Question

我试图每5秒自动滚动收集视图单元格，所以我创建了一个计时器并尝试了以下代码：

-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    BannerCell *cell = [self.bannerCollectionView dequeueReusableCellWithReuseIdentifier:@"bannerCell" forIndexPath:indexPath];
    //cell.isRoundImg = YES;
    [cell fillCellWithBanner:self.banners[indexPath.row]];
    NSInteger rowIndex = indexPath.row;
    NSInteger numberOfRecords = self.banners.count -1;
    if(rowIndex < numberOfRecords){
        rowIndex = (rowIndex + 1);
    }else {
        rowIndex = 0;
    }
    self.scrollingTimer = [NSTimer scheduledTimerWithTimeInterval:5.0 target:self selector:@selector(startTimer:) userInfo:@{@"index" : [NSString stringWithFormat:@"%ld", (long)rowIndex]} repeats:YES];

    return cell;
}

-(void)startTimer:(NSTimer *)timer{
    NSString *indexString = timer.userInfo[@"index"];
    NSInteger indexRow = [indexString integerValue];
    NSLog(@"%ld", (long)indexRow);
   // [UIView animateWithDuration:1 delay:0 options:UIViewAnimationOptionCurveEaseOut animations:^{
        [self.bannerCollectionView scrollToItemAtIndexPath:[NSIndexPath indexPathForRow:indexRow inSection:0] atScrollPosition:UICollectionViewScrollPositionCenteredHorizontally animated:NO];
  //  } completion:nil];
}

当我启动该应用程序时，我可以正常工作，但是大约30秒后，一切都出了问题，单元格的滚动速度非常快，计时器功能在1秒钟内被调用了大约10次以上。有人知道问题出在哪里吗？谢谢

Answer 1

从cellForItemAtIndexPath方法中删除此行，并在viewDidLoad方法中使用

self.scrollingTimer = [NSTimer scheduledTimerWithTimeInterval:5.0 target:self selector:@selector(startTimer:) userInfo:@{@"index" : [NSString stringWithFormat:@"%ld", (long)rowIndex]} repeats:YES];

timers函数在1秒内被调用了约10次以上

cellForItemAtIndexPath方法被多次调用。并且每次都会创建一个新的计时器。如果创建了10个计时器，则这些单元的动画速度将提高10倍。

OR

在scrollingTimer中检查cellForItemAtIndexPath是否已经启动

if (!scrollingTimer.isValid) {
    self.scrollingTimer = [NSTimer scheduledTimerWithTimeInterval:5.0 target:self selector:@selector(startTimer:) userInfo:@{@"index" : [NSString stringWithFormat:@"%ld", (long)rowIndex]} repeats:YES];
}

使用计时器自动滚动Collectionview单元格

1 个答案: