道歉，我想不出更好的方式来描述我的 应用程序的功能。
我在这个主题上发现了很多帖子，也在parse.com的旧档案中。然而，这对我不起作用。创建由 PFQuery.findObjects 触发的 PFQuery 实例（但在后台线程上运行）后，我无法在请求过程中取消它。 / p>
场景：基本上我有一个连接到Parse的应用。我在DataDisplay屏幕上显示了超过100条记录的数据，当用户点击后退按钮时它有一个后退按钮，如果 PFQuery.findObjects 仍然在后台线程上运行它，那么我必须取消它
我尝试在viewWillDisappear中插入 PFQuery.cancel ，但它无法停止，并且由于这些DataDisplay屏幕的 dealloc 方法未被调用。
我的代码，包含它可能会有所帮助：
- (void)loadANDSortingSongInformationWS {
if(ISINTERNET) {
if(self.isShowLoadingForSkipSong)//Not Showing the activity indicator
self.isShowLoadingForSkipSong = NO;
else if(self.isFirstLoad || self.isAddPullToRefreshLikeSong)//Showing the indicator
[self showHideLoading:YES];
PFQuery *query = [PFQuery queryWithClassName:[UserPlaylistSongs parseClassName]];
[query setLimit:1000];
[query orderByDescending:@"createdAt"];
[query whereKey:@"Playlist" equalTo:self.playlistInfo];
[query includeKey:@"Playlist"];
[query includeKey:@"Song"];
[query includeKey:@"AddedBy"];
[query includeKey:@"Host"];
__weak typeof(self) weakSelf = self;
[self.opearation addOperationWithBlock:^{
[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
if (objects.count == 0) {//No Songs Found
//If there is no records
dispatch_async(dispatch_get_main_queue(), ^{
[weakSelf showHideLoading:NO];
if(weakSelf.isFirstLoad || weakSelf.isAddPullToRefreshLikeSong) {//Problem while user pull to refresh when there is no song
[KSToastView ks_showToast:@"No Songs Found." duration:1.0f];
}
});
}
else {//Songs Found
dispatch_async(dispatch_get_main_queue(), ^{
NSMutableArray *arrParseSongList = [[NSMutableArray alloc] init];
__block NSInteger getTotalObjectsCount = 0;
for(NSInteger i=0; i<objects.count; i++) {
SongListInfo *songListData = [[SongListInfo alloc] init];
songListData.userPlaylistInfo = objects[i];
songListData.totLikes = [objects[i][@"Likes"] integerValue];
songListData.totDisLikes = [objects[i][@"Dislikes"] integerValue];
songListData.isPlaying = [objects[i][@"PlayingStatus"] boolValue];
songListData.songInfo = objects[i][@"Song"];
songListData.hostInfo = objects[i][@"Host"];
songListData.addedInfo = objects[i][@"AddedBy"];
songListData.playlistInfo = objects[i][@"Playlist"];
songListData.alreadyPlayedOrder = [objects[i][@"AlreadyPlayedIndex"] integerValue];
songListData.totRating = songListData.totLikes - songListData.totDisLikes;
songListData.createdDate = songListData.userPlaylistInfo.createdAt;
//User Specific for loading the song list.
PFQuery *queryLikeDislike = [PFQuery queryWithClassName:[SongLikeDislike parseClassName]];
[queryLikeDislike whereKey:@"SongID" equalTo:songListData.songInfo.objectId];
[queryLikeDislike whereKey:@"UserID" equalTo:[SINGLETON getUserID]];
[queryLikeDislike whereKey:@"PlaylistID" equalTo:songListData.playlistInfo.objectId];
[queryLikeDislike findObjectsInBackgroundWithBlock:^(NSArray *objectsLike, NSError *error) {
getTotalObjectsCount += 1;
if(error == nil) {
if(objectsLike.count) {
BOOL isDelete = [objectsLike.lastObject[@"DeleteRecord"] boolValue];
BOOL isLike = [objectsLike.lastObject[@"Like"] boolValue];
if(isDelete)
songListData.ratingType = RATING_GRAY;
else if(isLike)
songListData.ratingType = RATING_GREEN;
else
songListData.ratingType = RATING_RED;
}
else
songListData.ratingType = RATING_GRAY;
}
else
NSLog(@"Problem while getting the rating type");
[arrParseSongList addObject:songListData];
NSLog(@"i : %ld, objects : %ld",(long)getTotalObjectsCount, (long)objects.count);
if(getTotalObjectsCount == objects.count)
[weakSelf processAfterGettingLikesAndDislikeInfo:arrParseSongList];
}];
}
});
}
}];
}];
NSLog(@"In method -> All operation : %ld",(long)self.opearation.operations.count);
}
else
[UIAlertView showErrorWithMessage:NO_INTERNET handler:nil];
}
- (void)processAfterGettingLikesAndDislikeInfo:(NSMutableArray *)arrParseSongList {
NSPredicate *filterGrayout = [NSPredicate predicateWithFormat:@"isPlaying == YES"];
NSArray *arrGrayOut = [arrParseSongList filteredArrayUsingPredicate:filterGrayout];
NSSortDescriptor *aSortDescriptorGrayedOut = [[NSSortDescriptor alloc] initWithKey:@"alreadyPlayedOrder.intValue" ascending:YES];
NSArray *arrGrayedOutSong = [NSMutableArray arrayWithArray:[arrGrayOut sortedArrayUsingDescriptors:[NSArray arrayWithObject:aSortDescriptorGrayedOut]]];
NSPredicate *filterNonPlay = [NSPredicate predicateWithFormat:@"isPlaying == NO"];
NSArray *arrNonPlay = [arrParseSongList filteredArrayUsingPredicate:filterNonPlay];
NSSortDescriptor *aSortDescriptorRating = [[NSSortDescriptor alloc] initWithKey:@"totRating.intValue" ascending:NO];
NSSortDescriptor *aSortDescriptorCreatedDate = [[NSSortDescriptor alloc] initWithKey:@"createdDate" ascending:YES];
NSArray *arrSortOnNormalSong = [NSMutableArray arrayWithArray:[arrNonPlay sortedArrayUsingDescriptors:[NSArray arrayWithObjects:aSortDescriptorRating,aSortDescriptorCreatedDate,nil]]];
if(self.arrSongsData.count)
[self.arrSongsData removeAllObjects];
[self.arrSongsData addObjectsFromArray:arrGrayedOutSong];
[self.arrSongsData addObjectsFromArray:arrSortOnNormalSong];
[self showHideLoading:NO];
[self.tblView reloadData];
}
我在viewWillDisappear中调用。
- (void)viewWillDisappear:(BOOL)animated {
[super viewWillDisappear:animated];
if(self.queryInstance)
[self.queryInstance cancel];
}
感谢您的帮助！