Ios 从url下载文件并保存到iPhone上的资源

是否可以通过编程方式将文件（即sqlite数据库文件）从Internet下载到iPhone应用程序中，以便以后在应用程序中使用

我正在尝试使用

NSURLConnection

，但无法保存文件

下面是我正在尝试的示例代码：

- (void)viewDidLoad
{
    [super viewDidLoad];

    NSString *file = [NSString stringWithFormat:@"http://en.wikipedia.org/wiki/Text_file"];
    NSURL *fileURL = [NSURL URLWithString:file];

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

- (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:@"%@/blah.text", [dirArray objectAtIndex:0]];

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

---

什么是文件数据？它是如何定义和初始化的

  fileData = [NSMutableData data];

应在以下位置之后：

NSURLConnection *conn = [NSURLConnection connectionWithRequest:req delegate:self];

您必须初始化文件数据并按照内存管理规则保留它

---

试试我的答案。它起作用了

您需要使用

stringByAppendingPathComponent

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *writableDBPath = [documentsDirectory stringByAppendingPathComponent:@"bookdb.sql"];

---

在方法中尝试此代码并执行

NSURL *url=[NSURL URLWithString:@"http://en.wikipedia.org/wiki"];

NSData *dbFile = [[NSData alloc] initWithContentsOfURL:url];   

NSString *resourceDocPath = [[NSString alloc] initWithString:[[[[NSBundle mainBundle]  resourcePath] stringByDeletingLastPathComponent]stringByAppendingPathComponent:@"Documents"]];

NSString *filePath = [resourceDocPath stringByAppendingPathComponent:@"Text_file.txt"];  

[dbFile writeToFile:filePath atomically:YES];

---

这对你很有用

NSString *stringURL = @"http://www.somewhere.com/thefile.png";
NSURL  *url = [NSURL URLWithString:stringURL];
NSData *urlData = [NSData dataWithContentsOfURL:url];
if ( urlData )
{
  NSArray       *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
  NSString  *documentsDirectory = [paths objectAtIndex:0];  

  NSString  *filePath = [NSString stringWithFormat:@"%@/%@", documentsDirectory,@"filename.png"];
  [urlData writeToFile:filePath automically:YES];
}

---

请注意，这是一个

writeToFile

方法，它是同步的，因此它将停止/阻止您的UI。

这里到底是什么失败？如果（[self.fileData writeToFile:path options:NSAtomicWrite error:nil]==NO）{NSLog（@“writeToFile error”）；}我得到了“writeToFile error”，我想从Internet下载数据库（存储在某台服务器上的某个地方）没关系，您仍然需要扩展~Yes，它在头文件中是这样定义的。我在上面的viewDidLoad中没有看到它。它在哪里初始化？？？fileData=[NSMutableData]；按照我在回答（viewDidLoad）中所述初始化fileData，它就会工作。您需要：fileData=[[NSMutableData alloc]initWithLength:0]；或fileData=[NSMutableData]；在-（void）viewDidLoad中。选择此作为答案。重新询问有关数据库的问题。指向文档目录的URL以这种方式更好->NSURL*documentsDirectory=[[[NSFileManager默认管理器]URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask]lastObject]；您可以这样[URL path]来获取路径