swift:滚动collectionView

Question

我有collectionView，我想滚动到下一部分按钮点击。怎么做？

func numberOfSections(in collectionView: UICollectionView) -> Int {
        return 4  
    }

func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 3
    }

@IBAction func nextAction(_ sender: Any) {
        //scroll to next
    }

更新

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {

        cellOffset = 10

        cellWidth = (collectionView.bounds.width / 3)  - (cellOffset * 4)
        cellHeight = (cellWidth / 2 * 3) + (cellWidth / 2 * 0.65)

        return CGSize(width: cellWidth, height: cellHeight)
    }

Answer 1

这可以通过一些简单的步骤来完成：

• 查找当前可见的第一个区段的节号。
• 如果区段号不是最后一节，则向其中添加1。
• 滚动到具有新节号的区段。 设currentlyVisibleSection = collectionView.indexPathsForVisibleItems.map {$0.节}.min()！如果currentlyVisibleSection <3{让scrollToSection = currentlyVisibleSection +1 collectionView.scrollToItem(at: IndexPath(项目: 0，节: scrollToSection)，at：.top，动画:真)}}

Answer 2

假设您有一个跟踪当前滚动部分的变量。

@IBAction func nextAction(_ sender: Any) {

    let attr = collectionView.layoutAttributesForItem(at: IndexPath.init(row: 0, section: currentSection))
    collectionView.setContentOffset(attr!.frame.origin, animated: true)
    currentSection += 1;
    if currentSection >= maxSectionCount {
        currentSection = maxSectionCount - 1
    }
}

Answer 3

func goToNextSection() {
    guard let nextIndex = getNextSectionIndex() else {
        return
    }
    goToItemAt(nextIndex)
}

func getNextSectionIndex() -> IndexPath? {
    guard let firstVisibleCell = mycollection.visibleCells.first, // maybe last in your scenario
        let indexOfFirstCell = mycollection.indexPath(for: firstVisibleCell) else {
        return nil
    }
    let nextIndex = IndexPath(item: 0, section: indexOfFirstCell.section + 1)
    let yesIhaveCellsHere = true // you need to check if your DS has 'cells' for this, otherwise it will crash at scroll to item
    guard yesIhaveCellsHere else {
        return nil
    }
    return nextIndex
}

func goToItemAt(_ index: IndexPath) {
    mycollection.scrollToItem(at: index,
                              at: UICollectionViewScrollPosition.left, // adjust for your scenario
                              animated: true)
}