我正在尝试创建一个简单的应用程序,其中可以为UICollectionView输入多个列和多个行。然后,集合视图计算适合它的可能方块的大小并绘制它们。 我想允许最多32个宽度和64个高度。滚动被禁用,因为整个网格应该立即显示。
例如,4x8看起来像这样
和8x4将如下所示
因此可以看出工作正常。问题伴随着更多的列和/或行。最多30x8一切都很好但从31开始只绘制了8行中的6个。
所以我不明白为什么。以下是我用来计算所有内容的代码:
部分数和行数:
func numberOfSections(in collectionView: UICollectionView) -> Int
{
let num = Int(heightInput.text!)
if(num != nil)
{
if(num! > 64)
{
return 64
}
return num!
}
return 8
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int
{
let num = Int(widthInput.text!)
if(num != nil)
{
if(num! > 32)
{
return 32
}
return num!
}
return 4
}
indexPath项目的单元格
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell
{
let size = calculateCellSize()
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath)
var origin = cell.frame.origin
origin.x = 1+CGFloat(indexPath.row) + size.width*CGFloat(indexPath.row)
origin.y = 1+CGFloat(indexPath.section) + size.height*CGFloat(indexPath.section)
cell.frame = CGRect(origin: origin, size: size)
NSLog("Cell X:%@, Cell Y:%@",origin.x.description,origin.y.description)
return cell
}
计算尺寸方法
func calculateCellSize() -> CGSize
{
//First check if we have valid values
let col = Int(widthInput.text!)
let row = Int(heightInput.text!)
if(col == nil || row == nil)
{
return CGSize(width: 48.0, height: 48.0)
}
//If there are more or equal amount of columns than rows
let columns = CGFloat(col!)
let rows = CGFloat(row!)
if(columns >= rows)
{
//Take the grid width
let gridWidth = drawCollection.bounds.size.width
//Calculate the width of the "pixels" that fit the width of the grid
var pixelWidth = gridWidth/columns
//Remember to substract the inset from the width
let drawLayout = drawCollection.collectionViewLayout as? UICollectionViewFlowLayout
pixelWidth -= (drawLayout?.sectionInset.left)! + 1/columns
return CGSize(width: pixelWidth, height: pixelWidth)
}
else
{
//Rows are more than columns
//Take the grid height as reference here
let gridHeight = drawCollection.bounds.size.height
//Calculate the height of the "pixels" that fit the height of the grid
var pixelHeight = gridHeight/rows
//Remember to substract the inset from the height
let drawLayout = drawCollection.collectionViewLayout as? UICollectionViewFlowLayout
pixelHeight -= (drawLayout?.sectionInset.top)! + 1/rows
return CGSize(width: pixelHeight, height: pixelHeight)
}
return CGSize(width: 48.0, height: 48.0)
}
出于调试原因,我将一个计数器放入cellforItemAtIndexPath方法中,实际上我可以看到最后两行没有被调用。计数器结束于185但理论上应该被称为248次,实际上差异将显示为2 * 32 - 1(对于不均匀的31)所以最后丢失的行....
有几件事情让我想到了原因是什么,但似乎没有:
总结:
是否可以显示网格中的所有元素(最大32x64),如果是,那么我的实现有什么问题?
谢谢大家的时间和答案!
答案 0 :(得分:1)
你正在做很多计算你不需要做的事情。此外,设置单元格的.frame
是一个非常糟糕的主意。集合视图的一个重点是避免必须设置框架。
看看这个:
class GridCollectionViewController: UIViewController, UICollectionViewDataSource {
@IBOutlet weak var theCV: UICollectionView!
var numCols = 0
var numRows = 0
func updateCV() -> Void {
// subtract the number of colums (for the 1-pt spacing between cells), and divide by number of columns
let w = (theCV.frame.size.width - CGFloat((numCols - 1))) / CGFloat(numCols)
// subtract the number of rows (for the 1-pt spacing between rows), and divide by number of rows
let h = (theCV.frame.size.height - CGFloat((numRows - 1))) / CGFloat(numRows)
// get the smaller of the two values
let wh = min(w, h)
// set the cell size
if let layout = theCV.collectionViewLayout as? UICollectionViewFlowLayout {
layout.itemSize = CGSize(width: wh, height: wh)
}
// reload the collection view
theCV.reloadData()
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
// start with a 31x20 grid, just to see it
numCols = 31
numRows = 20
updateCV()
}
func numberOfSections(in collectionView: UICollectionView) -> Int {
return numRows
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return numCols
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = theCV.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath)
return cell
}
@IBAction func btnTap(_ sender: Any) {
// example of changing the number of rows/columns based on user action
numCols = 32
numRows = 64
updateCV()
}
}
答案 1 :(得分:0)
您需要开发自己的UICollectionViewLayout。通过这种方法,您可以实现人类可以想象的任何结果。
import UIKit
class CollectionLayout: UICollectionViewFlowLayout {
private var width: Int = 1
private var height: Int = 1
func set(width: Int, height: Int) {
guard width > 0, height > 0 else { return }
self.height = height
self.width = width
calculateItemSize()
}
private func calculateItemSize() {
guard let collectionView = collectionView else { return }
let size = collectionView.frame.size
var itemWidth = size.width / CGFloat(width)
// spacing is needed only if there're more than 2 items in a row
if width > 1 {
itemWidth -= minimumInteritemSpacing
}
var itemHeight = size.height / CGFloat(height)
if height > 1 {
itemHeight -= minimumLineSpacing
}
let edgeLength = min(itemWidth, itemHeight)
itemSize = CGSize(width: edgeLength, height: edgeLength)
}
// calculate origin for every item
override func layoutAttributesForItem(at indexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
let attributes = super.layoutAttributesForItem(at: indexPath)
// calculate item position in the grid
let col = CGFloat(indexPath.row % width)
let row = CGFloat(Int(indexPath.row / width))
// don't forget to take into account 'minimumInteritemSpacing' and 'minimumLineSpacing'
let x = col * itemSize.width + col * minimumInteritemSpacing
let y = row * itemSize.height + row * minimumLineSpacing
// set new origin
attributes?.frame.origin = CGPoint(x: x, y: y)
return attributes
}
// accumulate all attributes
override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
guard let attributes = super.layoutAttributesForElements(in: rect) else { return nil }
var newAttributes = [UICollectionViewLayoutAttributes]()
for attribute in attributes {
if let newAttribute = layoutAttributesForItem(at: attribute.indexPath) {
newAttributes.append(newAttribute)
}
}
return newAttributes
}
}
将我们的布局设置为UICollectionView
每次用户输入宽度和高度时更新集合视图:
@IBAction func onSetTapped(_ sender: Any) {
width = Int(widthTextField.text!)
height = Int(heightTextField.text!)
if let width = width, let height = height,
let layout = collectionView.collectionViewLayout as? CollectionLayout {
layout.set(width: width, height: height)
collectionView.reloadData()
}
}