ios - Swift - Collection View dequeueReusableCellWithReuseIdentifier EXC 错误访问错误

Question

我正在开发一个有 UICollectionView 的应用程序。我创建了一个包含 UIImageView 和 UILabel 的自定义 Collection View Cell。以下代码导致 cellForItemAtIndexPath 方法中的 UICollectionView.dequeueReusableCellWithReuseIdentifier 出现 EXC_BAD_ACCESS (code=1, address=0x0) 错误。
这是我的代码:

import UIKit

class CategoryCell : UICollectionViewCell {

@IBOutlet var categoryImageView : UIImageView?
@IBOutlet var categoryLabel : UILabel?

}

class CatalogCollectionViewController: UIViewController, UICollectionViewDelegate , UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {

@IBOutlet var categoriesCollectionView : UICollectionView?
var screenSize : CGRect?

override func viewDidLoad() {
    super.viewDidLoad()

    screenSize = UIScreen.mainScreen().bounds
    let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
    layout.itemSize = CGSize(width: screenSize!.width/2-30  , height: screenSize!.width/2-30 )
    layout.minimumInteritemSpacing = 10
    layout.minimumLineSpacing = 10

    self.categoriesCollectionView?.delegate = self
    self.categoriesCollectionView?.dataSource = self

    categoriesCollectionView = UICollectionView(frame: self.view.frame, collectionViewLayout: layout)
    self.categoriesCollectionView?.registerClass(CategoryCell.self, forCellWithReuseIdentifier: "CategoryCell")
    self.categoriesCollectionView?.backgroundColor=UIColor.whiteColor()
    self.view.addSubview(categoriesCollectionView!)

 }

override func viewWillAppear(animated: Bool) {


}

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

    return 1
}

func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {

    let cell = categoriesCollectionView!.dequeueReusableCellWithReuseIdentifier("CategoryCell", forIndexPath: indexPath) as! CategoryCell

    cell.layer.borderWidth = 2.0
    cell.layer.borderColor = UIColor.grayColor().CGColor

    return cell
}
func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {

    return CGSizeMake(self.view.frame.size.width/2-30, self.view.frame.size.width/2-30)
}


}

po 单元输出(调试器):

error: Execution was interrupted, reason: EXC_BAD_ACCESS (code=1,address=0x0). The process has been returned to the state before expression evaluation.

完整的堆栈跟踪:

* thread #1: tid = 0xdbea, 0x280abd6a UIKit`-[UICollectionViewData layoutAttributesForItemAtIndexPath:] + 274, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x0)
    frame #0: 0x280abd6a UIKit`-[UICollectionViewData layoutAttributesForItemAtIndexPath:] + 274
    frame #1: 0x28825da4 UIKit`-[UICollectionView _dequeueReusableViewOfKind:withIdentifier:forIndexPath:viewCategory:] + 312
    frame #2: 0x280abc38 UIKit`-[UICollectionView dequeueReusableCellWithReuseIdentifier:forIndexPath:] + 164
  * frame #3: 0x0010d428 SwiftTest`SwiftTest.CatalogCollectionViewController.collectionView (collectionView=0x1725c200, indexPath=0x16d9c560, self=0x16dbd260)(__ObjC.UICollectionView, cellForItemAtIndexPath : __ObjC.NSIndexPath) -> __ObjC.UICollectionViewCell + 296 at CatalogCollectionViewController.swift:50
    frame #4: 0x0010d850 SwiftTest`@objc SwiftTest.CatalogCollectionViewController.collectionView (SwiftTest.CatalogCollectionViewController)(__ObjC.UICollectionView, cellForItemAtIndexPath : __ObjC.NSIndexPath) -> __ObjC.UICollectionViewCell + 92 at CatalogCollectionViewController.swift:0
    frame #5: 0x2881fa74 UIKit`-[UICollectionView _createPreparedCellForItemAtIndexPath:withLayoutAttributes:applyAttributes:isFocused:] + 408
    frame #6: 0x280abb82 UIKit`-[UICollectionView _createPreparedCellForItemAtIndexPath:withLayoutAttributes:applyAttributes:] + 30
    frame #7: 0x280a9c6e UIKit`-[UICollectionView _updateVisibleCellsNow:] + 3726
    frame #8: 0x280a50aa UIKit`-[UICollectionView layoutSubviews] + 226
    frame #9: 0x28041a82 UIKit`-[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 714
    frame #10: 0x2611dad4 QuartzCore`-[CALayer layoutSublayers] + 128
    frame #11: 0x261191d0 QuartzCore`CA::Layer::layout_if_needed(CA::Transaction*) + 352
    frame #12: 0x28057f9a UIKit`-[UIView(Hierarchy) layoutBelowIfNeeded] + 962
    frame #13: 0x28103aac UIKit`-[UINavigationController _layoutViewController:] + 1168
    frame #14: 0x2810173e UIKit`-[UINavigationController _layoutTopViewController] + 250
    frame #15: 0x2811a55e UIKit`-[UINavigationController navigationTransitionView:didEndTransition:fromView:toView:] + 634
    frame #16: 0x2811a2ba UIKit`-[UINavigationTransitionView _notifyDelegateTransitionDidStopWithContext:] + 370
    frame #17: 0x2811a006 UIKit`-[UINavigationTransitionView _cleanupTransition] + 758
    frame #18: 0x280806b8 UIKit`-[UIViewAnimationState sendDelegateAnimationDidStop:finished:] + 204
    frame #19: 0x2807e9ec UIKit`+[UIViewAnimationState popAnimationState] + 324
    frame #20: 0x2810d060 UIKit`-[UINavigationTransitionView transition:fromView:toView:] + 1732
    frame #21: 0x2810c996 UIKit`-[UINavigationTransitionView transition:toView:] + 26
    frame #22: 0x28103278 UIKit`-[UINavigationController _startTransition:fromViewController:toViewController:] + 2548
    frame #23: 0x2810251a UIKit`-[UINavigationController _startDeferredTransitionIfNeeded:] + 834
    frame #24: 0x2810216c UIKit`-[UINavigationController __viewWillLayoutSubviews] + 52
    frame #25: 0x281020e6 UIKit`-[UILayoutContainerView layoutSubviews] + 214
    frame #26: 0x28041a82 UIKit`-[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 714
    frame #27: 0x2611dad4 QuartzCore`-[CALayer layoutSublayers] + 128
    frame #28: 0x261191d0 QuartzCore`CA::Layer::layout_if_needed(CA::Transaction*) + 352
    frame #29: 0x26119060 QuartzCore`CA::Layer::layout_and_display_if_needed(CA::Transaction*) + 16
    frame #30: 0x26118580 QuartzCore`CA::Context::commit_transaction(CA::Transaction*) + 368
    frame #31: 0x26118232 QuartzCore`CA::Transaction::commit() + 614
    frame #32: 0x261119ee QuartzCore`CA::Transaction::observer_callback(__CFRunLoopObserver*, unsigned long, void*) + 138
    frame #33: 0x23e70b20 CoreFoundation`__CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 20
    frame #34: 0x23e6ee16 CoreFoundation`__CFRunLoopDoObservers + 282
    frame #35: 0x23e6f254 CoreFoundation`__CFRunLoopRun + 972
    frame #36: 0x23dc1bb8 CoreFoundation`CFRunLoopRunSpecific + 516
    frame #37: 0x23dc19ac CoreFoundation`CFRunLoopRunInMode + 108
    frame #38: 0x2503baf8 GraphicsServices`GSEventRunModal + 160
    frame #39: 0x280adfb4 UIKit`UIApplicationMain + 144
    frame #40: 0x00108050 SwiftTest`main + 164 at AppDelegate.swift:12

Answer 1

这样做比较好，

if let cell = collectionView.dequeueReusableCellWithReuseIdentifier("CategoryCell", forIndexPath: indexPath) as? CategoryCell { .....(rest of your method code) }

通过这种方式，您可以确保在尝试在其上运行代码之前确实拥有一个可重用的单元格。此外，最好使用方法 collectionView 而不是任何 socket 。