Question

当应用程序通过HTTP Post与服务器通信时，如何显示AlertView？我当前的代码无法正常工作。

基本上，一个AlertView要求确认一些事情。如果确认，则会发生以下代码：

-(void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
{//this is for when the person clicks OK
    NSString *title = [alertView buttonTitleAtIndex:buttonIndex];
    if([title isEqualToString:@"OK"])
    {
        //do alert
        UIAlertView *waitAlert = [[UIAlertView alloc] initWithTitle:@"Communicating with Server..."  
                                                            message:nil 
                                                           delegate:nil  
                                                  cancelButtonTitle:nil  
                                                  otherButtonTitles:nil];  
        UIActivityIndicatorView *loading = [[UIActivityIndicatorView alloc] initWithFrame:CGRectMake(125, 50, 30, 30)];
        loading.activityIndicatorViewStyle = UIActivityIndicatorViewStyleWhiteLarge;
        [waitAlert addSubview:loading];
        [loading startAnimating];
        [waitAlert show];

        //communicate with Server
        RetailTransaction *retailTransaction = [[RetailTransaction alloc]init];
        ServerConnection *serverConnection = [[ServerConnection alloc]init];
        NSData *serverResponse = [serverConnection postData:[retailTransaction xmlToXml:
                                                             note.text:
                                                             pin.text:
                                                             total.text]];
        NSString *serverResponseString = [[NSString alloc] initWithData:serverResponse
                                                               encoding:NSUTF8StringEncoding];
        NSLog(@"Server Responded with: %@", serverResponseString);

这个方法有更多的代码，但这会得到基本的东西。 waitAlert甚至在应用程序与服务器通信之后才会出现，此时它只会瞬间出现。有谁知道为什么会这样？它应该在与服务器通信之前出现。提前致谢。

Answer 1

将此部分移动到另一个函数并在后台线程中运行该函数。

        //communicate with Server
    RetailTransaction *retailTransaction = [[RetailTransaction alloc]init];
    ServerConnection *serverConnection = [[ServerConnection alloc]init];
    NSData *serverResponse = [serverConnection postData:[retailTransaction xmlToXml:
                                                         note.text:
                                                         pin.text:
                                                         total.text]];
    NSString *serverResponseString = [[NSString alloc] initWithData:serverResponse
                                                           encoding:NSUTF8StringEncoding];
    NSLog(@"Server Responded with: %@", serverResponseString);

....

警告视图在调用之前未显示的原因是主线程被挂起。

Answer 2

使用ASIHTTPRequest

非常简单

-(void)sendMessage{
   NSString *url = @"http://www.your-server.com";
    ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:[NSURL URLWithString:url]];
    [request setDelegate:self];
    [request startAsynchronous];
    [alertView show];
}

-(void)requestFinished:(ASIHTTPRequest *)request{
     [alertView hide];
}


-(void)requestFailed:(ASIHTTPRequest *)request{
    NSLog(@"%@", [[request error] description]);
}

在这种情况下，您可以从启动警报的位置调用[self sendMessage]，但我对其进行了简化。关键是异步执行请求。

此示例不执行POST，但也可以使用ASIHTTPRequest。

请与服务器通话时等待AlertView

2 个答案: