]) {
    NSError *error = nil;
//Create one 
    if (![[NSFileManager defaultManager] createDirectoryAtPath:appSupportDir withIntermediateDirectories:YES attributes:nil error:&error]) {
        NSLog(@"%@", error.localizedDescription);
    }
    else {
// *** OPTIONAL *** Mark the directory as excluded from iCloud backups 
        NSURL *url = [NSURL fileURLWithPath:appSupportDir];
        if (![url setResourceValue:@YES
                            forKey:NSURLIsExcludedFromBackupKey
                             error:&error])
        {
            NSLog(@"Error excluding %@ from backup %@", url.lastPathComponent, error.localizedDescription);
        }
        else {
            NSLog(@"Yay");
        }
    }
}

Answer 3

我遇到了同样的问题,并决定使用更简洁的方法:

let fileManager = NSFileManager.defaultManager()
let urls = fileManager.URLsForDirectory(.ApplicationSupportDirectory, inDomains: .UserDomainMask) as! [NSURL]
if let applicationSupportURL = urls.last {
    fileManager.createDirectoryAtURL(applicationSupportURL, withIntermediateDirectories: true, attributes: nil, error: nil)
}

这样做是因为createDirectoryAtURL使用withIntermediateDirectories: true如果不存在,只创建文件夹.

Answer 4

一个班轮 - 如有必要也将创建：

[[NSFileManager defaultManager] URLForDirectory:NSApplicationSupportDirectory inDomain:NSUserDomainMask appropriateForURL:nil create:YES error:nil]