如何检测UISearchBar/UITextField的输入暂停？

Question

我有以下UISearchbar代码:

- (void)searchBar:(UISearchBar *)searchBar textDidChange:(NSString *)searchText
{
    [UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
    NSString* endpoint =[NSString stringWithFormat:@"http://www.someurl/",
                         [searchText stringByReplacingOccurrencesOfString:@" " withString:@"+"]];
    NSURL* url = [NSURL URLWithString:endpoint];
    NSURLRequest* request = [NSURLRequest requestWithURL:url];
    GTMHTTPFetcher* myFetcher = [GTMHTTPFetcher fetcherWithRequest:request];
    [myFetcher beginFetchWithDelegate:self didFinishSelector:@selector(searchResultsFetcher:finishedWithData:error:)];
}

我希望在输入暂停后发送此请求,并在每次命中一个字符时重置计时器.我怎样才能做到这一点？

Answer 1

它不必使用NSTimer.

- (void)searchBar:(UISearchBar *)searchBar textDidChange:(NSString *)searchText
        {
           [NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(request) object:nil];

          //.....

           [self performSelector:@selector(request) withObject:nil afterDelay:yourpausetime];

        }

Answer 2

在该textDidChange方法中创建一个NSTimer,比如说值2秒.如果计时器已存在,则使组合器无效并重新创建.(未经测试的代码:)

- (void)searchBar:(UISearchBar *)searchBar textDidChange:(NSString *)searchText
{
    if (myTimer) {
        if ([myTimer isValid]) { [myTimer invalidate]; }
        [myTimer release], myTimer = nil;
    }
    myTimer = [[NSTimer scheduledTimerWithTimeInterval:2.0 target:self selector:@selector(userPaused:) userInfo:nil repeats:NO] retain];
}

当用户停止键入2秒时,将调用-userPaused:并且您的计时器将自动失效(尽管不是nil).当用户再次开始键入时,将设置新的计时器.