我有一个奇怪的情况与我的UItableView。ios8 UITableView滚动时滚动跳回
我从互联网加载图像,并以异步方式将它们呈现在uitableviewcell中。当我向下滚动(即第1行到第6行)时,滚动顺畅地向下滚动,就像我期望的那样。
但是,然后我向上滚动(例如,第6行到第1行),滚动跳回。例如,如果我从第6行滚动到第5行,它将跳回到第6行。第二次,我尝试向上滚动,让我上行到第4行,但它然后滚动我回到第5或第6行,但通常只是5.
我不明白的是为什么这只发生在一个方向。
这似乎是影响IOS 8而不是IOS 7
因此,它是如何iOS8上和7处理的UITableView的实现差异。
我该如何解决这个问题?
下面是一些代码给你一些背景
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
CVFullImageTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"cell" forIndexPath:indexPath];
CVComicRecord *comicRecord = self.comicRecords[indexPath.row];
[cell.loaderGear stopAnimating];
[cell.text setText:comicRecord.title];
NSString *UUID = comicRecord.fullImagePageURL.absoluteString;
[cell setUUID:UUID];
//Check if image is in the cache
UIImage *fullImage = [self.contentViewCache objectForKey:UUID];
[cell setComicFullImage:fullImage];
if (fullImage) {
return cell;
}
[cell.loaderGear startAnimating];
[self requestImageForIndexPath:indexPath];
return cell;
}
- (void)requestImageForIndexPath:(NSIndexPath *)indexPath {
CVComicRecord *comicRecord = self.comicRecords[indexPath.row];
NSString *UUID = comicRecord.fullImagePageURL.absoluteString;
if ([self.contentViewCache objectForKey:UUID]) {
//if it is already cached, I do not need to make a request.
return;
}
id fd = CVPendingOperations.sharedInstance.fullDownloadersInProgress[UUID];
if (fd) {
//if it is in the queue you do no need to make a request
return;
}
comicRecord.failedFull = NO;
CVFullImageDownloader *downloader = [[CVFullImageDownloader alloc] initWithComicRecord:comicRecord withUUID:UUID];
[CVPendingOperations.sharedInstance.fullDownloaderOperationQueue addOperation:downloader];
//when operation completes it will post a notification that will trigger an observer to call fullImageDidFinishDownloading
}
- (void)fullImageDidFinishDownloading:(NSNotification *)notification {
CVComicRecord *comicRecord = notification.userInfo[@"comicRecord"];
NSString *UUID = notification.userInfo[@"UUID"];
UIImage *fullImage = notification.userInfo[@"fullImage"];
comicRecord.failedFull = NO;
[self.contentViewCache setObject:fullImage forKey:UUID];
dispatch_async(dispatch_get_main_queue(), ^{
for (NSIndexPath *indexPath in [self.tableView indexPathsForVisibleRows]) {
CVFullImageTableViewCell *cell = (id)[self.tableView cellForRowAtIndexPath:indexPath];
if (cell) {
if ([cell.UUID isEqualToString:UUID]) {
[cell.loaderGear stopAnimating];
[cell setComicFullImage:fullImage];
[cell layoutIfNeeded];
}
}
}
});
}
#pragma mark - Scroll
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
static int oldOffset = 0;
int newOffset = scrollView.contentOffset.y;
int dy = newOffset- oldOffset;
if (dy > 0) {
[self hideNavigationbar:YES animationDuration:0.5];
} else if (dy < 0) {
[self hideNavigationbar:NO animationDuration:0.5];
}
oldOffset = newOffset;
}
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate {
if (decelerate == NO) {
[self prioritizeVisisbleCells];
//currentPage is a property that stores that last row that the user has seen
[self setCurrentPage:[self currentlyViewedComicIndexPath].row];
}
}
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
[self prioritizeVisisbleCells];
//currentPage is a property that stores that last row that the user has seen
[self setCurrentPage:[self currentlyViewedComicIndexPath].row];
}
- (void)prioritizeVisisbleCells {
NSArray *ips = [self.tableView indexPathsForVisibleRows];
NSArray *activeIndexPaths = [CVPendingOperations.sharedInstance.fullDownloadersInProgress allKeys];
//add visible cells to queue first
NSSet *visible = [NSSet setWithArray:ips];
NSMutableSet *invisible = [NSMutableSet setWithArray:activeIndexPaths];
[invisible minusSet:visible];
for (NSIndexPath *ip in invisible) {
NSOperation *op = CVPendingOperations.sharedInstance.fullDownloadersInProgress[ip];
[op setQueuePriority:NSOperationQueuePriorityNormal];
}
for (NSIndexPath *ip in visible) {
NSOperation *op = CVPendingOperations.sharedInstance.fullDownloadersInProgress[ip];
[op setQueuePriority:NSOperationQueuePriorityHigh];
}
}
你配置单元格的代码是什么样的? – 2014-09-29 18:14:50
我发现这个bug影响ios 8而不是ios 7 – DerrickHo328 2014-09-29 18:25:35
@ Calimari328请回答你被问到的问题。这里没有iOS 8的bug。这是_you_做错了。如果你需要帮助,你必须显示你在做什么。 – matt 2014-09-29 18:33:40