iOS SIGSEGV SEGV_ACCERR 在layoutSubviews 中崩溃

Question

我的应用程序有时会在layoutSubview方法中崩溃。当应用程序计算 UITableViewCell 的高度时会发生这种情况。应用程序有时会崩溃，但并非总是如此。这里的函数代码:

+ (CGFloat)heightForEditorialCommentData:(EditorialCommentVMData *)editorialData
{
    EditorialCommentCell * cell = [EditorialCommentCell instanceCell];
    [cell applyViewModelData:editorialData];
    [cell layoutSubviews];
    return cell.commentTextLabel.frameBottom + kTextInsets.bottom;
}

+ (EditorialCommentCell *)instanceCell {
    static EditorialCommentCell *instance = nil;

    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        NSArray *views = [[NSBundle mainBundle] loadNibNamed: @"EditorialCommentCell" owner:0 options:0];
        instance = views[0];
        instance.frame = CGRectMake(instance.contentView.frame.origin.x,
                                        instance.contentView.frame.origin.y,
                                        [[UIScreen mainScreen] bounds].size.width,
                                        instance.contentView.frame.size.height);
    });

    return instance;
}

这是堆栈跟踪:

Thread : Crashed: com.apple.root.default-qos
 0  UIKit                          0x2ff92b3a -[_UIViewAdditiveAnimationAction runActionForKey:object:arguments:] + 569
 1  UIKit                          0x2ff92cf5 __67-[_UIViewAdditiveAnimationAction runActionForKey:object:arguments:]_block_invoke + 408
 2  QuartzCore                     0x2f71e4c5 CA::Layer::end_change(CA::Transaction*, unsigned int, objc_object*) + 96
 3  QuartzCore                     0x2f71f06b CA::Layer::set_bounds(CA::Rect const&, bool) + 530
 4  QuartzCore                     0x2f71ed87 -[CALayer setBounds:] + 110
 5  UIKit                          0x3017f84f -[_UILabelLayer setBounds:] + 58
 6  QuartzCore                     0x2f71fe01 -[CALayer setFrame:] + 600
 7  UIKit                          0x3017f7eb -[_UILabelLayer setFrame:] + 58
 8  UIKit                          0x2fcfc4d7 -[UIView(Geometry) setFrame:] + 254
 9  UIKit                          0x2fd09f53 -[UILabel setFrame:] + 138
 CRASH->10 MYAPP                     0x000fb611 -[UIView(Frame) setFrameWidth:] (UIView+Frame.m:103)
 11 MYAPP                     0x00130c75 -[EditorialCommentCell layoutSubviews] (EditorialCommentCell.m:139)
 12 MYAPP                     0x001324ed +[EditorialCommentCell heightForEditorialCommentData:] (EditorialCommentCell.m:351)
 13 MYAPP                     0x00115733 -[EditorialCommentsViewModel applyDataFromItem:toVMItem:] (EditorialCommentsViewModel.m:298)
 14 MYAPP                     0x00114e73 -[EditorialCommentsViewModel vmDataFromItem:] (EditorialCommentsViewModel.m:222)
 15 MYAPP                     0x000fac29 -[FatherViewModel insertItemsUpdatingExisting:intoVMItems:] (FatherViewModel.m:418)
 16 MYAPP                     0x000f9cfd __39-[FatherViewModel updateItems:failure:]_block_invoke_3 (FatherViewModel.m:281)
 17 libdispatch.dylib              0x3a4718cb _dispatch_call_block_and_release + 10
 18 libdispatch.dylib              0x3a47ada3 _dispatch_root_queue_drain + 834
 19 libdispatch.dylib              0x3a47bcd7 _dispatch_worker_thread3 + 94
 20 libsystem_pthread.dylib        0x3a5d2e31 _pthread_wqthread + 668

这里是我的layoutSubview代码:

- (void)layoutSubviews {
    [super layoutSubviews]; // Sometimes crashed here

    CGFloat contentLeft = kTextInsets.left;

    BOOL isReply = self.editorialCommentData.inReplyToCommentId != 0;

    if (isReply) {
        contentLeft += kAuthorLeftInset + self.authorImageView.frameWidth;
    }

    self.authorImageView.frameOrigin = CGPointMake(contentLeft, kContentInsets.top);

    self.votesLabel.frameWidth = 200; // Sometimes crashed here
    [self.votesLabel sizeToFit];

    self.votesLabel.frameTop = self.authorImageView.frameTop - 1.5f;
    self.votesLabel.frameRight = self.contentView.bounds.size.width - kContentInsets.right;

    <.....more code here.....>
}

我认为这是内存管理问题。

Answer 1

好的!我修好了它。来自 Marco 关于 layoutSubviews 方法的评论:“您不应该直接调用此方法。如果您想强制布局更新，请在下一次绘图更新之前调用 setNeedsLayout 方法来执行此操作。”我刚刚将layoutSubviews更改为layoutIfNeeded方法:

+ (CGFloat)heightForEditorialCommentData:(EditorialCommentVMData *)editorialData
{
    EditorialCommentCell * cell = [EditorialCommentCell instanceCell];
    [cell applyViewModelData:editorialData];
    [cell layoutIfNeeded];
    return cell.commentTextLabel.frameBottom + kTextInsets.bottom;
}

摘自Apple关于layoutIfNeeded的文档:

Use this method to force the layout of subviews before drawing. Using the view that receives the message as the root view, this method lays out the view subtree starting at the root.