使用多个UICollectionView，获取错误，“...必须使用非零布局初始化”。 [英] With Multiple UICollectionView's, getting error, "... must be initialized with non-nil layout"

问题描述

我最近开始使用Swift，我试图从页面上的一个UICollectionView（有效）到最多两个。我收到错误

I have recently started working with Swift, and I am trying to go from one UICollectionView on the page (which worked) up to two of them. I am getting the error

因未捕获的异常而终止应用程序' NSInvalidArgumentException'，原因：'UICollectionView必须初始化为非零布局参数'。

到目前为止我在Stack Overflow上找到的内容已经整合到我的代码中，但我仍然收到错误。我在我的智慧结束，请帮助！

What I've found thus far on Stack Overflow has been incorporated into my code, but I am still getting the error. I am at my wit's end, please help!

我去过的地方：

• 我开始使用这篇文章关于设置UICollectionView，一切正常。


• 现在在同一个屏幕上设置第二个UICollectionView，我按照这篇文章。


• 一切似乎都没问题，我得到Build Succeeded，紧随其后应用程序开始运行时，崩溃迅速发生。错误消息显示：

• I Started with this article on setting up the UICollectionView, and everything worked just fine.
• Now to set up a second UICollectionView on the same screen, I followed the instructions in this article.
• Everything seems okay, I get "Build Succeeded", followed promptly by a crash as the app starts to run. Error message says:

***由于未捕获的异常'NSInvalidArgumentException'而终止应用程序，原因：'UICollectionView必须使用非零布局参数初始化'

• 在StackOverflow中查找该错误，我找到< a href =https://stackoverflow.com/questions/40417252/uicollectionviewcontroller-error-in-swift-3-0-must-be-initialized-with-a-non-ni>这篇文章（它处理的是单个UICollectionView，而不是我所拥有的两个。


• 我已经从那篇文章中实现了所有内容，但我仍然收到错误，现在我出于想法。我的代码如下，任何帮助都将非常感谢！

• Looking for that error in StackOverflow, I find this article (which deals with a single UICollectionView, rather than the two that I have).
• I've implemented everything I can from that article, but I'm still getting the error, and am now out of ideas. My code is below, any help would be most greatly appreciated!

ViewController.swift ：

import UIKit
class ViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate {

var collectionViewLeft = UICollectionView()                         // changed "let" to "var" so I can assign things to it in viewDidLoad()
var collectionViewRight = UICollectionView()
let collectionViewLeftIdentifier = "CollectionViewLeftCell"
let collectionViewRightIdentifier = "CollectionViewRightCell"

override func viewDidLoad() {

    super.viewDidLoad()

    let layoutLeft = UICollectionViewFlowLayout()                   // this is what **I would think** would be my non-nil layout
    layoutLeft.itemSize = CGSize(width: 100, height: 100)

    let layoutRight = UICollectionViewFlowLayout()
    layoutRight.itemSize = CGSize(width: 100, height: 100)

    collectionViewLeft = UICollectionView(frame: self.view.frame, collectionViewLayout: layoutLeft)
    collectionViewRight = UICollectionView(frame: self.view.frame, collectionViewLayout: layoutRight)

    collectionViewLeft.delegate = self
    collectionViewRight.delegate = self

    collectionViewLeft.dataSource = self
    collectionViewRight.dataSource = self

    self.view.addSubview(collectionViewLeft)
    self.view.addSubview(collectionViewRight)

    collectionViewLeft.register(UICollectionViewCell.self, forCellWithReuseIdentifier: collectionViewLeftIdentifier)
    collectionViewRight.register(UICollectionViewCell.self, forCellWithReuseIdentifier: collectionViewRightIdentifier)

}


let reuseIdentifierLeft = "cellLeft" // also enter this string as the cell identifier in the storyboard
let reuseIdentifierRight = "cellRight"

var itemsRight = ["1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "20", "21", "22", "23", "24", "25", "26", "27", "28", "29", "30", "31", "32", "33", "34", "35", "36", "37", "38", "39", "40", "41", "42", "43", "44", "45", "46", "47", "48"]
var itemsLeft = ["10", "20", "30", "40", "50", "60"]


