Question

我有UICollectionView和两个UIButton：WeekButton和MonthButton。当我触摸WeekButton或MonthButton时，我希望UICollectionView显示我的数据源的最后一个元素。 WeekButton和MonthButton函数之间的区别在于UICollectionView的单元格大小。当我触摸两个按钮中的任何一个时，我调用scrollToItem。当我触摸MonthButton时它工作得很好，但是当我触摸WeekButton时却没有。如果我触摸WeekButton两次就行了。我想知道为什么当我第一次触摸WeekButton时它不起作用

@IBAction func touchWeekButton(_ sender: UIButton) {
    dateProcess.isWeek=true
    dateProcess.item=historyItem
    dateCollectionView.reloadData()
    print("touchWeekButton")
    scrollToBottom()
}
@IBAction func touchMonthButton(_ sender: UIButton) {
    dateProcess.isWeek=false
    dateProcess.item=historyItem
    dateCollectionView.reloadData()
    scrollToBottom()
}

func scrollToBottom(){       
    let maxIndexPath=IndexPath(row: dateProcess.colorArray.count-1, section:0 )
    self.dateCollectionView.scrollToItem(at: maxIndexPath, at: UICollectionViewScrollPosition.bottom, animated: false)
}

扩展HistoryViewController：UICollectionViewDelegateFlowLayout {

func collectionView(_ collectionView: UICollectionView,
                    layout collectionViewLayout: UICollectionViewLayout,
                    sizeForItemAt indexPath: IndexPath) -> CGSize {
    if dateProcess.isWeek==true{
        let colViewHeight=collectionView.bounds.height
        let colViewWidth=collectionView.bounds.width
        let cellWidth=colViewWidth/7-1
        let cellHeight=colViewHeight/4
        return CGSize(width: cellWidth, height: cellHeight)
    }else{
        let colViewHeight=collectionView.bounds.height
        let colViewWidth=collectionView.bounds.width
        let cellWidth=colViewWidth/31
        let cellHeight=colViewHeight/16
        return CGSize(width: cellWidth, height: cellHeight)
    }

}

}

Answer 1

可能你需要等到你的collectionView重新加载，然后才能滚动到任何项目。你可以这样做：

@IBAction func touchWeekButton(_ sender: UIButton) {
    dateProcess.isWeek=true
    dateProcess.item=historyItem
    dateCollectionView.reloadData()
    print("touchWeekButton")
    DispatchQueue.main.async {

        scrollToBottom()            
    }
}
@IBAction func touchMonthButton(_ sender: UIButton) {
    dateProcess.isWeek=false
    dateProcess.item=historyItem
    dateCollectionView.reloadData()
    DispatchQueue.main.async {

        scrollToBottom()            
    }
}

scrollToItem不起作用

1 个答案: