Iphone 委托并执行SelectorOnMainThread

我对这两个词的用法有点困惑

我有一个后台线程，负责下载数据并将其应用到iOS设备内的核心数据数据库

后台线程中的代码调用共享实例类ProgressController来更新UI上的进度（我知道它在主线程中运行）。ProgressController然后有一个委托，该委托由顶部的视图控制器分配

除了后台线程启动后UI不会更新之外，一切正常。我知道正在调用委托，因为我有NSLogs，其中包含正在传递的文本

现在我读到我应该使用performSelectorOnMainThread，但考虑到委托正在触发，这似乎是多余的

我应该改用performSelectorOnMainThread，而不使用委托吗

我错过什么了吗

如果有人能解释，我会非常感激

谢谢

克里斯

在后台线程中

progressController = [ProgressController sharedInstance];
[progressController open];

在ProgressController.h中

#import <Foundation/Foundation.h>

@protocol ProgressControllerDelegate 
@required
- (void) displayProgress:(NSString *)text;
- (void) showProgress;
- (void) hideProgress;

@end

@interface  ProgressController : NSObject {

    NSString    *currentProgress;
    BOOL        progressOnDisplay;
    id          delegate;
}

+ (ProgressController *)sharedInstance;

@property (nonatomic) BOOL  progressOnDisplay;
@property (nonatomic, assign) id delegate;

-(void) open;
-(void) updateProgress:(NSString *)text;
-(void) reDisplayProgress;
-(void) close;

@end

视图控制器内部

- (void)viewDidLoad {
    [super viewDidLoad];

    progressController = [ProgressController sharedInstance];
    progressController.delegate = self;
    [progressController reDisplayProgress]; // In case progress has been updated prior to the view load

}

// Delegate method to show Progress Label
- (void) showProgress {
    progressView.hidden = FALSE;    

}

// Delegate method to display specific text in Progress label
- (void) displayProgress:(NSString *)text {
    [progressLabel setText:text];
    [progressView setNeedsDisplay];

    DLog(@"Reporting -  %s", [text UTF8String]);  // I can see that this is firing successfully

}

// Delegate method to hide Progress Label
- (void) hideProgress {
    progressView.hidden = TRUE;

}

---

您应该使用NSURLConnection类异步下载数据，然后可以使用其委托方法更新UI

请参阅本守则-

    // create the URL
    NSURL *postURL = [NSURL URLWithString:@"http://twitpic.com/api/uploadAndPost"];

    // create the connection
    NSMutableURLRequest *postRequest = [NSMutableURLRequest requestWithURL:postURL
                                                               cachePolicy:NSURLRequestUseProtocolCachePolicy
                                                           timeoutInterval:30.0];

    // change type to POST (default is GET)
    [postRequest setHTTPMethod:@"POST"];
NSURLConnection *theConnection = [[NSURLConnection alloc] initWithRequest:postRequest delegate:self];

    if( theConnection )
    {
        webData = [[NSMutableData data] retain];
    }

委托方法-

-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    [webData setLength: 0];
}
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
// update your UI here.. 
    [webData appendData:data];
}
-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    NSLog(@"ERROR with theConenction");
    [connection release];
    [webData release];
}
-(void)connectionDidFinishLoading:(NSURLConnection *)connection
{
//  your data downloaded completely.. do you code here.. 

}

---

委托方法本身与线程没有特定的关系。它只是一个对象向另一个对象发送消息。如果该委托方法恰好在后台线程上被调用，那么任何UI交互都必须在主线程上完成

有关更多信息，请参阅文档：

某些对象将委托调用与特定线程相关联。例如，NSURLConnection的

+connectionWithRequest:delegate:

，其文档说明：

发送给委托的消息将在调用此方法的线程上发送。要使连接正常工作，调用线程的运行循环必须在默认运行循环模式下运行

---

因此，简而言之，是的，可以同时使用委托方法和

performSelectorOnMainThread

来更新UI。这样做没有错。

插入的代码显示您直接从后台线程调用委托方法。要在主线程上执行GUI工作（您应该这样做），您需要在调用委托的方法时直接使用

performSelectorOnMainThread:

，或者在委托方法本身中使用。如果您想在这些更新过程中停止后台线程，您可以使用带有

waitUntilDone:YES

的变体。请在后台线程中显示调用ProgressController方法的代码。谢谢Eiko。例如，在委托（ProgressController.m）中，应该[self.delegate displayProgress:currentProgress]；成为[self.delegate:currentProgress]执行SelectorOnMainThread:@selector（displayProgress:）with object:currentProgress waitUntilDone:NO]？它应该类似于[self.delegate performselectornmainthread:@selector（displayProgress:）withObject:currentProgress]；（未经测试，仅在此处键入）你是明星Eiko。非常感谢。我在委托中需要的行的格式为[self.delegate performSelectorOnMainThread:@selector（displayProgress:）withObject:currentProgress waitUntilDone:NO]；正如您所说，这意味着从主线程调用委托，UI现在更新。现在都在工作。

    // create the URL
    NSURL *postURL = [NSURL URLWithString:@"http://twitpic.com/api/uploadAndPost"];

    // create the connection
    NSMutableURLRequest *postRequest = [NSMutableURLRequest requestWithURL:postURL
                                                               cachePolicy:NSURLRequestUseProtocolCachePolicy
                                                           timeoutInterval:30.0];

    // change type to POST (default is GET)
    [postRequest setHTTPMethod:@"POST"];
NSURLConnection *theConnection = [[NSURLConnection alloc] initWithRequest:postRequest delegate:self];

    if( theConnection )
    {
        webData = [[NSMutableData data] retain];
    }

-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    [webData setLength: 0];
}
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
// update your UI here.. 
    [webData appendData:data];
}
-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    NSLog(@"ERROR with theConenction");
    [connection release];
    [webData release];
}
-(void)connectionDidFinishLoading:(NSURLConnection *)connection
{
//  your data downloaded completely.. do you code here.. 

}