// MARK: - UICollectionViewDataSource protocol

// tell the collection view how many cells to make
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {

    if collectionView == self.collectionViewLeft {
            return self.itemsLeft.count

    } else if collectionView == self.collectionViewRight {
            return self.itemsRight.count
    } else {
        print("This is very bad")
        assert(false, "Passed collectionView is neither collectionViewLeft nor collectionViewRight -- ruh roh!")
        return 0
    }
}

// make a cell for each cell index path
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

    if collectionView == self.collectionViewLeft {
        // get a reference to our storyboard cell
        let cellLeft = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifierLeft, for: indexPath as IndexPath) as! MyCollectionViewCell

        // Use the outlet in our custom class to get a reference to the UILabel in the cell
        cellLeft.myLeftLabel.text = self.itemsLeft[indexPath.item]
        cellLeft.backgroundColor = UIColor.red // make cell more visible in our example project

        return cellLeft
    } else if collectionView == self.collectionViewRight {
        let cellRight = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifierRight, for: indexPath as IndexPath) as! MyRightCollectionViewCell

        // Use the outlet in our custom class to get a reference to the UILabel in the cell
        cellRight.myRightLabel.text = self.itemsRight[indexPath.item]
        cellRight.backgroundColor = UIColor.green // make cell more visible in our example project

        return cellRight
    } else {
        print("This is very bad")
        assert(false, "Passed collectionView is neither collectionViewLeft nor collectionViewRight -- ruh roh!")

        // won't actually execute the following, but to keep the compiler happy...
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifierLeft, for: indexPath as IndexPath) as! MyCollectionViewCell
        return cell
    }
}

// MARK: - UICollectionViewDelegate protocol

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {

    // handle tap events

    if collectionView == self.collectionViewLeft {
        print("You tapped cell #\(indexPath.item) on the LEFT!")
    } else if collectionView == self.collectionViewRight {
        print("You tapped cell #\(indexPath.item) on the RIGHT!")
    } else {
        print("This is very bad")
        assert(false, "Passed collectionView is neither collectionViewLeft nor collectionViewRight -- ruh roh!")
    }
}

}

MyCollectionViewCell.swift

import UIKit

class MyCollectionViewCell: UICollectionViewCell {

    @IBOutlet weak var myLeftLabel: UILabel!

}

class MyRightCollectionViewCell: UICollectionViewCell {

    @IBOutlet weak var myRightLabel: UILabel!

}

推荐答案

我的猜测，你声明 UICollectionViewController 的空默认值 init 构造函数作为变量：

My guess, you declare UICollectionViewController's with empty default init constructor as variables:

var collectionViewLeft = UICollectionView()
var collectionViewRight = UICollectionView()

尝试在没有构造函数的情况下替换变量声明：

Try to replace your variable declarations without constructors:

以下编辑的代码：正如@ Paulw11正确指出的那样他的回答如下，最好使用一个隐式解包的可选项！而不是？

Edited code below: As @Paulw11 correctly noted in his answer below, it's better to use an implicitly unwrapped optional ! rather than ?

var collectionViewLeft: UICollectionView!
var collectionViewRight: UICollectionView!

无论如何，你要在 viewDidLoad 具有指定初始化程序的功能 UICollectionView 。

Anyway, you are instantiate them in your viewDidLoad function with designated initialisers for UICollectionView.

只需注意，最好先注册自定义类/ xib UICollectionView 被添加为子视图。它现在并不重要，但在重构后可能会出现问题。等，因为您的代码可以调用 UICollectionView 委托或 dataSource 在为单元格编写注册的自定义类之前的函数。只需调用 .register（）上面的 self.view.addSubview（）：

And just a note, it's better to register custom class / xibs before UICollectionView is added as a subview. It's not critical right now, but may be a problem after refactoring & etc., because you code can call UICollectionView delegate or dataSource functions before you code registered custom classes for cells. Just move your code with calls to .register() above self.view.addSubview():

collectionViewLeft.register(UICollectionViewCell.self, forCellWithReuseIdentifier: collectionViewLeftIdentifier)
collectionViewRight.register(UICollectionViewCell.self, forCellWithReuseIdentifier: collectionViewRightIdentifier)

这篇关于使用多个UICollectionView，获取错误，“...必须使用非零布局初始化”。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！