使 UICollectionView 连续滚动 [英] Making a UICollectionView continuously scroll

问题描述

我有一个游戏，我需要让一块字母板不断滚动，并循环遍历一组数据(A、D、X、S、R、P、F、G、H、Y、W，M)(像这样:

希望对你有帮助:)

I have a game where I need to have a board of letters continuously scrolling, and looping through a set of data (A, D, X, S, R, P, F, G, H, Y, W, M) (Like this: https://www.youtube.com/watch?v=z3rO8TbkS-U&feature=youtu.be). When a user taps on a letter, the letter needs to be removed from the board. I can't have the board stop scrolling, it needs to continuously scroll.

I'm not exactly sure how to do this. I've been trying to do this with a UICollectionView, but I'm not exactly sure how to do this.

Any help would be greatly appreciated! Thanks :)

解决方案

Infinite scrolling in collection view can be achieved with a very easy technique.

Note: This technique is reportedly not working from iOS 12. For better results I am adding a new method after explaining this one.

1) Return a huge number in numberOfItemsInSection delegate method of collection view.

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

     return Int(INT_MAX)
}

2) Modulo the number of items in collection view with the count of your array or dictionary whatever you are using to get repeating data.

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell{

     let cell = collectionView.dequeueReusableCell(withReuseIdentifier: 
                cellIdentifier, for: indexPath)
     let displayText = indexPath.row % 10
     cell.displayLabel.text = String(displayText)
     return cell

}

Here i have no data thus i am using indexPath.row to display the row number in my label.

Suppose i have 10 data to display and currently i have huge number of items so i modulo 10 with number the current item. you can modulo the row with count of your array or dictionary as below:

let displayText = aryData.count % 10

Now explaining another technique which will work in any iOS and will give better output:

1) multiply the number of items in array by 2 and then we need to play with the content offset of collectionview. I am posting the code below on how to handle this technique.

func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return aryData.count * 2
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = colView.dequeueReusableCell(withReuseIdentifier: cellIdentifier, for: indexPath) as! colViewCell

        var index = indexPath.item
        if index > aryData.count - 1 {
            index -= aryData.count
        }
        cell.displayLabel.text = aryData[index % aryData.count]
        return cell
    }

    func collectionView(_ collectionView: UICollectionView, willDisplay cell: UICollectionViewCell, forItemAt indexPath: IndexPath) {

        // if collection view scrolls vertically, use offset.y else comment below code
        var offset = collectionView.contentOffset
        let height = collectionView.contentSize.height
        if offset.y < height/4 {
            offset.y += height/2
            collectionView.setContentOffset(offset, animated: false)
        } else if offset.y > height/4 * 3 {
            offset.y -= height/2
            collectionView.setContentOffset(offset, animated: false)
        }

        // if collection view scrolls horizontally, use offset.x else comment below line of code
        // In my case the collectionview scrolls vertically this I am commenting below line of code
        //        let width = collectionView.contentSize.width
        //        if offset.x < width/4 {
        //            offset.x += width/2
        //            collectionView.setContentOffset(offset, animated: false)
        //        } else if offset.x > width/4 * 3 {
        //            offset.x -= width/2
        //            collectionView.setContentOffset(offset, animated: false)
        //        }
    }

Below is the output of this code.

Hope this will help you :)

这篇关于使 UICollectionView 连续滚动的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！