Question

我有UICollectionView个自定义单元格，我想在其中显示一些倒计时。我遇到的问题是，当我有一个带倒计时的单元格并将其向下滚动时，其中不应该有倒计时的单元格也会显示倒计时。

我知道这与细胞的重复使用有关，但不确定我该怎么办。这是我的代码：

cellForItemAtIndexPath：

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    MainCell *cell = (MainCell *)[collectionView dequeueReusableCellWithReuseIdentifier:@"MainCell" forIndexPath:indexPath];

if(displayCountDown.boolValue){
            NSDate *endTime = [offer objectForKey:@"expiresDate"];
            [cell startTimer:endTime];
            cell.imgTimeLeftClock.hidden = NO;
}else{
            cell.lblTimeLeft.text = @"No time limit";
            cell.imgTimeLeftClock.hidden = YES;

}

return cell;

}

在MainCell.m内部：

- (void) startTimer :(NSDate *) endTime
{

        [self.timer invalidate];        

        self.startTime = [NSDate date];        
        self.endTime = endTime;

        double startTimeDouble = [self.startTime timeIntervalSince1970];
        int currentTimeRound = (int)startTimeDouble;

        double endTimeDouble = [self.endTime timeIntervalSince1970];
        int endTimeRound = (int)endTimeDouble;

        self.secondsLeft = endTimeRound - currentTimeRound;        

        // create a new timer
        self.timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(calculateTimer) userInfo:nil repeats:YES];

        [[NSRunLoop currentRunLoop] addTimer:self.timer forMode:NSRunLoopCommonModes];

        [self.timer fire];


}

- (void)calculateTimer
{

    self.secondsLeft--;

    if(self.secondsLeft > 0){
        int days = self.secondsLeft / 86400;
        int hours = (self.secondsLeft / 3600) %  24;
        int minutes = (self.secondsLeft % 3600) / 60;
        int seconds = (self.secondsLeft %3600) % 60;

        self.lblTimeLeft.text = [NSString stringWithFormat:@"%02d:%02d:%02d:%02d", days, hours, minutes, seconds];
    }else{
        self.lblTimeLeft.text = @"Time's up";
    }
}

我能做些什么才能让倒计时只显示在正确的细胞上？

Answer 1

你应该使用在数组中存储具有计时器的单元格（即timerArray）并使用此数组向该单元格添加计时器，如下所示，

-(NSInteger)collectionView:(UICollectionView *)collectionView
numberOfItemsInSection:(NSInteger)section
{
    return collectionViewArray.count;
}


- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
MainCell *cell = (MainCell *)[collectionView dequeueReusableCellWithReuseIdentifier:@"MainCell" forIndexPath:indexPath];

   if(displayCountDown.boolValue){
   //In place of this bool check you could simply check if that object(collectionViewArray) is in your timerArray.

   //Your timerArray will contain obj which are having timer in it and collectionViewArray is your array having all objects(with/without timer and is actual array that you use for count)      

   //Then if-else condition will go similarly.

        NSDate *endTime = [offer objectForKey:@"expiresDate"];
        [cell startTimer:endTime];
        cell.imgTimeLeftClock.hidden = NO;
   }else{
        cell.lblTimeLeft.text = @"No time limit";
        cell.imgTimeLeftClock.hidden = YES;

  }
 return cell;
}

希望这能帮到你！

Answer 2

您在cellForItem中的逻辑基于displayCountDown.boolValue，但它也应该基于单元格的indexPath。因此，每次调用cellForItem时，您都知道哪个单元格应该显示标签以及何时应该隐藏它。您可以根据索引路径打开或关闭它。否则就像你说集合视图将重用它。

重用时，UICollectionViewCell子类内的倒计时逻辑

2 个答案: