ios - 如何打开 performselectorinbackground 功能 Ios

Question

我正在尝试使用performselectorinbackground，但它没有运行。有人告诉我，应用程序设置中有一项检查允许 ios 中的后台任务，但我找不到该检查。因此，请告诉我如何通过将检查添加到应用程序设置 plist 文件来打开后台任务功能。我正在使用此代码进行后台任务。

@implementation NetworkHandler
@synthesize delegate=_delegate;

- (void)sendServerCall:(NSDictionary *)data {
    [self performSelectorInBackground:@selector(onBackground:) withObject:data];
}

-(void)onBackground:(NSDictionary *)data
{
    @try{
        _methodNameResult=[NSString stringWithFormat:@"%@%@", [data objectForKey:Dictionary_Keys_Method],Dictionary_Keys_ResultVal];
        _delegateKey=[[data objectForKey:Dictionary_Keys_Delegate] integerValue];
        NSURL *serviceUrl = [NSURL URLWithString:[data objectForKey:Dictionary_Keys_WebServiceUrl]];
        NSMutableURLRequest *theRequest = [NSMutableURLRequest requestWithURL:serviceUrl];
        NSString *msgLength = [NSString stringWithFormat:@"%lu",(unsigned long)[[data objectForKey:Dictionary_Keys_SopaMessage] length]];
        [theRequest addValue:@"text/xml" forHTTPHeaderField:@"Content-Type"];
        [theRequest addValue:[NSString stringWithFormat:@"%@%@", [data objectForKey:Dictionary_Keys_WebServiceNameSpace],[data objectForKey:Dictionary_Keys_Method]] forHTTPHeaderField:@"SOAPAction"];
        [theRequest addValue: msgLength forHTTPHeaderField:@"Content-Length"];
        [theRequest setHTTPMethod:@"POST"];
        [theRequest setHTTPBody:[[data objectForKey:Dictionary_Keys_SopaMessage] dataUsingEncoding:NSUTF8StringEncoding]];
        NSURLConnection *theConnection = [[NSURLConnection alloc]initWithRequest:theRequest delegate:self ];
        if ( theConnection ){
            _conWebData= [NSMutableData data];
        }
        else
        {
            [self performSelectorOnMainThread:@selector(onMain:) withObject:[[NSDictionary alloc]init] waitUntilDone:true];
        }
    }@catch (NSException *exception) {
        [CommonMethods logException:@"NetworkHandler - onBackground\n" :exception :@"NetworkHandler"];
        [self performSelectorOnMainThread:@selector(onMain:) withObject:[[NSDictionary alloc]init] waitUntilDone:true];
    }
}

-(void)onMain:(NSDictionary *)data
{
    [self performSelectorOnMainThread:@selector(onMain:) withObject:[[NSDictionary alloc]init] waitUntilDone:true];
}

-(void)connection:(NSURLConnection*)connection didReceiveResponse:(NSURLResponse*)response{
    @try{
        [_conWebData setLength:0];
    }@catch (NSException *exception) {
        [CommonMethods logException:@"NetworkHandler - didReceiveResponse\n" :exception :@"NetworkHandler"];
        [self performSelectorOnMainThread:@selector(onMain:) withObject:[[NSDictionary alloc]init] waitUntilDone:true];
    }
}

-(void)connection:(NSURLConnection*)connection didReceiveData:(NSData*)data{
    @try{
        [_conWebData appendData:data];
    }@catch (NSException *exception) {
        [CommonMethods logException:@"NetworkHandler - didReceiveData\n" :exception :@"NetworkHandler"];
        [self performSelectorOnMainThread:@selector(onMain:) withObject:[[NSDictionary alloc]init] waitUntilDone:true];
    }
}

-(void)connection:(NSURLConnection*)connection didFailWithError:(NSError*)error{
    @try{
        [self performSelectorOnMainThread:@selector(onMain:) withObject:[[NSDictionary alloc]init] waitUntilDone:true];
    }@catch (NSException *exception) {
        [CommonMethods logException:@"NetworkHandler - didFailWithError\n" :exception :@"NetworkHandler"];
        [self performSelectorOnMainThread:@selector(onMain:) withObject:[[NSDictionary alloc]init] waitUntilDone:true];
    }
}

-(void)connectionDidFinishLoading:(NSURLConnection*)connection{
    @try{
        NSString*theXML = [[NSString alloc]initWithBytes: [_conWebData mutableBytes]length:[_conWebData length]encoding:NSUTF8StringEncoding];
        NSError *parseError = nil;
        NSDictionary *data=[[NSDictionary alloc]init];
        data=[XMLReader dictionaryForXMLString:theXML error:&parseError];
        [self performSelectorOnMainThread:@selector(onMain:) withObject:data waitUntilDone:true];
    }@catch (NSException *exception) {
        [CommonMethods logException:@"NetworkHandler - connectionDidFinishLoading\n" :exception :@"NetworkHandler"];
        [self performSelectorOnMainThread:@selector(onMain:) withObject:[[NSDictionary alloc]init] waitUntilDone:true];
    }
}

我不知道，但我认为我不需要在这里执行performSelectorInbackground，因为我认为我在这里执行服务器调用，而performSelectorInbackground基本上用于内部计算或从内部数据库获取数据时使用，所以不需要使用performSelectorInbackground，但如果否则，如果我需要使用 PerformSelectorInbackground 那么我们如何启用此功能并自动启用？？？

Answer 1

performSelectorInBackground 和performSelectorOnMainThread 分别与在后台和主线程上执行操作(执行函数)有关。这两个函数都与线程概念相关。

performSelectorInBackground，在后台线程上执行选择器内的指令。当应用程序处于前台状态时，这会起作用。

如果您想在应用程序处于后台状态时执行任何任务，那么在这种情况下，performSelectorInBackground 将不起作用。

如果您想在后台执行任务，那么以下链接可能会很有用 -

https://developer.apple.com/library/ios/documentation/iPhone/Conceptual/iPhoneOSProgrammingGuide/BackgroundExecution/BackgroundExecution.html

http://www.raywenderlich.com/29948/backgrounding-for-ios