Question

我不确定暂停下载的最佳方法是什么。我之前已经在堆栈上看过这个问题，但似乎没有达到我想要的结果。例如：我理解AppDelegate内部，如果手机上有电话，则会调用 - (void)applicationWillResignActive:(UIApplication *)application。我的应用程序成功下载数据库以正常运行至关重要。这是我用来下载数据库的代码：

NSString * urlDb = [NSString stringWithFormat：@＆＃34; someURl＆＃39;];

//---Create URL from where DB has to be download-----
NSURL *url = [NSURL URLWithString:urlDb];

NSError *error = nil;
NSData *data = [NSData dataWithContentsOfURL:url options:0 error:&error];

暂停下载可能并不重要，例如AT＆amp; T，但是Verizon的用户无法同时进行通话和下载。任何帮助将不胜感激。谢谢！

Answer 1

如果您想要暂停/恢复功能，那么您必须使用旧的NSURLConnection，并实现所有必需的委托方法，或者您可以使用新的NSURLSession API。以下是NSURLConnection的基本实现：

@property NSFileHandle *fileHandle;
@property NSURLConnection *connection;

// start download

- (IBAction)downloadButtonPressed
{
    NSURL *url = [NSURL URLWithString:@"myUrl"];
    NSURLRequest *dataRequest = [NSURLRequest requestWithURL:url];
    self.connection = [NSURLConnection connectionWithRequest:dataRequest delegate:self];
    [connection start];
}

实施委托方法

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    self.fileHandle = [NSFileHandle fileHandleForWritingAtPath:@“pathToYourFile”];
    [self.fileHandle seekToEndOfFile];
}

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

如果你想暂停 - 只需取消这样的连接：

[self.connection cancel];

然后你可以这样恢复：

- (void)resumeDownload
{
    NSURL *url = [NSURL URLWithString:@"myUrl"];
    NSMutableURLRequest *dataRequest = [NSMutableURLRequest requestWithURL:url];
    NSDictionary *fileAttributes = [[NSFileManager defaultManager] attributesOfItemAtPath:pathToYourFile error:&attributesError];
    NSNumber *fileSizeNumber = [fileAttributes objectForKey:NSFileSize];
    NSString *bytesRangeHeader = [NSString stringWithFormat:@"bytes=%lld-", [fileSizeNumber longLongValue];
    [_request setValue:bytesRangeHeader forHTTPHeaderField:@"Range"];
    self.connection = [NSURLConnection connectionWithRequest:dataRequest delegate:self];
    [connection start];
}

在objective-c中暂停下载

1 个答案: