Question

我无法使NSMetadataQueryDidUpdateNotification正常工作。被困了几天。下面的代码中是否有异常。

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0ul), ^{


    NSString* filePattern = [NSString stringWithFormat:@"*.%@", @"*"];

        NSMetadataQuery *aQuery = [[NSMetadataQuery alloc] init];
        aQuery.predicate = [NSPredicate predicateWithFormat: @"%K LIKE %@", NSMetadataItemFSNameKey, filePattern];

        [aQuery setSearchScopes:@[NSMetadataQueryUbiquitousDataScope]];
        [aQuery setValueListAttributes:@[NSMetadataUbiquitousItemPercentDownloadedKey, NSURLUbiquitousItemDownloadingStatusKey,NSURLUbiquitousItemIsDownloadingKey,NSURLUbiquitousItemDownloadRequestedKey]];

        _query = aQuery;

        [[NSNotificationCenter defaultCenter] addObserver:self
                                                                 selector:@selector(liveUpdate:)
                                                                     name:NSMetadataQueryDidUpdateNotification
                                                                   object:aQuery];

        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(initalGatherComplete:)                                                                                          name:NSMetadataQueryDidFinishGatheringNotification object:aQuery];

        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(gatherProgress:)                                                                                          name:NSMetadataQueryGatheringProgressNotification object:aQuery];

        [aQuery enableUpdates];

         dispatch_async(dispatch_get_main_queue(), ^{

        [aQuery startQuery];


        });


        });

Answer 1

希望这有助于你

尝试使用此代码替换有关通知的内容元数据查询应该在主队列上启动，你做对了：）

    [[NSNotificationCenter defaultCenter] addObserver:self  
selector:@selector(liveUpdate:) 
name:NSMetadataQueryDidUpdateNotification 
object:aQuery];

    [[NSNotificationCenter defaultCenter] addObserver:self
selector:@selector(initalGatherComplete:)
name:NSMetadataQueryDidFinishGatheringNotification 
object:aQuery];

这是处理收集通知的示例

- (void)initialGatherComplete:(NSNotification*)notification
{
      //process here.
}

Answer 2

解决方案是强烈引用通知块

    _notifqueryDidUpdate = [[NSNotificationCenter defaultCenter]addObserverForName:NSMetadataQueryDidUpdateNotification object:aQuery queue:[NSOperationQueue mainQueue] usingBlock:^(NSNotification * _Nonnull note) {

                                [self liveUpdate:note];

                            }];

NSMetadataQueryDidUpdateNotification无法使其正常工作。包含代码片段

2 个答案: