ios - 检查目录中的文本文件是否直接显示

Question

我正在开发一个 iOS 应用程序。我从一个 URL 下载文本文件并将其保存到一个目录中，但我在该目录中找不到该文件，因此代码再次下载它。如何检查文件？

if ([[NSFileManager defaultManager] fileExistsAtPath:localfile]) {
         content = [NSString stringWithContentsOfFile:localfile
                                            encoding:NSUTF8StringEncoding
                                               error:NULL];
    }else
    {
        NSURL* url = [NSURL URLWithString:@"http://webapp.opaxweb.net/books/gurugranthsahib.txt"];

    NSArray* pathArray = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,
                                                             NSUserDomainMask, YES);
    NSString* documentsDir = [pathArray objectAtIndex:0];
    localfile =[documentsDir stringByAppendingPathComponent:@"data"];
        NSData* data = [NSData dataWithContentsOfURL:url];
    [data writeToFile:localfile atomically:YES];
    content = [NSString stringWithContentsOfFile:localfile
                                        encoding:NSUTF8StringEncoding
                                         error:NULL];
}
_textfield.text=content;

Answer 1

您的文本数据相当大，因此您应该使用 nsurl 连接!您的代码完全正确，但这是一个更好的方法。

    - (void)viewDidLoad
    {
        [super viewDidLoad];
        self.fileName = @"Data";
        self.fileData = [NSMutableData data];
        [self checkFileExitsorNOt];
    }

    - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
    {
        [self.fileData setLength:0];
        self.totalFileSize = [NSNumber numberWithLongLong:[response expectedContentLength]];
    }

    - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
    {
            [self.fileData appendData:data];        
    }

    - (void)connectionDidFinishLoading:(NSURLConnection *)connection
    {
        NSArray *dirArray = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,    NSUserDomainMask, YES);
        NSLog(@"%@", [dirArray objectAtIndex:0]);

        NSString *path = [NSString stringWithFormat:@"%@/%@", [dirArray objectAtIndex:0],self.fileName];

        if ([self.fileData writeToFile:path options:NSAtomicWrite error:nil] == NO) {
            NSLog(@"writeToFile error");
        }
        else {
            NSLog(@"Written!");
        }
    }

-(void) checkFileExitsorNOt
{
    NSArray *dirArray = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,    NSUserDomainMask, YES);
    NSLog(@"%@", [dirArray objectAtIndex:0]);

    NSString *path = [NSString stringWithFormat:@"%@/%@", [dirArray objectAtIndex:0],self.fileName];

    if ([[NSFileManager defaultManager] fileExistsAtPath:path]) {
        NSString  *cont = [NSString stringWithContentsOfFile:localfile
                                                    encoding:NSUTF8StringEncoding
                                                       error:NULL];
        NSLog(@"Content from file : %@",cont);
    }
    else
    {
        NSString *file = [NSString stringWithFormat:@"http://webapp.opaxweb.net/books/gurugranthsahib.txt"];
        NSURL *fileURL = [NSURL URLWithString:file];

        NSURLRequest *req = [NSURLRequest requestWithURL:fileURL];
        NSURLConnection *conn = [NSURLConnection connectionWithRequest:req delegate:self];
    }

}