Queue自定义NSOperation，并发需注意

OperationQueue添加，   自定义继承自NSOperation的子类，

若开启并发，

重复执行5次左右，会卡在

NSOperation类：

- (void)finish {    //结束线程用到

    [selfwillChangeValueForKey:@"isExecuting"];  

    [selfwillChangeValueForKey:@"isFinished"];  

    

    executing = NO;  

    finished = YES;  

 

    [selfdidChangeValueForKey:@"isExecuting"];  

    [selfdidChangeValueForKey:@"isFinished"];  

}   

- (id)initWithURL:(NSString*)url delegate:(id<downloadFinishDelegate>)delegate//delegate是资料下载结束的回调

{

    if(self=[superinit])

    {

        executing = NO; 

        finished = NO;  

        

        _webReachable=[WebConnectionWebConnect];

        self.delegate=delegate;

        _enc =CFStringConvertEncodingToNSStringEncoding(kCFStringEncodingGB_18030_2000);  

        _request=[[NSURLRequestrequestWithURL:[NSURLURLWithString:[url stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding]]]retain];

        self.XMLData=[NSMutableData data];

    }

    return self;

}

 

- (void)start   在线程队列中重写start，线程会叠加，卡死

{

    [selfwillChangeValueForKey:@"isExecuting"]; 

    executing = YES;  

    [selfdidChangeValueForKey:@"isExecuting"];  

    

    //if(![self isCancelled])

    if([NSURLConnection canHandleRequest:_request]&&_webReachable)

    {

        _connection=[[NSURLConnection  connectionWithRequest:_requestdelegate:self] retain];

        while (_connection!=nil) { 

            [[NSRunLoop  currentRunLoop]runMode:NSDefaultRunLoopMode  beforeDate:[NSDatedistantFuture]];

        }

    }

    else

    {

        UIAlertView *alert=[[UIAlertView alloc]initWithTitle:@"无网络连接1" message:@"请检查网络" delegate:nil cancelButtonTitle:@"确定" otherButtonTitles:nil, nil];

        [alert show];

        [alert release];

    }

}

- (BOOL)isFinished   //自定义operation时候用到

{

    return  finished;

}

- (BOOL)isConcurrent

{

    returnYES;

}

- (BOOL)isExecuting

{

    return  executing;

}

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response

{

    [self.XMLData setLength:0];

} 

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data

{

    [self.XMLData appendData:data];

}

 

- (void)connectionDidFinishLoading:(NSURLConnection *)connection

{

　　[self.connection release];  

　　self.connection = nil;

self.lastLoadXMLData=[[_XMLDatacopy]autorelease];

    //if([_delegate respondsToSelector:@selector(downloadFinish)])

    if([_delegate conformsToProtocol:(@protocol(downloadFinishDelegate))])

    {

        [_delegatedownloadFinish:self.lastLoadXMLData];

    }

    [self finish];

}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error

{

    NSLog(@"error:%@",[error localizedDescription]);

    [self finish];

}

回调类：

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath

{

    self.tableView.UserInteractionEnabled=NO;

    DownloadOperation *downloadOperation=[[DownloadOperationalloc]initWithURL:@"http://www.bart.gov/dev/eta/bart_eta.xml"delegate:self];

    //[queue cancelAllOperations];

    [queue addOperation:downloadOperation];

    //添加到queue中,并重写start方法，线程会叠加，卡死。

　　//暂时解决方法：1  不重写start(),finish() 和executing()方法，只重写main方法。

　　　　　　　　　　2 需重写start、finish和 executing方法

一般加入线程队列，不需开启并发concurrent.   开启并发则不加入队列，用 [operation start]

    [downloadOperation release];

    NSLog(@"%i",[queueoperationCount]);

    [selftransitionView];

}

 

 

修改后回调类：

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath

{

    self.tableView.UserInteractionEnabled=NO;

    DownloadOperation *downloadOperation=[[DownloadOperationalloc]initWithURL:@"http://www.bart.gov/dev/eta/bart_eta.xml"delegate:self];

   

    [downloadOperation start];

  [downloadOperation release];

/*需重载

- (BOOL)isFinished；

- (BOOL)isConcurrent；

- (BOOL)isExecuting；

并设定开关条件

执行：

 

[self willChangeValueForKey:@"isExecuting"];
executing = YES;
[self didChangeValueForKey:@"isExecuting"];

结束：

[self finish];

*/

    [self  transitionView];

}