这很奇怪；我有一个像这样的异步连接：
NSString *url=[NSString stringWithFormat:@"http://www.whatever.com/file"];
NSURL *url2=[NSURL URLWithString:url];
NSURLRequest *req=[[NSURLRequest alloc] initWithURL:url2];
NSURLConnection*con=[[NSURLConnection alloc] initWithRequest:req delegate:self];
[req release];
if(con){
NSMutableData *data=[[NSMutableData alloc] init];
self.receivedData=data;
[data release];
}
else {
UIAlertView*alert=[[UIAlertView alloc] initWithTitle:@"Error!" message:@"Unable to connect to server." delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
[alert show];
[alert release];
}
然后我有一堆标准的委托方法：
-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{
[receivedData setLength:0];
}
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{
[receivedData appendData:data];
}
-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error{
[connection release];
self.receivedData=nil;
UIAlertView*alert=[[UIAlertView alloc] initWithTitle:@"This app requires Internet" message:[NSString stringWithFormat: @"Connection failed.\n Please exit and check your\nInternet access."] delegate:self cancelButtonTitle:@"OK" otherButtonTitles: nil];
[alert show];
[alert release];
}
-(void) connectionDidFinishLoading:(NSURLConnection *)connection{
NSString *payload=[[NSString alloc] initWithData:receivedData encoding:NSUTF8StringEncoding];
self.downloaded=nil;
self.downloaded=payload;
[payload release];
[connection release];
self.receivedData=nil;
NSLog(@"This will display if connectionDidFinishLoading runs.");
}
最后的 NSLog 正在运行，即使该文件不在服务器上。为什么？我不希望它加载任何东西，而是导致错误和警报视图。
这些方法一开始看起来很清楚，但这里肯定发生了一些我没有了解异步连接的事情。