递归思路：

- (void)showAllFileWithPath:(NSString *) path {
    NSFileManager * fileManger = [NSFileManager defaultManager];
    BOOL isDir = NO;
    BOOL isExist = [fileManger fileExistsAtPath:path isDirectory:&isDir];
    if (isExist) {
        if (isDir) {
            NSArray * dirArray = [fileManger contentsOfDirectoryAtPath:path error:nil];
            NSString * subPath = nil;
            for (NSString * str in dirArray) {
                subPath  = [path stringByAppendingPathComponent:str];
                BOOL issubDir = NO;
                [fileManger fileExistsAtPath:subPath isDirectory:&issubDir];
                [self showAllFileWithPath:subPath];
            }
        }else{
            NSString *fileName = [[path componentsSeparatedByString:@"/"] lastObject];
            if ([fileName hasSuffix:@".png"]) {
                //do anything you want
                [self.imageArray addObject:fileName];
            }else if([fileName hasSuffix:@".mv"]){
                    [self.imageArray addObject:fileName];
            }
        }
    }else{
        NSLog(@"this path is not exist!");
    }
}