objective-c - IOS - 按顺序加载本地文件

Question

我在应用程序的 Document 文件夹中有一个图像列表。我想按创建日期的顺序加载图像。我怎样才能做到这一点 ？

Answer 1

此代码将按照创建顺序枚举您的文档目录中的所有文件：

查看代码中的注释以了解发生了什么。

NSFileManager *fm = [NSFileManager defaultManager];
NSString *doc = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
NSError *err;
// Get all files with their creation date
NSArray *files = [fm contentsOfDirectoryAtURL:[[NSURL alloc] initFileURLWithPath:doc isDirectory:YES]
    includingPropertiesForKeys:[NSArray arrayWithObject:NSURLCreationDateKey]
    options:0
    error:&err];
// Using file's URL as the key, store creation date as the value
NSMutableDictionary *urlWithDate = [NSMutableDictionary dictionaryWithCapacity:files.count];
for (NSURL *f in files) {
    NSDate *creationDate;
    if ([f getResourceValue:&creationDate forKey:NSURLCreationDateKey error:&err]) {
        [urlWithDate setObject:creationDate forKey:f];
    }
}
// Sort the dictionary on the value, which is the creation key
for (NSURL *f in [urlWithDate keysSortedByValueUsingComparator:^NSComparisonResult(id obj1, id obj2) {
    return [obj1 compare:obj2];
}]) {
    // Check if the file is an image. Load if it is an image, otherwise skip.
    NSLog(@"%@", f);
}

Answer 2

我会看一下：Getting a list of files in a directory with a glob

特别是 NSFileManager。您可以查看文件的属性。从那里您很可能可以使用 NSPredicate 进行排序。